EFFECT OF ACACIA GUM ON BARE ROOT NURSERY CROPS AND IN
CUTTING PROPAGATION
Except where reference is made to the work of others, the work described in this thesis is
my own or was done in collaboration with my advisory committee. This thesis does not
include proprietary or classified information.
________________________________________
Sarah Frances Creel
Certificate of Approval:
___________________________ ___________________________
J. Raymond Kessler, Jr. J. David Williams, Chair
Associate Professor Professor
Horticulture Horticulture
___________________________ ___________________________
Kenneth Tilt Floyd M. Woods
Extension Specialist/ Professor Associate Professor
Horticulture Horticulture
____________________________
Stephen L. McFarland
Dean
Graduate School
EFFECT OF ACACIA GUM ON BARE ROOT NURSERY CROPS AND IN
CUTTING PROPAGATION
Sarah Frances Creel
A Thesis
Submitted to
the Graduate Faculty of
Auburn University
in Partial Fulfillment of the
Requirements for the
Degree of
Master of Science
Auburn, Alabama
August 7, 2006
iii
EFFECT OF ACACIA GUM ON BARE ROOT NURSERY CROPS AND IN
CUTTING PROPAGATION
Sarah Frances Creel
Permission is granted to Auburn University to make copies of this thesis at its discretion,
upon the request of individuals or institutions and at their expense. The author reserves
all publication rights.
_______________________________
Signature of Author
_______________________________
Date of Graduation
iv
THESIS ABSTRACT
EFFECTS OF ACACIA GUM ON BARE ROOT NURSERY CROPS AND IN
CUTTING PROPAGATION
Sarah Frances Creel
Master of Science, August 7, 2006
(B.S., Auburn University 2004)
72 Typed Pages
Directed by J. David Williams
The effects of acacia gum on bare root ?Karl Sax forsythia? (Forsythia ?
intermedia ?Karl Sax?) and ?Merrill? magnolia (Magnolia stellata ?Merrill?) were
examined, along with the effects of acacia gum on ?Merlot? Virginia sweetspire (Itea
virginica ?Merlot?); ?Sky Pencil? holly (Ilex crenata ?Sky Pencil?); ?Daisy? gardenia
(Gardenia jasminoides ?Daisy?) in cutting propagation. Tests were conducted to: (1)
assess the efficiency of acacia gum in inhibiting the loss of water throughout storage of
bare root nursery crops, (2) examine the effects of the acacia gum on post transplant
growth of bare root Forsythia ? intermedia ?Karl Sax? and Magnolia stellata ?Merrill?,
and (3) examine the effectiveness of acacia gum in preventing desiccation during storage
and rooting of cuttings.In the bare root study, plants treated with acacia gum had more
growth than those treated with the traditional methods of peat and hydrophilic polymer in
some cases. It may somewhat reduce water loss of the plants during storage though
v
further testing is necessary to investigate reasons for inconsistent results. Success of
acacia gum was highly variable between the two species and acacia gum concentrations.
Acacia gum did not prevent the loss of water of cuttings during propagation. Furthermore
it was found to harm cuttings with increased concentration.
vi
ACKNOWLEDGMENTS
The author would like to express sincere thanks and appreciation to Dr. Williams
Dr. Kessler, Dr. Tilt, and Dr. Woods for all of their knowledge, guidance, and
encouragement. I would also like to give special thanks to my fianc?, Bryan Gill, for his
endless hours of help, along with his love, support, and prayers. I would like to thank my
sister Rachel Creel. I couldn?t have done it without you! Also, thanks to my parents
Randall and Janice Creel and also to David and Ginger Gill for their labor, love and
prayers. Most importantly, I would like to offer my utmost thanks to God for the
opportunity to attend graduate school and His constant presence and guidance every step
of the way.
vii
Style of journal used: Journal of Environmental Horticulture
Computer software used: Microsoft Word 2002, Excel 2002, SAS 8.2
viii
TABLE OF CONTENTS
LIST OF TABLES???????????????????????????.ix
LIST OF FIGURES??????????????????????????....xi
I. INTRODUCTION AND LITERATURE REVIEW???????...????1
II. EFFECTS OF ACACIA GUM ON BARE ROOT NURSERY CROPS???..19
III. EFFECTS OF ACACIA GUM IN CUTTING PROPAGATION??????.34
IV. FINAL DISCUSSION?????..?????????????????60
ix
LIST OF TABLES
CHAPTER II
1. Effect of cooler time and root treatment on
percent water
of forsythia (Forsythia ? intermedia
?Karl Sax?) after storage in a cooler at 38F (3.3C)...............................................29
2. Effect of cooler time on lateral shoot number
and shoot length of forsythia (Forsythia ? intermedia
?Karl Sax?) after storage in cooler at 38F (3.3C)...................................................30
3. Effect of root treatment on lateral shoot number of
forsythia (Forsythia ? intermedia ?Karl Sax?) after
storage in a cooler at 38F (3.3C)?...?????????????????.31
4. Effect of root treatment on shoot length of magnolia
(Magnolia stellata ?Merrill?) after storage in a cooler
at 38F (3.3C)??????... ????????????????.???.32
5. Effect of cooler time on lateral shoot number
of magnolia (Magnolia stellata ?Merrill?) after
storage in cooler at 38F (3.3C)???????????????????..33
CHAPTER III
1. Effect of number of days in cooler on root dry weight,
shoot dry weight, and root rating of Virginia Sweetspire
(Itea virginica ?Merlot?) cuttings under either intermittent
mist or humidity tent propagation after storage in a cooler at
38F (3.3C)???????????????????????????..51
2. Effect of Acacia gum concentration, number of days in
cooler, and propagation method on percent rooting of Virginia
Sweetspire (Itea virginica ?Merlot?) cuttings under either
intermittent mist or humidity tent propagation after storage
in a cooler at 38F (3.3C)??????????????????????52
x
3. Effect of Acacia gum concentration on shoot dry weight of
Sky Pencil holly (Ilex crenata ?Sky Pencil?) cuttings under either
intermittent mist or humidity tent propagation after storage in
a cooler at 38F (3.3C)???????????................................................53
4. Effect of Acacia gum concentration and number of days
in cooler on root dry weight of Sky Pencil holly
(Ilex crenata ?Sky Pencil?) cuttings under either intermittent
mist or humidity tent propagation after storage in a cooler at
38F (3.3C)?????????????????????????.??.54
5. Effect of Acacia gum concentration and number of days in
cooler on root rating of Sky Pencil holly (Ilex crenata
?Sky Pencil?) cuttings under either intermittent mist or
humidity tent propagation after storage in a cooler at
38F (3.3C).......................................................................................................?...55
6. Effect of Acacia gum concentration on percent rooting of
Sky Pencil holly (Ilex crenata ?Sky Pencil?) cuttings under
either intermittent mist or humidity tent propagation after
storage in a cooler at 38F (3.3C)????????.??????????...56
7. Effect of Acacia gum and number of days in cooler on shoot
dry weight of Gardenia (Gardenia jasminoides ?Daisy?)
cuttings under either intermittent mist or humidity tent
propagation after storage in a cooler at
38F (3.3C)???????????????????????????..57
8. Effect of Acacia gum concentration and number of days
in cooler on root rating of Gardenia (Gardenia jasminoides
?Daisy?) cuttings under either intermittent mist or humidity
tent propagation after storage in a cooler at
38F (3.3C)??.??.???????????????????????58
9. Effect of Acacia gum concentration, number of days in cooler,
and propagation method on percent rooting of Gardenia
(Gardenia jasminoides ?Daisy?) cuttings under either intermittent
mist or humidity tent propagation after storage in a cooler at
38F (3.3C)???????????????????????????..69
xi
LIST OF FIGURES
CHAPTER III
1. Root ratings for Virginia Sweetspire (Itea virginica ?Merlot?)???????.40
2. Root ratings for ?Sky Pencil? holly (Ilex crenata ?Sky Pencil?)???????40
3. Root ratings for ?Daisy? gardenia (Gardenia jasminoides ?Daisy?)?????..41
1
CHAPTER I
INTRODUCTION AND LITERATURE REVIEW
Bare Root Nursery Crops
According to the Economic Research Service (ERS), nursery crops are defined as
?woody perennial plants that are usually field-grown in containers or in-ground.? These
include ornamental trees, shrubs, vines, groundcovers, and also fruit and nut trees.
Nursery crops are mainly used in landscaping, and are classified as evergreen, deciduous,
or nursery stock. Various numbers of plants are grown as liners in pots or trays, and some
are grown in fields to be harvested balled and burlapped or bare-root. Bedding plants,
garden plants, flowering plants, foliage plants, and cut flowers are considered floriculture
crops. Floriculture crops are mainly herbaceous and are usually grown in flats, trays,
pots, or hanging baskets (11). Many herbaceous perennials are also harvested and
handled bare-root (12). Nursery crops and floriculture crops are collectively known as
the Green Industry. In 2002, Green Industry sales reached $13.8 billion in the U.S., and
were estimated at $14.3 billion in 2003. Greenhouse and nursery crops are considered the
fourth largest crop group, and constitute one third of the total farm cash receipts from
horticulture crops nationally (9,10).
Due to the problem of root desiccation, plants are primarily shipped balled and
burlapped or in containers. Shipping is very expensive for these plants because of the
2
weight of the soil (10). Many plants are harvested bare root to they reduce the expense of
shipping plants with soil. Also, the loss of valuable topsoil from production fields is a
factor that requires more bare-root harvesting (12). For these reasons, bare-root plants are
considered to be the most economical nursery stock (10). Large wholesale and mail-order
nurseries harvest a large number of trees, shrubs, and herbaceous perennials bare-root in
order to reduce shipping costs (12). Also, export of plants require roots to be soil free and
shipping distance and government regulations increase the time exposure for desiccation
and quality reduction of the plants (2).
Problems do exist with bare-root harvesting and shipping that limit widespread
application. Desiccation during post-harvest handling and storage is the major problem
with bare-root plants (29). Desiccation stress is considered the main cause of inadequate
regrowth of bare-root nursery stock (25). In addition, dessication can cause poor
performance and even plant death. Bare-root plants can be subjected to water loss during
harvesting, processing, storage, shipping, and planting (12). Plants subject to desiccation
during any of these phases are likely to have reduced growth potential and poor quality
after transplanting (5).
Extensive research has documented methods and products to reduce post harvest
desiccation of bare-root nursery stock. Current research has shown that success of a
number of species can be improved when plants are harvested at certain times of year
when desiccation tolerance is highest. This tolerance usually occurs in January or
February when the plants are dormant (13,25). One study was undertaken to determine
the seasonal variation of desiccation tolerance in bare-root plants. Three bare-root
deciduous species were tested for desiccation tolerance at monthly harvest intervals from
3
September 1990 through April 1991. The trees tested were red oak (Quercus rubra L.),
most tolerant to desiccation, Norway maple (Acer platanoides L.), and Washington
hawthorn (Crataegus phaenopyrum Med.), which are less tolerant. January and February
were months of maximum desiccation tolerance for all three tree species (13). The
problem with harvesting during dormancy is that digging can be difficult or even
impossible because of frozen soil in some areas (12).
Other studies have measured the success of using polyethylene wraps around
roots in storage. A study by Lefevere et al. (19) indicated that polyethylene provides
sufficient protection from water loss. The study showed that plants can be stored up to 7
months using polyethylene. A limiting factor with polyethylene is that it is labor intensive
(12). Lefevere?s study also mentioned that desiccation is still possible using any storage
technique that leaves the shoots exposed. Bates et al. (5) analyzed the impact of cold
storage treatments on the desiccation of bare-root Norway maple and Washington
hawthorn by measuring shoot and root water potentials. Stems of the hawthorn were
more susceptible to desiccation during cold storage than maple stems. Roots of both
species were prone to water loss during cold storage. The research showed that while
precautions should be taken to protect the roots of all bare-root plants from desiccation,
desiccation sensitive plants need both shoot and root protection to reduce water loss.
Clay dipping has also been used in attempt to prevent desiccation of white spruce,
white pine, and red pine but this method was observed to be of no benefit to any of the
three species, and even damaging to survival and growth of some plants (24).
Waxes and antitranspirants have been tested for the reduction of water loss. In a
study by Simpson (30), six antitranspirants, XEF-4-3561, Wilt Pruf, Plant Gard, Folicote,
4
Clear Spray, and Vapor Gard, were applied to the stems and foliage of container grown
lodgepole pine (Pinus contorta Doug.), white spruce (Picea glauca (Moench) Voss),
western hemlock (Tsuga heterophylla (Raf). Sarg.), and douglas-fir (Pseudotsuga
menziesii (Mirb.) Franco). Only XEF-4-3561 and Wilt Pruf, were successful in reducing
water loss of lodgpole pines. On the other hand, all six antitranspirants had adverse
effects on the other three plant species in the experiment. Antitranspirants either reduced
plant performance, photosynthesis, or caused plant death. Waxes have also been
successful in reducing desiccation in some species but when tested on roses, were found
to be ineffective (29).
Schuch et al. (29) performed a study on growth and flowering of bare-root roses
(Rosa) after dipping canes in hot wax, or in one of three film forming anti-transpirants:
Moisturin, Glascol, and Alcoprint. Plants were stored for 13 weeks at -2C after treatment.
Plants treated with hot wax resumed growth faster than control plants and faster than
plants treated with antitranspirants. More than 60% of plants treated with hot wax had
severe damage and dieback, whereas less than 20% of plants treated with antitranspirants
were damaged. Hot wax treatment was the most effective in reducing water loss, because
it reduced weight loss from stem sections by 85% in comparison to the control.
Antitranspirant treatments reduced weight loss by 27% in comparison to control. The
disadvantage of hot wax treatment is moderate to severe cane damage and dieback
occured, therefore it is not recommended for use on bare-root plants.
Englert et al. (13) studied the effects of 20 film-forming antidesiccant compounds
on 10 cm stem sections of Washington hawthorn and maple seedlings. Of the 20
antidesiccants used, 8 that performed well on the stems were applied as a dip to roots and
5
shoots of bare root Washington hawthorn and Norway maple seedlings. Moisturin was
the most effective in reducing water loss as well as improving survival and performance
during re-establishment. Plants treated with Moisturin retained 80% more water than
control plants. Washington hawthorn, a species sensitive to dessication, was exposed to
severe drought conditions and treated with Moisturin. These plants had the highest
survival, least plant dieback, and highest root growth ratings of the antitranspirants tested,
demonstrating that Moisturin can be effective in reducing post harvest desiccation stress
in plants sensitive to desiccation.
Carbohydrate depletion during storage is also a concern with bare root nursery crops.
Carbohydrates serve as the energy source for growth and plant cellular metabolism.
Stored seedlings depend on carbohydrate reserves for cellular respiration and to repair
damaged tissues. If subsequent carbohydrate reserves are unable to meet the respiratory
requirement during cold storage and planting, the plant will die. (21)
Cutting Propagation
A common method of rapidly increasing product numbers in the nursery industry
today is vegetative propagation by stem cuttings. Vegetative propagation is preferred
over seed propagation because plants resulting are clones of the parent plant. Therefore,
characteristics such as plant height, plant form, and flowering are maintained in the
product, while seed propagation often results in genetic variability. Vegetative
propagation involves obtaining plant tissue segments from stock plants and placing them
in a rooting environment with the expectation that roots will develop and thus produce
independent plants.
6
In today?s containerized nurseries, many cuttings are propagated using
intermittent mist. This type of system maintains high humidity environment by
producing droplets of fine mist that maintain a film of water covering the foliage of the
cuttings. Water on the leaf surface evaporates instead of the internal water from leaf
tissues. Misting reduces water loss from cuttings by lowering ambient leaf and air
temperature and raising the relative humidity thus reducing transpiration loss. The
frequency and amount of misting necessary to maintain a film of water on the foliage
without over or under watering is influenced by the environment. Cloudy days with low
light intensity and high relative humidity require less frequent misting, while sunny days
with high light intensity and low relative humidity require more frequent misting. If the
propagator does not react to these changing conditions and make the necessary
adjustments to mist frequency and amount, under application of mist can result in
moisture stress and delayed rooting or death, while over applied mist causes dripping
from the foliage keeping the rooting medium saturated, and resulting in rotting of the
cuttings. Constant presence of water on the leaves causes rapid depletion of essential
nutrient reserves from cuttings. Intermittent misting lowers medium temperature, which
can produce suboptimal temperatures that may reduce root growth (14).
The process of using intermittent mist rooting system requires a number of steps
that increase labor costs. These steps include taking cuttings, trimming cuttings to the
appropriate length, wounding, filling flats, dipping cuttings in hormones and sticking,
cleaning and maintaining mist system, removing rooted cuttings from mist and potting
into appropriate containers, transporting containers, and cleaning benches and pots
following removal (36).
7
Another problem with cutting propagation is that when large numbers of cuttings
are harvested from stock plants time is crucial. Cuttings require storage in a cooler for a
certain period of time before the scheduled labor can place them in the propagation
environment. Storage of unrooted cuttings can be effective, though little is known about
the practical side of storing cuttings on a commercial scale. Storage duration depends on
the storage conditions such as temperature and relative humidity, conditions of cuttings,
and species. Water loss, dry matter loss, and disease incidence must be minimized.
Optimal relative humidity must be almost 100%, and optimal temperature must be as low
as tolerable as determined by species. Also, low oxygen and ethylene levels are beneficial
in maintaining ability to root. The question remains of how long cuttings can be stored
practically in a forced-air cool chamber with plastic covering. (6)
According to Whitcomb and Davis, a possible solution is the use of intermittent
misting with antitranspirants to coat the surface of leaves and stems of cuttings, thereby
reducing water loss and possibly the need for continuous misting. Results of one study
indicated that the use of antitranspirants on Podocarpus macrophylla D. Don and
Juniperus chinensis Hort. Ex. Endl ?Hetzi? produced better cuttings than those rooted
under mist. This study showed that for some plants misting was not required. Cuttings
can be inserted directly in growing medium with necessary nutrients incorporated, thus
saving time and increasing cutting growth by eliminating the need to transplant later.
Additionally, problems of disease and leaching of nutrients from leaves may be reduced
or eliminated. Use of antitranspirants could reduce the number of laborious steps
associated with mist propagation and also reduce overall cost of production (36).
8
The effectiveness of antitranspirants in maintaining plant quality has been
evaluated on many different plant species with various application times, methods, and
conditions. For example, the effectiveness of antitranspirants were evaluated in
transplanting oak trees (Quercus virginiana) (17), tissue cultured chrysanthemum
(Chrysanthemum morifolium Ramat ?Bright Golden Anne?) and carnation (Dianthus
caryophyllus L.) (31), postharvest handling of Christmas trees (Abies fraseri (Pursh)
Poir.), and (Juniperus virginiana L.) (15), cold storage of container grown lodgepole
pine, white spruce, western hemlock, and Douglas fir (30), transplant of impatiens
(Impatiens wallerana Hook.f.) seedlings (16), and dogwood (Cornus florida) (37).
Antitranspirants have also been evaluated on apple trees (Malus domestica Borkh.) (35),
Rabbiteye blueberry (Vaccinium ashei Reade) (3), tomato (Lycopersicon esculentum
Mill. ?Early Giant?) (18), packaged roses (29), bare root nursery trees (13), highway
oleander plantings (Nerium oleander L.) (8), and rooting of cuttings (20,36).
However, the effectiveness of antitranspirants is extremely variable. In tissue
cultured chrysanthemum (Chrysanthemum morifolium Ramat ?Bright Golden Anne?) and
carnatations (Dianthus caryophyllus L.), DC 200 significantly reduced transpiration,
however plants were stunted, whereas other antitranspirants such as Aquawiltless, Clear
Spray, Exhalt 4-10, Folicote, Protec, Vapor Gard, and Wiltpruf, were ineffective
compared to the controls (31). In another study using tomato, antitranspirants increased
water use efficiency without negatively affecting plant growth (18). An experiment
evaluating transplanting live oaks (Quercus virginiana Mill.) in August in central Florida
concluded that the antitranspirant Cloud Cover did not improve survival but did improve
the appearance of the trees after transplanting whereas trees treated with Wilt-Pruf had
9
the highest survival rate (17). An additional factor that affected post harvest stress of
summer-dug Fraser photinia (Photinia ? fraseri) was that the use of Vapor Gard on
morning-dug plants showed a high survival rate even without irrigation. Afternoon
digging with or without irrigation resulted in a low survival rate, however all plants
survived with the use of Vapor Gard plus irrigation in the afternoon (28). One
antitranspirant, Crop-Life, was tested on Fraser fir [Abies faseri (Pursh) Poir.] and eastern
red cedar (Juniperus virginiana L.) to determine its ability to reduce water loss and was
found to be ineffective (15). Six antitranspirants, Plantco, Cloudcover, Dow X2-1337,
Clearspray, Vapor Gard, and Folicote, were used in a study on black spruce. Plantco,
Cloudcover, DowX2-1337, and Vapor Gard reduced transpiration, though Vapor Gard
treated plants showed toxicity symptoms and abnormal bud flushing. Folicote and
Clearspray did not reduce water loss (7). The effects of the antitranspirant, CS-6432, on
oleander (Nerium Oleander L.) in a greenhouse and highway planting were positive. The
study showed that transpiration in potted oleanders in a greenhouse decreased by 25-30%
for two weeks after treatment. The results of the study demonstrated that CS-6432 slowed
the depletion of soil water in highway plantings of oleander (8). In a bare-root rose study
comparing growth and flowering of plants treated with either one of three film-forming
antitranspirants, Moisturin, Glascol, and Alcoprint, or hot wax, wax treated plants
resumed growth faster than control or antitranspirant treatments. Wax treated plants also
performed better in the following two weeks. Fewer antitranspirant treated plants were
damaged than those treated with wax, but the wax treated plants had reduced weight loss
by 85% and the antitranspirants only by 27% (29). Water loss of hydrangea (Hydrangea
macrophylla Ser. ?Improved Merveille?) was reduced by antitranspirants, Elvanol,
10
Folicote, Cloudcover, Vapor Gard, and All Safe (22). Clearspray and Vapor Gard were
effective in a cineraria (Senecio cruentus DC.) study on hot days (23). A study using
Foli-Gard, Vapor Gard, and experimental coating No. 30 on cuttings of Juniperus
chinensis L. ?Hetzi? and Podocarpus macrophylla suggested that the use of
antitranspirants can increase rooting in cutting propagation (36). But in a study using
cuttings of Prunus persica ?Harmony? and ?Cresthaven?, the use of Vapor-Gard
significantly decreased the amount of rooting with or without mist (20). In another
propagation experiment, unfolding of the first leaf of un-misted Epipremnum aureum
(Linden ex Andre) Bunting cuttings was delayed by Folicote. Cuttings taken from stock
plants sprayed with Stressguard resulted in slow growth, while cuttings taken from plants
sprayed with Folicote were not affected (34). Comparison of 5 antitranspirants on Citrus
sinensis L. showed that Mobileaf, Vapor Gard, Nu-Film-17, and Wilt Pruf NCF improved
leaf coatings and prevented weight loss in fruit compared to the controls. This study also
concluded that Mobileaf and Vapor Gard decreased the use of water by containerized
trees, Mobileaf for 2 months and Vapor Gard for 5 (1). A study on Camellia sinensis L.
showed that the antitranspirant phenyl mercuric acetate reduced transpiration for about
20, with lessening intensity as each day passed. The spray reduced vegetative growth of
immature plants under drought and non-drought conditions, and yield of mature plants
under drought conditions (26).
11
Acacia gum
A new possibility for enhancing the post harvest shelf life of bare root plants is a
naturally occurring preservative known as acacia gum.
Acacia gum, also known as gum Arabic, is defined as ?the gummy exudate
flowing naturally or obtained by incision of the trunk and branches of Acacia senegal
Willd. and other species.? Acacia gum is unique in that it is soluble at high
concentrations in water (32). It consists of polysaccharides and calcium, magnesium, and
potassium salts, which upon hydrolysis generates glalactose, arabinose, rhamnose and
glucuronic acid (27). There are currently about 1200 known species of Acacia and they
vary considerably in gum quality and usage (4). The gum is used as a food hydrocolloid,
natural emulsifier, flavor encapsulator, stabilizer, texturizing agent, and source of soluble
fiber in low calorie drinks (27). It is also used to clarify wine, also used as an adhesive,
and to encapsulate pharmaceuticals. Lower quality grades of gum are used in printing,
textiles, and in the production of explosives (4). Currently Auburn University is
conducting research to evaluate the potential use of acacia gum to preserve
microorganisms. Acacia gum is used to isolate and preserve a microorganism in a
suspended state without harm. The specimen can later be brought back to its earlier
condition (33). No research has currently evaluated the use of acacia gum in green
industry.
There are no standardized methods of bare root storage and shipping, therefore
there is a need for a more effective postharvest handling product. Acacia gum may offer a
way to reduce desiccation of bare root nursery stock and allow more plants to be
successfully shipped bare-root. This would in turn offer more savings to industry and
12
consumers. Acacia gum may also have use in cutting propagation industry. A new, more
efficient way to reduce water loss of cuttings after harvest and during rooting could help
solve the problems and costs associated with mist systems and cutting propagation
without damaging the cuttings. The objective of this research was to evaluate the
effectiveness of Acacia gum in reducing water loss during storage of bare root nursery
crops and in cutting propagation.
13
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14
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15
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18. Kobbia, T. E., and A. Ibrahim. 1986. Effect of antitranspirants and long-chain
alcohols on water use efficiency and growth of tomato plants. Acta Hort. 190:281-289.
19. Lefevere, R., A. Cameron, and N. Peterson. 1991. Influence of moisture loss during
storage on new growth of conifer seedlings. J. Environ. Hort. 9:92-96.
20. Lyons, Jr. C. G., R. E. Byers, and K. S. Yoder. 1985. Rooting of Semi-Hardwood
Peach cuttings as affected by basal fungicide, mist, and anti-transpirant treatments. J.
Environ.Hort. 3:10-11.
16
21. Marshall, John D. 1985. Carbohydrate status as a measure of seedling quality. p.49-
58. In: Duryea M. L. (editor). Proceedings: Evaluating Seedling Quality: Principles,
Procedures, and Predictive Abilities of Major Tests. Workshop held October 16-18, 1984.
Forest Research Laboratory, Oregon State University, Corvallis, OR.
22. McDaniel, G. L. 1985. Transpiration in hydrangea as affected by antitranspirants and
chlormequat. HortScience 20:293-296.
23. McDaniel, G. L., and G. L. Bresenham. 1978. Use of antitranspirants to improve
water relations of cineraria. Hortscience 13:466-467.
24. Mullin, R., and W. Bunting. 1979. Another look at clay dipping of bare root nursery
stock. For. Chronicle 55:183-188
25. Murakami, P., T. Chen, and L. Fuchigami. 1990. Desiccation tolerance of deciduous
plants during post harvest handling. J. Environ. Hort. 8:22-25.
26. Nagarajah, S., and G. B. Ratnasooriya. 1977. Studies with antitranspirants on tea
(Camellia sinensis L.). Plant and soil 48:185-187.
27. Phillips, G. O., 1998. Acacia gum (gum Arabic): A nutrional fibre: Metabolism and
calorific value. Food Additives Contaminants 15:251-264.
17
28. Ponder, H. G., C. H. Gilliam, and H. J. Dawes. 1983. Factors affecting postharvest
stress of summer-dug photinia. Hortscience 18:83-85.
29. Schuch, U., J. Karlik, and C. Harwood. 1995. Antidesiccants applied to packaged rose
plants affect growth and field performance. Hortscience 30:106-108.
30. Simpson, D.G.1984. Filmforming antitranspirants: Their effects on root growth
capacity, storability, moisture stress avoidance, and field performance of containerized
conifer seedlings. For. Chronicle 60:335-339.
31. Sutter, E. G., and M. Hutzell. 1984. Use of humidity tents and antitranspirants in the
acclimatization of tissue-cultured plants to the greenhouse. Scientia Horticulturae 23:303-
312.
32. Thevenet, F. 1995. Encapsulation and controlled release of food ingredients.
American Chemical Society. Washington, DC.
33. Vodyanoy, V.J., J.M. Barbaree, B.A. Chin, W.C. Neely, S.T. Pathirana, T.D. Braden.
2001. Use of Acacia gum to isolate and preserve biological material. United States Patent
and Trademark Office. http://patft.uspto.gov/netacgi/nph-
Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrc
hnum.htm&r=1&f=G&l=50&s1=7022514.PN.&OS=PN/7022514&RS=PN/7022514.
(Last accessed April 2006).
18
34. Wang, Y. T., K. H. Hsiao, and L. L. Gregg. 1992. Antitranspirant, water stress, and
growth retardant influence growth of golden pothos. HortScience 27:222-225.
35. Weller, S. C., and D. C. Ferree. 1978. Effect of a pinolene-base antitranspirant on
fruit growth, net photosynthesis, transpiration, and shoot growth of ?Golden Delicious?
apple trees. J. Amer. Soc. Hort. Sci. 103:17-19.
36. Whitcomb, C. E., and L. T. Davis Jr. 1970. Antitranspirants ? a better way to root
cuttings? Amer. Nurseryman. 132:100-101.
37. Williams, J. D., H. G. Ponder, and C. H. Gilliam. 1987. Reducing moisture stress in
Cornus florida. J. Environ. Hort. 5:131-133.
19
CHAPTER 2
EFFECTS OF ACACIA GUM ON BARE ROOT NURSERY CROPS
Abstract
The effects of acacia gum were evaluated on bare root Forsythia ? intermedia ?Karl Sax?
and Magnolia stellata ?Merrill?. Plants received one of six root treatments: roots dipped
in water, roots packed in moist sphagnum peat moss, roots packed in hydrophilic
polymer, and whole plant dipped for 5 seconds in 5%, 10%, and 20% concentrations of
acacia gum. Cuttings were then stored in a walk-in cooler at 38F (3.3C) for 0, 3, 6, 9, or
12 weeks. Acacia gum treatments were more successful at concentrations of 5% and 10%
than treatments of peat and hydrophilic polymer for forsythia, and at 20% for magnolia.
Increasing cooler time caused a decrease in growth of both forsythia and magnolia.
Index words: sphagnum peat moss, hydrophilic polymer
Species used in this study: Karl Sax forsythia (Forsythia ? intermedia ?Karl Sax?) and
Merrill magnolia (Magnolia stellata ?Merrill?)
20
Significance to the Nursery Industry:
Nursery growers often harvest and transport plants bare root. The loss of water
from bare root plants during storage and shipping is often problematic. Desiccation
during post harvest handling can result in reduced plant performance and even death after
out planting. There are many commercial products on the market today that are used in
an attempt to reduce desiccation of bare root crops, but they all have their disadvantages.
There is a need for an improved product on the market. This study evaluated the ability of
acacia gum to reduce water loss of bare root forsythia and magnolia. Different rates of
acacia gum were tested against two standard nursery products, sphagnum peat moss and a
hydrophilic polymer. Acacia gum treatments were equal or better than the traditional
treatments of peat and hydrophilic polymer in some cases, though success varied between
species and acacia gum concentrations. Further testing of acacia gum at different rates
with different species is necessary before any recommendation should be made to the
nursery industry
Introduction
Bare-root plants are considered to be the most economical nursery stock (3).
Many plants are harvested and transported bare root because of the expense of shipping
plants with soil. The loss of valuable topsoil from production fields is a factor that
requires alternative methods of bare-root harvesting. Large wholesale and mail-order
nurseries import and harvest a large amount of trees, shrubs, and herbaceous perennials
bare-root (4). Also, export of plants requires roots to be soil free. Commercial shipping
21
and governmental regulations increase time exposure for desiccation and quality
reduction of these plants (1).
Desiccation during post-harvest handling and storage is the major problem with
bare-root plants that prevents its more widespread use (10). Desiccation stress is
considered the main cause of reduced regrowth of bare-root nursery stock (8) and can
result in inadequate performance and senescence. Bare-root plants can be subjected to
water loss during harvesting, processing, storage, shipping, and planting (4). Plants
subject to desiccation during any of these phases are likely to have reduced growth
potential and quality after transplanting (2).
Extensive research has documented methods and products to reduce post harvest
desiccation of bare-root nursery stock. Success of a number of species can be improved
when plants are harvested at certain times of year when desiccation tolerance is highest.
This tolerance usually occurs in January or February when the plants are dormant (5,8).
Other studies have measured the success of using polyethylene wraps around roots in
storage. A study by Lefevere et al. (6) indicated that polyethylene provides sufficient
protection from water loss. Potentially, plants can be stored up to 7 months using
polyethylene. A limiting factor with polyethylene is that it is labor intensive (4).
Lefevere?s study also mentioned that desiccation is still possible using any storage
technique that leaves the shoots exposed.
Clay dipping has been used in attempt to reduce desiccation of white spruce,
white pine, and red pine however this method failed to alter water loss in any of the three
species, and in certain instances damage occurred (7). Waxes and antitranspirants have
also been evaluated for the reduction of water loss. Simpson (11) used six
22
antitranspirants were tested on container grown lodgepole pine (Pinus contorta Doug.),
white spruce (Picea glauca (Moench) Voss), western hemlock (Tsuga heterophylla (Raf).
Sarg.), and douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). Two of the six
antitranspirants tested were successful in reducing water loss of lodgepole pines. On the
other hand, all six antitranspirants had adverse effects on white spruce, western hemlock,
and douglas-fir. The antitranspirants reduced plant performance, reduced photosynthesis,
or caused plant death. Waxes have been successful in reducing desiccation in some
species however when tested on rose canes, moderate to severe cane damage and plant
dieback was observed (10).
A new possibility for enhancing the post harvest shelf life of bare root plants is a
naturally occurring preservative known as acacia gum. Acacia gum is also known as gum
Arabic. It is defined as ?the gummy exudate flowing naturally or obtained by incision of
the trunk and branches of Acacia senegal Willd. and other species.? Acacia gum is
unique in that it is soluble at a very high concentration in water (12). Auburn University
is conducting research to evaluate the potential use of acacia gum to preserve
microorganisms. Acacia gum is used to isolate and preserve a microorganism in a
suspended state without harm. The specimen can later be brought back to its earlier
condition (13). No reported trials have been cited of the use of acacia gum in green
industry. The objective of this study was to evaluate the effectiveness of acacia gum in
reducing water loss during storage of bare root nursery crops, and to test the effects of the
acacia gum on post transplant growth of bare root Forsythia ? intermedia ?Karl Sax? and
Magnolia stellata ?Merrill?.
23
Materials and Methods
On January 28, 2005, Karl Sax forsythia (Forsythia ? intermedia ?Karl Sax?) and
Merrill magnolia (Magnolia stellata ?Merrill?) bare-root cuttings were received in
Auburn, AL from Schaefer Nursery, Winchester, TN. Cuttings arrived packaged in
cardboard boxes surrounded with moist sphagnum peat moss, wrapped in plastic, and
topped with shingle tow. Upon arrival boxes were placed in a walk-in cooler set at 3.3C
(38F) at Paterson Greenhouse complex on Auburn University campus. Cuttings were
examined and found to be in excellent condition. Transit time was approximately 4 days.
Treatment of the cuttings began on February 1, 2005. Roots were surface
sterilized by dipping into a 3.8 liter (1 gallon) bucket containing ZeroTol Broad Spectrum
Algaecide/Fungicide (Biosafe Systems, Glastonburg, CT) for five seconds at the labeled
rate of 78 g per 3.8 liter (2.75 oz per gallon) of water. Cuttings were divided into groups
of 5 and randomly assigned one of six root treatments. All treatments included placing
roots in 3.8 liter (1 gallon) plastic bag wrapped with a rubber band leaving shoots
exposed. Treatments were as follows: 1) roots dipped in water (0% water control), 2)
roots packed in moist sphagnum peat moss, 3) roots packed in 25 oz (750 ml) of wet
hydrophilic polymer Terra Sorb Super Absorbent Planting Gel, Medium grade (Plant
Health Care Inc., Pittsburg, PA), and treatments 4, 5, and 6) whole plant dipped for 5
seconds in 5%, 10%, and 20% acacia gum (Instagum AS, CNI, Normandy, France),
respectively. Six cutting treatments of the 2 species were divided into four different
storage durations with 10 plants per treatment to be removed at 4 different intervals:
group 1 after 3 weeks of storage (February 21, 2005), group 2 after 6 weeks of storage
(March 14, 2005), group 3 after 9 weeks of storage (April 4, 2005), group 4 after 12
24
weeks of storage (April 25, 2005). Control consisted of 5 plants of each species potted on
February 1, 2005 and receiving no treatment or cold storage time.
Acacia gum was previously mixed on January 31, 2005 using Fisher Scientific
stirrers (Fisher Scientific International Inc., Hampton, NH). The acacia gum was mixed
on a weight/volume basis. The 5%, 10%, and 20% solutions were mixed using 100g (3.5
oz), 200g (7.1 oz.), and 400g (14.1 oz) of acacia gum and 1900 mL (0.5 gal), 1800 mL
(0.48 gal), and 1600 mL (0.42 gal) of deionized water, respectively. Solutions were
continuously mixed for 24 hours.
After treatment, cuttings were placed in plastic boxes according to their storage
time, covered in clear plastic, and stored in a walk-in cooler set at 3.3C (38F). At the end
of each storage time plants were removed from the cooler and divided to two groups (five
plants of each treatment). The first group of cuttings was washed; roots removed,
weighed on a Mettler AE 100 balance (Thomas Scientific, USA) and placed in labeled
paper bags. Roots were subsequently dried in a drying oven set at 70C (158F) and
weighed again. The second group of cuttings were washed and potted into containers for
growth analysis using a media mix of 0.45 cubic meters (16 cu ft) of pine bark and .057
cubic meters (2 cu ft) of sand. Also included in the mix was 4.22 kg (9 lbs 5 oz) of
Polyon 17-6-12 fertilizer (Pursell, Sylacauga, AL), 1.5 kg (3 lbs 4 oz ) of dolomitic
limestone, and 0.45 kg (1 lb) of Micro-max (Scotts, Marysville, OH).
Data collected was dry weight of roots of forsythia and magnolia. Also, the
original shoot lengths of potted magnolia and forsythia were taken and shoot length and
lateral shoot number of plants 4 months after potting.
25
Data were analyzed using PROC GLM in PC-SAS as a split plot design with
preservative treatment as the main plot and cooler time as the sub plot. Trends of acacia
gum rate were analyzed using linear and quadratic orthogonal polynomials, P = 0.05.
Sphagnum peat and hydrophilic polymer were compared to acacia gum treatments using
Dunnett?s Comparison to a control, P = 0.05 (9).
Results and Discussion
Table 1 shows the interaction between date and acacia gum concentration was
significant with percent water of forsythia. There was no trend in percent water after 3
and 12 weeks of storage. There was a quadratic trend in percent water after 6 weeks of
storage with highest values at 5% and 10% acacia gum concentration. There was a linear
and quadratic trend after 9 weeks with highest value at 5% acacia gum. After six weeks
in cooler, percent water at 5% and 10% acacia gum was significantly higher than peat.
After 12 weeks, percent water at 10% acacia gum was significantly higher than peat
(Table 1).
In Table 2, the interaction between date and acacia gum was not significant on shoot
length and lateral shoot number. As cooler time increased, shoot length and lateral shoot
number of forsythia decreased regardless of acacia gum concentration.
Table 3 shows lateral shoot number of forsythia at 5% and 10% acacia gum
concentration was higher than the hydrophilic polymer. There was no significant trend
with increasing acacia gum concentration. The interaction between date and acacia gum
concentration was not significant, which suggests that 5% and 10% acacia gum was
better than hydrophilic polymer regardless of time in cooler.
26
No treatment had any effect on percent water loss of magnolia. The interaction
between date and acacia gum was not significant on shoot length and lateral shoot
number with regard to root treatment. Shoot length of magnolia was significantly higher
at 20% acacia gum concentration than peat. There was no significant trend with
increasing acacia gum concentration (Table 4).
There was no significant interaction between date and acacia gum concentration on
lateral shoot number of magnolia. There was a linear decrease in lateral shoot number of
magnolia with increasing time in cooler (Table 5).
Acacia gum treatments were more effective than peat and hydrophilic polymer in
some cases. The effectiveness of acacia gum treatments varied between species and
acacia gum concentration. Further research is necessary before any recommendation can
be made to the nursery industry.
27
Literature Cited
1. Animal and Plant Health Inspection Service. 2006. Plant Health. 12 June 2006.
.
2. Bates, R., A. Niemiera, and J. Seiler. 1994. Cold storage method affects root and shoot
water potential of bare root hawthorn and maple trees. J. Environ. Hort. 12:219-222.
3. Economic Research Service. 2004a. Floriculture and nursery crops yearbook:
Summary. 9 September 2004.
.
4. Englert, J., L. Fuchigami, and H. Chen. 1993. Bare-root basics. American Nurseryman.
177:56-58, 60-61.
5. Englert, J., K. Warren, L. Fuchigami, and T. Chen. 1992. Antidesiccant compounds
improve the survival of bare root deciduous nursery trees. J.Amer.Soc. Hort.
Sci.118:228-235.
6. Lefevere, R., A. Cameron, and N. Peterson. 1991. Influence of moisture loss during
storage on new growth of conifer seedlings. J. Environ. Hort. 9:92-96.
7. Mullin, R., and W. Bunting. 1979. Another look at clay dipping of bare root nursery
stock. For. Chronicle 55:183-188
28
8. Murakami, P., T. Chen, and L. Fuchigami. 1990. Desiccation tolerance of deciduous
plants during post harvest handling. J. Environ. Hort. 8:22-25.
9. SAS Institute Inc. 1999-2001. Cary North Carolina. Version 8.2. October 8, 2002.
10. Schuch, U., J. Karlik, and C. Harwood. 1995. Antidesiccants applied to packaged rose
plants affect growth and field performance. Hortscience 30:106-108.
11. Simpson, D.G.1984. Filmforming antitranspirants: Their effects on root growth
capacity, storability, moisture stress avoidance, and field performance of containerized
conifer seedlings. For. Chronicle 60:335-339.
12. Thevenet, F. 1995. Encapsulation and controlled release of food ingredients.
American Chemical Society. Washington, DC.
13. Vodyanoy, V.J., J.M. Barbaree, B.A. Chin, W.C. Neely, S.T. Pathirana, T.D. Braden.
2001. Use of Acacia gum to isolate and preserve biological material. United States Patent
and Trademark Office. http://patft.uspto.gov/netacgi/nph-
Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrc
hnum.htm&r=1&f=G&l=50&s1=7022514.PN.&OS=PN/7022514&RS=PN/7022514.
(Last accessed April 2006).
29
Table 1. Effect of cooler time and root treatment on percent water
1
of forsythia
(Forsythia ? intermedia ?Karl Sax?)
2
after storage in a cooler at 38F (3.3C)
Root Treatment
Weeks Peat Hydro-
philic
polymer
0% 5% 10% 20% Significance
3 78.7 83.7 74.3
h
79.2 80.2 80.9 NS
6 64.9 77.2
p
71.5 81.1
p
77.7
p
67.6
Q*
9 96.9 95.7 80.4
ph
96.5 95.3 95.9 L***Q***
12 73.8 78.2 76.5 77.0 88.5
p
82.4 NS
1
(fresh weight - dry weight)/fresh weight x 100
2
Interaction between date and acacia gum significant.
h
Significantly different from hydrophyllic polymer (HP).
p
Significantly different from peat.
30
Table 2. Effect of cooler time on lateral shoot number and shoot
length of forsythia (Forsythia ? intermedia ?Karl Sax?)
1
after
storage in a cooler at 38F (3.3C)
Week 3 6 9 12 Significance
Shoot
number
5.1 3.9 3.6 2.8
L***
Shoot
length
(cm)
40.2 38.3 27.6 17.3
L***
1
Interaction between date and acacia gum concentration not significant.
31
Table 3. Effect of root treatment on lateral shoot number of forsythia
(Forsythia ? intermedia ?Karl Sax?)
1
after storage in a cooler at 38F (3.3C)
Acacia gum Concentration
Root
Treatment
Peat
Hydrophilic
polymer
0%
(water
control)
5% 10% 20% Sig.
Shoot
number
3.8 2.9 3.8 4.8
h
4.2
h
3.8 NS
1
Interaction between date and acacia gum concentration not significant.
h
Significantly different from HP (nursery standard).
32
Table 4. Effect of root treatment on shoot length of magnolia (Magnolia stellata
?Merrill?)
1
after storage in a cooler at 38F (3.3C)
Acacia gum Concentration
Root
Treat-
ment
Peat
Hydro-
philic
polymer
0%
(water
control)
5% 10% 20% Sig.
Shoot
length
(cm)
32.5 36.4 37.7 38.9 37.1 41.3
p
NS
1
Interaction between date and acacia gum concentration not significant.
p
Significantly different from peat (nursery standard).
33
Table 5. Effect of cooler time on lateral shoot number of magnolia
(Magnolia stellata ?Merrill?)
1
after storage in a cooler at 38F (3.3C)
Week 3 6 9 12 Significance
Shoot
number
1.7 1.3 0.8 0.5
L***
1
Interaction between date and acacia gum concentration not significant.
34
CHAPTER 3
EFFECTS OF ACACIA GUM IN CUTTING PROPAGATION
Abstract
The effects of acacia gum were evaluated on cuttings of ?Merlot? Virginia sweetspire
(Itea virginica ?Merlot?), ?Sky Pencil? holly (Ilex crenata ?Sky Pencil?), and ?Daisy?
gardenia (Gardenia jasminoides ?Daisy?). The purpose of this study was to assess the
effectiveness of acacia gum in reducing water loss during storage and rooting of cuttings.
Cuttings were treated with 0%, 5%, 10%, or 20% concentrations of acacia gum and
stored for either 0, 4, 8, or 12 days in a walk in cooler at 38F (3.3C). Data was taken
after 8 weeks under either intermittent mist or a humidity tent. Overall, acacia gum had a
detrimental effect on cuttings, with the exception of Virginia Sweetspire. Rooting
percentage of Virginia Sweetspire was higher at 5%, 10%, and 20% acacia gum
concentration than at 0%, with 10% resulting in the highest rooting percentage. Both
holly and gardenia showed a decrease in shoot dry weight, root dry weight, and percent
rooting as acacia gum concentration increased. Sky Pencil holly also showed a decrease
in root rating with increasing acacia gum percentage. A four day cooler time improved
rooting compared to controls. Longer durations resulted in a decline in rooting. Also,
intermittent mist was more effective in rooting than the humidity tent.
35
Index words: humidity tent, intermittent mist,
Species used in this study: ?Merlot? Virginia sweetspire (Itea virginica ?Merlot?); ?Sky
Pencil? holly (Ilex crenata ?Sky Pencil?); ?Daisy? gardenia (Gardenia jasminoides
?Daisy?)
Significance to the Nursery Industry:
Most growers today use intermittent mist system for vegetative propagation by
stem cuttings. Use of intermittent mist causes many problems for the propagator from
constant regulation to maintenance and extra labor. The purpose of this study was to
evaluate the potential use of acacia gum in reducing water loss during storage and rooting
of cuttings, and therefore reduce the need for intermittent mist. .More cuttings of Virginia
sweetspire treated with acacia gum rooted than those that were not treated with acacia
gum. However, acacia gum had the opposite effect on holly and gardenia and overall, had
a negative impact on the cuttings. Acacia gum is not recommended for use in propagation
of cuttings without further testing. However, storage of cuttings for up to 4 days prior to
sticking had a positive effect on rooting.
Introduction:
A common method of rapidly increasing product numbers in the nursery industry
is vegetative propagation by stem cuttings. In today?s containerized nurseries, many of
these cuttings are propagated using intermittent mist. The frequency and amount of mist
necessary to maintain a film of water covering the foliage without over or under watering
36
is influenced by the environment. Cloudy days with low light intensity and high relative
humidity require less frequent misting, while sunny days with high light intensity and low
relative humidity require more frequent misting. Changing environmental conditions
from sunup to sundown on a given day can mean frequent mist adjustments. If the
propagator does not react to these changing conditions and make the necessary
adjustments to mist frequency and amount, under application of mist can result in
moisture stress and delayed rooting or senescence. Over applications of mist causes
excessive dripping from the foliage keeping the rooting medium saturated, and resulting
in rotting of cuttings. Constant presence of water on the leaves causes rapid depletion of
essential nutrient reserves from the cuttings. Intermittent misting lowers medium
temperature, which can produce suboptimal temperatures that may reduce rooting (1).
Another problem with cutting propagation is that when large numbers of cuttings are
harvested from stock plants time is crucial. Cuttings require storage in a cooler for a
period of time until labor is available to prepare cuttings and place them in the
propagation environment. In addition, the process of using an intermittent mist system
requires a number of steps that increase labor costs. These steps include taking cuttings,
trimming cuttings to the appropriate length, wounding, filling flats, dipping cuttings in
hormone and sticking, cleaning and maintaining mist system, removing rooted cuttings
from mist and potting into appropriate containers, transporting containers, and cleaning
benches and pots following removal (5).
A new possibility for reducing water loss of propagated cuttings is a naturally
occurring preservative known as acacia gum. Acacia gum is also known as gum Arabic.
It is defined as ?the gummy exudate flowing naturally or obtained by incision of the trunk
37
and branches of Acacia senegal Willd. and other species.? Acacia gum is unique in that it
is soluble at high concentrations in water (3). Auburn University is conducting research
to evaluate the potential use of acacia gum to preserve microorganisms. Acacia gum is
used to isolate and preserve a microorganism in a suspended state without harm. The
specimen can later be brought back to its earlier condition (4). No reported trials have
been cited of the use of acacia gum in green industry.
Acacia gum could possibly reduce the need for intermittent mist systems in
cutting propagation. Application of Acacia gum to the leaves and stems of cuttings could
decrease water loss, therefore reducing the need for frequent mist application. This could
ultimately help minimize the problems of over or under watering often associated with
cutting propagation. Acacia gum could also lessen the burden of constantly adjusting the
frequency and amount of mist during changing weather conditions. Acacia gum may
provide an effective way to prevent desiccation of cuttings after harvest during storage
and rooting without damaging the cuttings. The objective of this study was to evaluate
the effectiveness of acacia gum in preventing water loss during storage and rooting of
cuttings.
Materials and Methods
Plant Material. Cuttings were taken (October 4, 2005) of Itea virginica ?Merlot?,
(October 5, 2005) Ilex crenata ?Sky Pencil?, and Gardenia jasminoides ?Daisy?, from
Greenehill Nursery in Waverly, AL.
Cuttings were placed in coolers of ice cold water following collection where they
remained overnight and also during transportation to Paterson Greenhouses at Auburn
38
University, Auburn AL. After overnight storage, cuttings were treated with Acacia gum
(Instantgum AS, CNI, Normandy, France) and stuck at 0, 4, 8, and 12 day intervals and
placed under either intermittent mist or a humidity tent for a total of 8 weeks. The
cuttings treated on day 0 were trimmed from the base to a 10.2 cm (4 in) length. All
leaves were removed from the lower third of each cutting. The basal 1 cm (0.4 in) of each
cutting was wounded and dipped in Hormodin 2 (E.C. Geiger Inc., Harleysville, PA). The
rest of the cutting was then treated by dipping in 0% (water control), 5%, 10%, or 20%
Acacia gum solution. The Acacia gum was mixed on a weight/volume basis. The 5%,
10%, and 20% solution was mixed using 100g (3.5 oz), 200g (7.1 oz.), and 400g (14.1
oz) of acacia gum and 1900 mL (0.5 gal), 1800 mL (0.48 gal), and 1600 mL (0.42 gal) of
deionized water, respectively. Solutions mixed for 24 hours. After treatment, cuttings
were inserted into 606 market flats containing a medium of peat:perlite (1:1 by vol) with
187 g (6.6 oz) of dolomitic lime incorporated. Flats were placed in trays lined with
punctured plastic layered with 0.64 cm (.25 in) of wet sand. Cuttings were then placed
under either intermittent mist covered by a 50% shade cloth or a humidity tent enclosed
in plastic on all sides and then covered with an identical shade cloth. Temperatures under
the tent ranged from 26.7C (80F) to 35C (95F). Intermittent mist operated for 5 sec at 5
min intervals from sunrise to dusk. Both the tent and the mist structures were inside a
greenhouse which was also covered by a 50% shade cloth. Greenhouse temperatures
ranged from 21C (70F) to 26.7 (80F). Cuttings were inserted at 0, 4, 8, and 12 day
intervals were treated with one of the 4 (including control) acacia gum concentrations,
placed in separate labeled Ziploc bags, weighed using a Mettler AE 100 balance (Thomas
Scientific, USA) and stored inside a walk-in cooler at 5.6C (42F) until the appropriate
39
removal date. After cuttings had been stored for the allotted time, they were removed
from the cooler, cut to the proper length, bottom leaves removed, base wounded, treated
with Hormodin 2, and inserted into medium. Light measurements were taken in the
greenhouse and under both structures at different times within the 8 week period. In the
greenhouse the light measurements had an average of 5541 lux. Under humidity tent and
mist, averages were 1498 lux and 2223 lux, respectively. Each group of cuttings was
checked at four weeks from the actual date of insertion to note rooting. Shade cloth was
removed (November 18, 2005) from both the mist and the humidity tent. Also, the
intermittent mist was reset to 5 sec every 10 min. One application of Banrot 40WP (Etri
diazole and Thiophanate-Methyl, The Scotts Company, Marysville,OH), drench at the
labeled rate of 113-340 g per 379 liters (4-12 oz per 100 gal) was applied to control
disease (November 22, 2005).
After 8 weeks, cuttings were harvested and various data recorded. Data taken
included a visual root rating for each species ranging from 0 to 6. Virginia Sweetspire
root ratings were: 0= dead, 1 =alive but no roots, 2 = 1-40 roots, 3 = 40-60 short roots, 4
= 50-70 long roots, 5 = 70-100 roots, through 6 = 100-200 roots. Sky pencil holly root
ratings were as follows: 0 = dead, 1 = no roots, 2 = 1-10 roots, 3 = 10-20 roots, 4 = 20-30
roots, 5 = 30-50 roots, and 6 =50-100 roots. For gardenia, the root ratings were: 0=dead,
1= no roots, 2=1-5 roots, 3=5-10 roots, 4=10-20 roots, 5=20-30 roots, 6=30-50 roots.
40
Figure 1. Root Ratings for Virginia Sweetspire (Itea virginica ?Merlot?)
2 3 4 5 6
0=dead, 1=no roots
Figure 2. Root Ratings for ?Sky Pencil? Holly (Ilex crenata ?Sky Pencil?)
2 3 4 5 6
0=dead, 1=no roots
41
Figure 3. Root Ratings for ?Daisy? Gardenia (Gardenia jasminoides ?Daisy?)
2 3 4 5 6
0=dead, 1=no roots
Other data taken included root dry weight and shoot dry weight. Also, root to shoot ratio
was calculated.
Data were analyzed using PROC GLM in PC-SAS as a split-split plot design with
days in cooler as the main plot, tent as sub plot, and acacia gum treatment as sub-sub-
plot. Trends over days in cooler and acacia gum rate were analyzed using linear and
quadratic orthogonal polynomials, P = 0.05 (2).
42
Results and discussion
Virginia Sweetspire
There was no treatment effect on root to shoot ratio of Virginia Sweetspire cuttings.
There was a significant propagation method x days in cooler interaction for root
root dry weight (RDW), shoot dry weight (SDW), and root rating (RR) for Virginia
Sweetspire cuttings under either mist or humidity tent (Table 1). Under both tent and
mist there was a 22% and 38% linear decrease in SDW of Virginia Sweetspire cuttings,
respectively. There was no change in RDW under tent, but under mist there was a 33%
decrease in RDW. RR of the cuttings showed a 16% and 31% linear decrease under tent
and mist, respectively. SDW, RDW, and RR were higher under mist than tent with 0 days
in the cooler. There was no difference in RR between tent and mist with 4 days of cooler
time. However SDW and RDW were higher under mist than tent with 4 days in the
cooler. With 8 days of cooler time there was no difference between tent and mist with
RDW or RR. SDW under mist was higher with 8 days of cooler time than under tent.
There was no difference in RDW and RR between tent and mist with 12 storage days,
however, SDW under mist was higher than under tent with 12 days (Table 1). Overall,
increasing cooler times had no effect on RDW of cuttings under humidity tent, but had a
negative effect on SDW and RR under humidity tent. Also, increasing cooler times
caused a decrease in SDW, RDW, and RR of Virginia Sweetspire cuttings under mist.
RDW and RR were higher under mist than tent with shorter storage time. SDW was
higher under mist than tent with all storage times.
Table 2 shows that only main effects were significant for rooting percentage of
Virginia Sweetspire. There was a quadratic response with a 39 % increase in rooting
43
percentage with increasing acacia gum rate, the highest percentage being at 10% acacia
gum concentration. There was a 10% linear decrease in rooting percent with increasing
days in cooler. Percent rooting was higher under mist than humidity tent for all the
Virginia Sweetspire cuttings.
Overall results were more positive for Virginia Sweetspire cuttings under mist
than humidity tent. Shoot dry weight, root dry weight, root rating, and rooting percentage
decreased with increased storage time. This indicates that Virginia Sweetspire cuttings
may perform better without cold storage prior to soil insertion. More testing should be
done to determine effects of storage of cuttings prior to insertion. Acacia gum had a
positive effect on rooting percentage of Virginia Sweetspire. 5%, 10%, and 20% were all
higher than 0% Acacia gum, 10% having the highest rooting percentage. Acacia gum
may have been successful in reducing water loss of cuttings of Virginia Sweetspire.
Further testing is necessary to evaluate the effectiveness of Acacia gum of reducing water
loss of Virginia Sweetspire cuttings. It would also be beneficial to test acacia gum on
many different species at different concentrations.
Sky Pencil Holly
Root to shoot ratio of Sky Pencil holly was not affected by any treatment. Table 3
shows that there were propagation x acacia gum concentration interactions for SDW
under mist or tent for Sky Pencil holly cuttings. Also, there was a main effect for days in
cooler. Under both tent and mist there was a 30% linear decrease in SDW. SDW
decreased linearly by 11% after storage in cooler with increasing acacia gum rate. With
0% and 5% acacia gum rates, there was no difference in SDW between tent and mist.
44
With 10% and 20% rates however, SDW was higher under mist than tent. In summary
for Table 3, under both tent and mist, there was a decrease in SDW with increasing acacia
gum rate. SDW decreased with days in cooler as acacia gum rate increased.
Table 4 shows that there were interactions among days in cooler x propagation
method, acacia gum concentration x propagation method, and acacia gum concentration x
days in cooler interactions for root dry weight and root rating under either mist or tent for
Sky Pencil holly cuttings. RDW for the cuttings did not change under mist with
increasing cooler time, and increased by 83% linearly under tent with increasing cooler
time. There was no difference in RDW between humidity tent and mist at 0 and 8 days in
cooler but at 4 and 12 days in cooler RDW was higher under mist. RDW under mist was
not affected by increasing acacia gum rate. However, there was a quadratic response
under the humidity tent with a 99% decrease in RDW from 0% to 20% acacia gum. There
was no difference in RDW between tent and mist at 0%, 5%, and 10% acacia gum rate.
RDW was higher under mist than under tent at 20% acacia gum rate. With increasing
acacia gum rate, there was no change in RDW at 0, 4, and 12 days in cooler. There was
however, a quadratic response at 8 days in cooler with a 50% increase in RDW with
increasing acacia gum concentration. At 0% acacia gum rate, there was a quadratic
response from 0 to 12 days in cooler with a 100% increase in RDW. With 5%, 10%, and
20% there was no change in RDW with increasing cooler time. Root rating increased
linearly by 77% under tent with increasing cooler time, and did not change under mist.
RR was higher under mist than tent at 0, 4, 8, and 12 days in cooler. Under the humidity
tent, there was a quadratic response as acacia gum rate increased with an 87% decrease in
RR. Also, under mist, there was a 15% linear decrease in RR as acacia gum rate
45
increased. At all acacia gum rates, RR was higher under mist than tent. On days 0, 4, 8,
and 12 of cooler time, there was a 40%, 25%, 52%, and 66% linear decrease in RR,
respectively. RR showed a 57% linear increase at 0% acacia gum rate with increasing
days in cooler. There was no change in RR at 5%, 10%, and 20% acacia gum rate with
increasing days in cooler. RDW and RR (Table 4) under humidity tent increased as days
in cooler increased. Both RDW and RR decreased quadratically under tent as % acacia
gum increased. Also, as % acacia gum increased, RR decreased over all cooler times.
RDW and RR at 0% acacia gum increased with increasing cooler times, whereas 5%,
10%, and 20% showed no change with storage in cooler. RR decreased with increasing %
acacia gum at 0, 4, 8, and 12 days in cooler. Finally, RR was higher under mist than
under humidity tent.
There were significant propagation method ? acacia gum concentration interactions
on percent rooting of Sky Pencil holly cuttings under either intermittent mist or humidity
tent after storage in a cooler (Table 5). There was a 100% linear decrease in percent
rooting under humidity tent with increasing acacia gum rate. There was no change under
mist with increasing acacia gum rate. Under mist, percent rooting for 5%, 10%, and 20%
acacia gum was higher under humidity tent
Sky pencil holly cuttings had more positive results under mist than under humidity
tent. Overall, shoot dry weight, root dry weight, root rating, and percent rooting
decreased as acacia gum concentration increased. The acacia gum seemed to have a
negative effect on sky pencil holly. It appeared to be unsuccessful in reducing water loss
and should probably not be used in cutting propagation of Sky Pencil holly. The results
of this study did not support the possibility of acacia gum reducing the need for mist on
46
this species. Testing on different species at different acacia gum rates may have more
encouraging results. Root dry weight, and root rating seemed to increase with increased
cooler time at 0% Acacia gum, so it appears that without Acacia gum, storage in a cooler
prior to sticking might be beneficial to sky pencil holly.
Gardenia
No treatment had any effect on root dry weight or root to shoot ratio of gardenia
cuttings. However, significant main effects for acacia gum concentration and days in
cooler x propagation method interactions for SDW of gardenia cuttings under either mist
or tent. (Table 7) Under humidity tent, SDW decreased linearly by 23% as cooler time
increased. There was a quadratic response under mist with a 44% decrease in SDW with
increasing cooler time. At 0 days in cooler SDW was higher under mist, and at 8 days in
cooler SDW was higher under humidity tent. On days 4 and 12 there was no difference in
SDW between tent and mist. The gardenia cuttings showed an 18% linear decrease in
SDW with increasing acacia gum rate. SDW (Table 7) under tent and mist decreased with
more time in the cooler. Also, SDW decreased as acacia gum rate increased.
The results in Table 8 show that there were significant days in cooler x
propagation method, acacia gum concentration x propagation method, and acacia gum
concentration x days in cooler interactions for root rating of gardenia cuttings under
either mist or humidity tent. Under the tent there was a quadratic response with a 175%
increase in RR with increasing cooler time, with the lowest RR being at 0 days, then
highest at 4 days, then decreasing from there. Under mist there was a 29% linear decrease
in RR with increasing cooler time. On day 0, RR was higher under mist. On day 8 RR
47
was higher under the tent. On days 4 and 12 there was no difference in RR between tent
and mist. There was a 57% linear decrease in RR for gardenia cuttings under tent with
increasing acacia gum rate. Under mist there was a 34% linear decrease in RR of the
cuttings with increasing acacia gum rate. At 0% and 5% acacia gum rate there was no
difference in RR between tent and mist. However, at 10% and 20% RR was higher under
mist than under tent. On days 0, 8, and 12 there was a 53%, 47%, and 68% linear
decrease in RR with increased acacia gum rate, respectively. On day 4 there was no
significant change in RR with increased acacia gum rate. At 0%, 5%, 10% and 20%
acacia gum rate there was a quadratic response with a 41%, 63%, 78%, and 133%
increase in RR with increased storage time, respectively. Starting on day 0, RR for all 4
concentrations of acacia gum was highest on day 4 and decreased on days 8 and 12.
Overall, under both tent and mist RR for gardenia cuttings was highest after 4 days of
storage and decreased from there. Under both tent and mist, RR decreased as acacia gum
rate increased. With all four of the acacia gum concentrations, RR was highest after 4
days of storage.
Table 9 shows that there were significant days in cooler ? propagation method
and days in cooler ? acacia gum concentration interactions on percent rooting of gardenia
cuttings under either mist or humidity tent after storage in a cooler. There was a quadratic
change with a 275% increase in percent rooting under humidity tent with increasing days
in cooler. The lowest percent was on day 0, the highest on day 4, and then decreased from
there. There was a 36% linear decrease in % rooting under mist with increasing days in
cooler. After 0 and 8 days in the cooler, percent rooting under mist was significantly
higher than the tent. However, there was no difference between tent and mist after 4 and
48
12 days of storage. There was no trend in % rooting of cuttings at 0% acacia gum with
increasing days in cooler. For 5%, 10%, and 20% acacia gum rate, there was a quadratic
change with a 77%, 125%, 160% increase with increasing cooler time, respectively. At
all three acacia gum rates, the highest rooting percentage occurred after four days of
storage and then decreased from there. There was a 50%, 64%, and 70% linear decrease
in percent rooting with increasing acacia gum rate after 0, 8, and 12 days in the cooler,
respectively. There was no change in percent rooting on day 4 with increasing acacia
gum rate.
The results for gardenia were variable between mist and humidity tent. This is
possibly due to gardenia?s waxy cuticle which would slow water loss from the leaves
under shade. Shoot dry weight, root rating, and rooting percentage decreased with
increased acacia gum %, therefore acacia gum had a negative effect on gardenia rooting.
It appeared that many of the plants treated with acacia gum rotted and died. Shoot fresh
weight and dry weight decreased as cooler time increased. Root rating increased after 4
days of storage with all four acacia gum concentrations and decreased from there. It is
possible that storing gardenia cuttings for four days before sticking could be beneficial.
Acacia gum generally had a negative impact on cutting propagation. It did not
appear to decrease the loss of water from cutting. Acacia gum is not recommended for
use in propagation of cuttings. However, storage of cuttings prior to sticking had a
positive effect on rooting. Up to four days in cooler improved rooting compared to
controls. Longer durations resulted in a decline in rooting. Also, intermittent mist was
more effective than the humidity tent.
49
The results indicate that acacia gum may aid rooting of Virginia Sweetspire
cuttings at the appropriate concentration. Acacia gum was ineffective overall in
preventing water loss of Sky Pencil holly and gardenia. It had either no effect or a
negative effect on rooting of the cuttings and is not recommended for use on these
species. Acacia gum is not recommended for use in propagation of cuttings without
further testing. However, storage of cuttings for up to 4 days prior to sticking had a
positive effect on rooting.
50
Literature Cited
1. Hartmann, Hudson T., D. Kester, F. Davies, and R. Geneve. 2002. Plant Propagation
Principles and Practices. Prentice Hall. Upper Saddle River. NJ.
2. SAS Institute Inc. 1999-2001. Cary North Carolina. Version 8.2. October 8, 2002.
3. Thevenet, F. 1995. Encapsulation and controlled release of food ingredients. American
Chemical Society. Washington, DC.
4. Vodyanoy, V.J., J.M. Barbaree, B.A. Chin, W.C. Neely, S.T. Pathirana, T.D. Braden.
2001. Use of Acacia gum to isolate and preserve biological material. United States Patent
and Trademark Office. http://patft.uspto.gov/netacgi/nph-
Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrc
hnum.htm&r=1&f=G&l=50&s1=7022514.PN.&OS=PN/7022514&RS=PN/7022514.
(Last accessed April 2006).
5. Whitcomb, C. E., and L. T. Davis Jr. 1970. Antitranspirants ? a better way to root
cuttings? Amer. Nurseryman. 132:100-101.
51
Table 1. Effect of number of days in cooler on root dry weight, shoot dry weight, and
root rating of Virginia Sweetspire (Itea virginica ?Merlot?) cuttings under either
intermittent mist or humidity tent propagation after storage in a cooler at 38F (3.3C)
z
.
Shoot dry weight (g)
Root dry weight (g)
Root rating
y
# Days in
Cooler
Tent Mist Tent Mist Tent Mist
0
0.23
0.42***
x
0.01
0.03***
3.2
4.2***
4
0.21
0.31***
0.02
0.02**
3.4
3.7
8
0.17
0.24**
0.01
0.01
2.6
2.6
12
0.18
0.26***
0.01
0.02
2.7
2.9
Significance
w
L**
L***
NS
L**
L***
L**
z
There were significant propagation method ? days in cooler interactions, P = 0.05.
y
Root Ratings:0= dead, 1 =alive but no roots, 2 = 1-40 roots, 3 = 40-60 short roots, 4 = 50-70
long roots, 5 = 70-100 roots, through 6 = 100-200 roots
x
Comparison of tent and mist in rows using single degree of freedom orthogonal contrasts, P =
0.01(**) or 0.001(***).
w
Non-significant (ns) or significant linear (L) trends at P = 0.01 (**), or 0.001 (***).
52
Table 2. Effect of Acacia gum concentration, number of days in cooler, and propagation
method on percent rooting of Virginia Sweetspire (Itea virginica ?Merlot?) cuttings
under either intermittent mist or humidity tent propagation after storage in a cooler at
38F (3.3C)
z
.
Acacia gum
concentration
% rooting Days in
cooler
% rooting Propagation
method
% rooting
0% (water
control)
49.9 0 43.8 Tent 48.6b
y
5%
65.9 4 48.0 Shade 54.9a
10%
69.4 8 39.6
20%
60.8 12 39.6
Significance
x
Q**
L***
z
Main effects only were significant, P = 0.05.
y
Based on significance of main effect, P = 0.05.
x
Significant linear (L) or quadratic (Q) trends at P = 0.01 (**), or 0.001 (***).
53
Table 3. Effect of Acacia gum concentration on shoot dry weight of Sky Pencil holly
(Ilex crenata ?Sky Pencil?) cuttings under either intermittent mist or humidity tent
propagation after storage in a cooler at 38F (3.3C)
z.
.
Shoot dry weight (g)
Acacia gum
concentration
Tent Mist Days in cooler
0% (water
control)
0.67
0.67
0
0.70
5%
0.63
0.63
4
0.58
10%
0.58
0.58***
y
8
0.64
20%
0.47
0.47***
12
0.62
Significance
x
L***
L*
Significance
L**
z
There were significant propagation method ? acacia gum concentration interactions. Main
effects for days in cooler were significant, P = 0.05.
y
Comparison of tent and mist in rows using single degree of freedom orthogonal contrasts, P =
0.001(***). Non-significant (ns).
x
Significant linear (L) trends at P = 0.05(*), 0.01 (**), or 0.001 (***).
54
Table 4. Effect of Acacia gum concentration and number of days in cooler on root
dry weight of Sky Pencil holly (Ilex crenata ?Sky Pencil?) cuttings under either
intermittent mist or humidity tent propagation after storage in a cooler at 38F (3.3C)
z
.
Root dry weight (g)
# Days in cooler
#
Days
in
cool-
er
Tent
Mist
Acacia
gum
concen
-tration
Tent
Mist
0
4
8
12
Sig
.
y
0
0.06
0.06
0%
water
control
0.08
0.08
0.06
0.06
0.06
0.12
Q*
4
0.04
0.07**
x
5%
0.06
0.07
0.06
0.06
0.09
0.07
NS
8
0.06
0.07
10%
0.03
0.06
0.06
0.06
0.05
0.07
NS
12
0.11
0.08**
20%
0.001
0.07***
0.07
0.07
0.06
0.05
NS
Sig.
L*
NS
Q***
NS
NS
NS
Q*
NS
z
There were significant days in cooler ? propagation method, acacia gum concentration ?
propagation method, and acacia gum concentration ? days in cooler interactions, P = 0.05.
y
Non-significant (ns) or significant linear (L) or quadratic (Q) trends at P = 0.05(*), 0.01 (**), or
0.001 (***).
x
Comparison of tent and mist in rows using single degree of freedom orthogonal contrasts, P =
0.01(**) or 0.001(***).
w
Root ratings: 0 = dead, 1 = no roots, 2 = 1-10 roots, 3 = 10-20 roots, 4 = 20-30 roots, 5 = 30-50
roots, and 6 =50-100 roots
55
Table 5. Effect of Acacia gum concentration and number of days in cooler on root rating of
Sky Pencil holly (Ilex crenata ?Sky Pencil?) cuttings under either intermittent mist or humidity
tent propagation after storage in a cooler at 38F (3.3C)
z
.
Root rating
w
# Days in cooler
# Days
in
cooler
Tent
Mist
Acacia
gum
concen-
tration
Tent
Mist
0
4
8
12
Sig.
0
1.3
4.3***
0%(water
control)
3.7
4.6**
3.5
4.4
3.3
5.5
L***
4
2.2
5.3***
5%
2.0
4.4***
2.9
3.8
2.8
3.3
NS
8
2.0
3.2***
10%
1.2
4.3***
2.7
3.4
2.5
2.3
NS
12
2.3
4.4***
20%
0.5
3.9***
2.1
3.3
1.6
1.9
NS
Sig.
L**
NS
Q**
L*
L**
L**
L***
L***
z
There were significant days in cooler ? propagation method, acacia gum concentration?
propagation method, and acacia gum concentration ? days in cooler interactions, P = 0.05.
y
Non-significant (ns) or significant linear (L) or quadratic (Q) trends at P = 0.05(*), 0.01 (**), or
0.001 (***).
x
Comparison of tent and mist in rows using single degree of freedom orthogonal contrasts, P =
0.01(**) or 0.001(***).
w
Root ratings: : 0 = dead, 1 = no roots, 2 = 1-10 roots, 3 = 10-20 roots, 4 = 20-30 roots, 5 = 30-
50 roots, and 6 =50-100.
56
Table 6. Effect of Acacia gum concentration on percent rooting of Sky Pencil holly
(Ilex crenata ?Sky Pencil?) cuttings under either intermittent mist or humidity tent
propagation after storage in a cooler at 38F (3.3C)
z
.
Acacia gum concentration
Tent
Mist
0% (water control)
68.2
83.3
5%
36.1
84.7***
y
10%
9.7
83.3***
20%
0.0
74.1***
Significance
x
L***
NS
z
There were significant propagation method ? acacia gum concentration interactions, P = 0.05.
y
Comparison of tent and mist in rows using single degree of freedom orthogonal contrasts, P =
0.001(***).
x
Non-significant (ns) or significant linear (L) trend at P = 0.001 (***).
57
Table 7. Effect of Acacia gum and number of days in cooler on shoot dry weight of
Gardenia (Gardenia jasminoides ?Daisy?) cuttings under either intermittent mist or
humidity tent propagation after storage in a cooler at 38F (3.3C)
z
.
Shoot dry weight (g)
# Days in
cooler
Tent Mist Acacia gum
concentration
Tent and
Mist
0
0.66
0.73***
y.
0% (water control)
0.60
4
0.51
0.53
5%
0.57
8
0.50**
0.41
10%
0.53
12
0.51
0.48
20%
0.49
Significance
x
L**
Q***
Significance
L***
z
There were significant main effects for acacia gum concentration and days in cooler ?
propagation method interactions, P = 0.05.
y
Comparison of tent and mist in rows using single degree of freedom orthogonal contrasts, P =
0.01(**) or 0.001(***).
x
Non-significant (ns) or significant linear (L) or quadratic (Q) trends at P = 0.01 (**) or 0.001
(***).
58
Table 8. Effect of Acacia gum concentration and number of days in cooler on root
rating
z
of Gardenia (Gardenia jasminoides ?Daisy?) cuttings under either
intermittent mist or humidity tent propagation after storage in a cooler at 38F (3.3C)
y.
# Days in cooler
#
Days
in
cooler
Tent
Mist
Acacia
gum
concentr
ation
Tent
Mist
0
4
8
12
Sig.
x
0
1.6
3.4***
w
0%
(water
control)
3.5
3.5
3.2
4.5
3.0
3.4
Q**
4
4.4
4.2
5%
3.4
3.0
2.7
4.4
3.0
2.8
Q**
8
2.7**
1.7
10%
2.2
3.1**
2.7
4.8
1.2
1.4
Q***
12
2.0
2.4
20%
1.5
2.3*
1.5
3.5
1.6
1.1
Q**
Sig.
Q***
L***
Sig.
L***
L***
L***
NS
L***
L***
z
Root ratings: 0=dead, 1= no roots, 2=1-5 roots, 3=5-10 roots, 4=10-20 roots, 5=20-30 roots,
6=30-50 roots.
y
There were significant days in cooler ? propagation method, acacia gum concentration ?
propagation method, and acacia gum concentration ? days in cooler interactions, P = 0.05.
x
Non-significant (ns) or significant linear (L) or quadratic (Q) trends at P = 0.01 (**) or 0.001
(***).
w
Comparison of tent and mist in rows using single degree of freedom orthogonal contrasts, P =
0.05(*), 0.01(**) or 0.001(***).
59
Table 9. Effect of Acacia gum concentration, number of days in cooler, and
propagation method on percent rooting of Gardenia (Gardenia jasminoides ?Daisy?)
cuttings under either intermittent mist or humidity tent propagation after storage in a
cooler at 38F (3.3C)
z
Acacia gum concentration
# Days in
cooler
Tent
Mist
0%
(water
control)
5% 10% 20%
Sig.
y
0
22.2
65.3***
x
55.7
47.2
44.5
27.8
L*
4
83.3
84.7
80.6
83.4
100.0
72.2
NS
8
51.4
27.8**
61.1
55.6
19.5
22.2
L***
12
37.5
41.7
63.9
50.0
25.0
19.5
L***
Significance
Q***
L***
NS
Q*
Q**
Q**
z
There were significant days in cooler ? propagation method and days in cooler ? acacia gum
concentration interactions, P = 0.05.
y
Non-significant (ns) or significant linear (L) or quadratic (Q) trends at P = 0.05 (*), 0.01 (**), or
0.001 (***).
x
Comparison of tent and mist in rows using single degree of freedom orthogonal contrasts, P =
0.01(**) or 0.001(***).
60
CHAPTER 4
FINAL DISCUSSION
The purpose of this research was to evaluate the effectiveness of acacia gum in
reducing water loss during storage of bare root nursery crops, and to test the effects of the
acacia gum on post transplant growth of bare root Forsythia x intermedia ?Karl Sax? and
Magnolia stellata ?Merrill? . The objective of the second study was to evaluate the
effectiveness of acacia gum in reducing water loss during storage and rooting of Itea
virginica ?Merlot?, Ilex crenata ?Sky Pencil?, and Gardenia jasminoides ?Daisy? cuttings.
In the bare-root study, acacia gum dips of forsythia at 5% and 10% offered equal or
better growth of plants in the nursery than the traditional treatments of peat and
hydrophilic polymer and the control water treatment. Given the labor required for
handling peat moss and the expense of hydrophilic polymer, acacia gum at the
appropriate root-dip concentration was equal or better than other treatments on forsythia.
Additional testing is necessary before any commercial recommendations can be made to
the nursery industry.
In the propagation study, more cuttings of Virginia Sweetspire rooted at 10% Acacia
gum concentration, followed by 5% and 20%, than cuttings not treated with acacia gum.
These results suggest that acacia gum may aid rooting of Virginia Sweetspire cuttings at
the appropriate concentration. Acacia gum was ineffective overall in reducing water
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loss of Sky Pencil holly and gardenia. It had either no effect or a negative effect on
rooting of the cuttings and is not recommended for use on these species.
In conclusion, the results of this study indicate that acacia gum is not a better
alternative to the current products on the market used in reducing water loss of bare root
plants. It is also not recommended to reduce water loss of cuttings.