Enhancement effects of pre-sowing treatments on seed performance of rice (Oryza sativa L.)

The objective of these studies was to evaluate the effectiveness of polyethylene glycol (PEG) osmoconditioning and gibberellin treatments in enhancing seed germination and seedling vigor in two semi-dwarf cultivars of rice, Lemont and Maybelle. For most experiments the seeds were separated into high specific gravity ({dollar}>{dollar}1.18) and low specific gravity ({dollar}<{dollar}1.18) categories. The osmoconditioning (OC) treatment consisted of incubating the seeds on filter paper saturated with aqueous PEG adjusted to {dollar}-{dollar}12.7 bars osmotic potential for 7 days at 18{dollar}spcirc{dollar}C. Gibberellin (GA{dollar}sb3{dollar}) was applied as a seed soak (2 hr), singly or in combination with OC prior to planting.; Final germination percentage under standard test conditions was not significantly affected by OC and GA{dollar}sb3{dollar}. Rate of germination, however, was significantly accelerated by the treatments and there was an interactive effect of treatment and seed specific gravity.; Under stress levels of temperature, both percent and rate of germination were significantly improved by OC. Maximum beneficial effects, however, were obtained when OC and GA{dollar}sb3{dollar} were combined. Within a temperature range from 13{dollar}spcirc{dollar} to 41{dollar}spcirc{dollar}C, OC not only improved the overall rate of germination but also extended the temperature range for germination. Seed performance was also improved by OC under low water potential conditions in terms of both rate and percent.; OC and GA{dollar}sb3{dollar} treatments increased the rate of seedling elongation and the absolute length of seedling components attained in a specific period. GA{dollar}sb3{dollar} had the greatest effect on elongation of the mesocotyl, especially in cultivar Lemont.; Enhanced germination and emergence of osmoconditioned seeds was also observed under field conditions, especially for cultivar Maybelle. Less pronounced effects were observed for Lemont.