Response of four Vicia species seed germination to water stress

This study investigated seed germination characteristics of four Vicia species from Tibet Plateau under different water potential. The results were summarized in terms of the hydrotime model as following: 1)The base water potential increased as the subpopulation(g) increasing, indicated that the base water potential varied with individual in a seed population; 2) Except Vicia unijuga, the slope of regression line of germination rate and water potential decreased as the subpopulation increased, implied that the hydrotime was not constant in some cases; 3) Compared to other species, V.sativa attained the lowest base water potential, it showed that this species can germinate in the relative drier condition; V.amoena attained the highest b with the lowest hydrotime constant(H), implied that this species will not germinate in the drought condition, but a rapid seed germination may be expected in the favorable water condition; 4) The germination process could be well described by hydrotime model when the water potential was high, however the accuracy significantly decreased when subjected to low water potential approaching to seed germination.