Coat Structure and Regulation of Dormancy in Sinapis arvensis L. Seeds

Abstract

Summary Charlock, or wild mustard (Sinapis arvensis L.), is an annual weed that grows in winter cereal crops in Europe. Frequently, drought conditions affect the growth of the mother plant, and the seeds show a remarkable morphological heterogeneity in weight, size and colour at the moment of dispersal. Under a wide range of environmental conditions (water, temperature, oxygen and light), the percentage of germination is always lower than five per cent. Exogenous gibberellic acid applications (>_ 750 /M GA3) break dormancy and also reveal a physiological heterogeneity in the seeds. Independently of the GA3 concentration used, germination of red seeds (the smaller ones) is always higher than that of black seeds. Histological studies show that the seed coat structure (epidermis, macrosclereid cells, pigmented cells and aleurone-like cells) does not differ significantly (p >0.05) between the two types of seeds. Excised embryos of red and black seeds germinate and develop perfect seedlings even after five years of dry storage (RH :S 20% and T = SoC). Abscisic acid analysis by GC-MS has shown the presence of similar amounts in the two types of seed. This leads to the following hypothesis: Red and black seeds have the same level of inhibitors, but red seeds can leak their inhibitor more rapidly. This is supported by the fact of similar levels of abscisic acid in red and black seeds at maturity. Similar quantities of GA3 absorbed by the two types of seeds is also in favour of the same hypothesis.