Variation in degree of intermediate complex morphophysiological dormancy in seeds of Bunium persicum (Apiaceae)

Abstract

Bunium persicum is an important medicinal plant, but the requirements for seed dormancy break and germination are not well known. Based on available information, we hypothesized that seeds have an underdeveloped embryo and physiological dormancy (PD), and hence morphophysiological dormancy (MPD), and that populations of this species may have different degrees of MPD which demand different germination requirements. In this study, we evaluated embryo growth in seeds from four B. persicum populations at different temperatures and tested germination at varying constant temperatures, with or without GA3 and cold stratification. Seeds from the four populations had a fully differentiated, small, linear but underdeveloped embryo. The initial embryo‐to‐seed length ratio was 0.14–0.17, but it increased to 0.71–0.75 before germination at 5°C. Little embryo growth occurred at 15°C and no growth occurred at 25°C. GA3 effectively increased germination percentages, replaced cold stratification, reduced the required period for cold stratification, and in combination with cold stratification increased the maximum temperature of germination. Therefore, seeds from the four populations have intermediate complex MPD. Additionally, the germination responses of seeds from the four populations to GA3, cold stratification, or both were different, suggesting variation in the degree of PD. Bunium persicum seeds developed in cool and wet conditions were more dormant than those developed under warm and dry conditions. Thus, we showed that different climates can affect the depth of PD in a species whose seeds have MPD, resulting in variation in the degree of intermediate complex MPD at the population level.