Abstract:

In order to explore the influencing factors on the formation of snap bean hard seed and the methods of hard seed breaking, and to lay the foundation for the research on the breaking hard seeds of snap bean. The seed coat composition, structure and enzyme activity were measured, and germination indexes were determined by alternating wet and dry and mechanical treatments, using the snap bean seeds ‘Shengguan’as test material. The composition of snap bean seeds coat (except for proanthocyanidins) had a significant effect on seed hardness. Compared with non-hard seeds, hard seeds had thicker seed coats in all cell layers, lower protease activities and higher peroxidase and polyphenol oxidase activities in seeds and seed coats. The germination indexes of hard seeds showed an increasing trend with the increase of the number of dry-wet alternation. The germination potential, vigor index and germination index were 21, 9 and 8 times higher than those of the control group when the seeds were treated with alternating wet and dry for three times, respectively. The germination rate, germination potential, vigor index and germination index of mechanically treated hard seeds were 1.07 times, 3.4 times, 4 times and 3 times of those of non-hard seeds, respectively. The hardness of snap bean seeds was affected by seed coat composition, seed coat structure and enzyme activity; alternating wet and dry treatments for three times and mechanical treatments had significant positive effects on seed germination and breaking hard seeds from snap bean seeds.

Key words: snap bean, hard seed, hard seed breaking, seed coat component, firmness