A comparison study of permeable and impermeable and impermeable seed coats of legume seed crops reveals the permeability related structure difference

Impermeability of Legume seeds is commonly related to physical dormancy, which is useful for seed preservation but problematical for the soybean food industry. The primary aim of this study was tocharacterize the structure difference between permeable and impermeable seed coats, revealing the water-controlling structures and demonstrating the water uptake process. Three measurements of water uptake for four Legume species were carried out. The general anatomy of micropyle and seed coat were observed by scanning electron microscopy (SEM). Dye tracking was carried out to investigate the pathway of water movement during imbibition. The mature seed coat of four species contained three layers of cells. SEM observations revealed that the impermeable coat differs from the permeable one. Layer thickness has no direct relationship to the permeability of Legume seeds. The micropyle opening could be observed in permeable seed coats. Osteosclereids could impede the uptake of water; the layer of the osteosclereid near the embryo is hydrophilic and distal sideis hydrophobic. The present research provided a variety of information related to the permeability of Legume seeds. The coat structures of permeable and impermeable micropyles are different in several aspects. A novel finding is that the outer surface of the osteosclereid layer is essential to permeability. (author)