Enhancement of Seed Germination and Seedling Growth of Lenten rose
Type of DegreeThesis
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The purpose of these studies was to develop methods to increase germination percentage, shorten germination time, provide more synchronous germination, and result in more efficient seed propagation techniques for Lenten rose (Helleborus × hybridus). Chapter two investigated the number of weeks of warm followed by cold stratification needed for germination. Seeds received warm 25C (77F) durations for 4, 6, 8, or 10 weeks followed by cold 4C (39F) durations for 4, 6, 8, or 10 weeks plus a control. The fewest days to radicle, hypocotyl, and first true leaf emergence generally occurred with shorter durations of warm and cold. Ten weeks of warm duration produced the highest radicle, hypocotyl, and true leaf counts. Four weeks of cold duration produced the highest true leaf count, but results were inconclusive for the effect of cold duration on germination rate, time to germination, and range of germination. Average plant width decreased with increasing cold and warm durations, while plant height decreased with increasing warm durations. Chapter three investigated the effects of density sorting on seed germination and seedling growth in Lenten rose. Treatments consisted of four seed density groups and an unsorted control. The highest radicle, hypocotyl, and first true leaf counts were found in the unsorted control, while the lowest were found in the lowest density. The lowest density was greatly impacted by high disease incidence. In chapter four, seeds of Lenten rose were treated with three GA3 concentrations at 200 ppm, 400 ppm, or 800 ppm with three application times prior to warm stratification, between warm and cold stratification or after cold stratification and a control. Treatment of seeds with 200 ppm, 400 ppm, and 800 ppm GA3 prior to warm stratification increased germination rates by 42% to 58%. The results of Chapter two indicated that a short cold duration might be desirable in producing the highest true leaf counts in Lenten rose; however, the shortest cold duration studied was 4 weeks. Therefore, Chapter five was conducted to further investigate the appropriate weeks of cold stratification for germination of Lenten rose. Treatments consisted of 1, 2, 3, 4 or 5 weeks of cold 4C (39F) durations plus a control. The highest percent radicle emergence and the fewest days to radicle emergence occurred after 1 week cold stratification. The shortest range of radicle emergence occurred after 3 weeks and the longest range after 0 weeks cold stratification. Based on the results with regard to temperature requirements and the ability of GA3 to promote germination, this seed lot of Lenten rose exhibits nondeep, simple morphophysiological dormancy.