Abstract: SEM observation shows that, the micropyle in mature seed is closed, hilum possesses hilar groove under which there is reticular tracheidal bar, which function as for water-storage and permeation. From out inwards the seedcoat includes four layers viz cuticle, palisade, osteosclereid and parenchymatous layer The structure of hilum and/or seedcoat was damaged by treating the seed with various kinds of organic solvents and concentrated sulfuric acid in different durations or by mechamcal methods. It was found that surface layer and hilum were erosion-nonresistant; the palisades had thick cell walls and were orderly arranged, and contain phenols. They are the main barrier controlling the entrance of water through seedcoat. Erosion with concentrated sulfuric acid and mechanical damage of seedcoat are effective methods for overcoming its impermeability and raising germination capacity of seeds. The factors effecting permeability of seeds and their control mechanism as well as the nature of “light line” of palisades were discussed.

Key words: sesbania cannabina, Structure of seedcoat, permeability