非洲鳳仙花、黃帝菊、百日草種子浸泡矮化劑Paclobutrazol、Uniconazole對其發芽及穴盤苗品質的影響

Abstract

Height control is particularly important to produce the high quality seedlings of bedding plants in Taiwan, where environmental control is more costly for regulating plant height. Retardant application as spray is used commonly in commercial practice but non-uniform plant size can result from non-uniform application. The objectives of the thesis were to compare germination performance, seedling growth for three bedding plant species (impatiens, melampodium, zinnia) after soaking seeds in paclobutrazol or uniconazole. Paclobutrazol at 250 to 200 mg•L-1 did not affect the germination percentage of impatiens while uniconazole treatment at 15, 30 mg•L-1 reduced the germination percentage for 95.2 and 92.5%. Seeds of melampodium presoaked with uniconazole at 15, 30 mg•L-1 for 12 hours would strongly affect seed germination, increasing paclobutrazol from 250 to 2000 mg•L-1 had no significant effect on final germination percentage, T0, T50, T90 and T90-T10 though germination percentage decreased slightly at higher concentration (1000 and 2000 mg•L-1). The effect of uniconazole on zinnia seeds was not significant in T0 and T50, yet it did have increased T90 for 2.3 days at higher concentration (20 mg•L-1). Soaking seeds of impatiens in 5 or 15 mg•L-1 uniconazole for 12 hours rather than 4 hours decreased germination percentage and increased T0, T50 and T90. Seeds of impatiens presoaked with uniconazole for 4 hours at different timescale during imbibition process on germination performance of impatiens ‘Accent Coral’. Germination percentage and T90-10 were not affected by the treatment while the T90 significantly increased by 1~1.3 days. Increasing uniconazole volume during 12-h soak had no effect on total germination percentage, although T0, T50 and T90 increased. Seeds of ‘Accent Coral’ impatiens were soaked for 12 hours with various paclobutrazol or uniconazole. Seeds of ‘Derby’ melampodium and ‘Profusion White’ zinnia were soaked for 8 hours with various paclobutrazol or uniconazole. After the seed treatment, seeds were dried for 24 hours prior to sowing in 288plug tray. For the three species, plants were smaller the higher the concentration of the triazole-type retardant, and the efficacy of uniconazole at lower concentration was greater than that of paclobutrazol at higher concentration. At 11 weeks after sowing, excessive dwarfing occurred in impatiens that received from 15 to 10 mg•L-1 uniconazole. The single- spray of paclobutrazol compared the effect of seed treatment with paclobutrazol or uniconazole on growth of 288plugs impatiens ‘Accent Coral’. Soaking seeds with 5 mg•L-1 uniconazole or 250 mg•L-1 paclobutrazol resulted in 69% or 55% shorter seedling height, respectively, than those of nontreated plants at 5 weeks after sowing. Shoot application 5 mg•L-1 paclobutrazol reduced plant height by 35%. Soaking impatiens seeds with 250 mg•L-1 paclobutrazol or 5 mg•L-1 uniconazole resulted in plant height reduction by 8% and 22% 11 weeks after sowing, respectively. These results indicate that retardants application to seeds may reasonably using a 12 hour soak in 250 mg•L-1 paclobutrazol or 5 mg•L-1 uniconazole for impatiens, 8 hour soak in 250 mg•L-1 paclobutrazol or 5 mg•L-1 uniconazole for melampodium and 8 hour soak in 20 mg•L-1 uniconazole for zinnia.