Seed Development And Imbibition Characteristics Of Sophora Japonica

The seeds of Sophora japonica seed was used as research material to study the formation of seed hardness during seed development,and to analyze the spatial and phase changes of water in the seed during the process by nuclear magnetic resonance（NMR）.At the same time,the water absorption characteristics of seeds were studied,and the water gap and path of water movement in seed were determined.The main results are as follows:1.During the seed development,the water content of pods and seeds decreased continuously,the pods changed from green to brown and gradually became beaded,and the seeds gradually changed from green to black and smaller.With the continuous development of the palisade layer in the seed coat,the impermeability of the seed coat gradually formed,the seed water absorption became slow,the germination rate gradually slowed down,and the seed hardness gradually formed.2.The results of nuclear magnetic resonance showed that the water content of pericarp increased and then decreased during development,and the pods were connected with seeds by hilum and lens region,and the water content in this region decreased gradually with the development.In the early stage of seed development,the water content in endosperm was higher than that in embryo.With the seed development,the water content in endosperm and seed embryo decreased gradually.Finally the embryo contained a small amount of water,while the endosperm contained almost no water.With the seed development,water in the seed gradually changes from free to bound state,and the final water mainly exists in the form of bound water.3.The seed coat structure of seed is different in seed micropyle,hilum and lens.The seed coat in the seed micropyle and hilum is thicker,and the micropyle is mainly composed of cuticle,palisade layer,osteosclereids and sclerenchyma;the hilum region is mainly composed of counter parenchyma cell,palisade layer,tracheid group,sclerenchyma layer and parenchyma layer;the lens region is the thinnest,which is composed of cuticle,palisade layer and sclerenchyma layer.The palisade layer is the main structure that hinders the water absorption of S.japonica.After the seed lens region opens a crack to the palisade layer,and the seed can absorb water.4.Combined with the results of Vaseline^TM blocking test,TTC staining test and MRI,it can be determined that the lens is the initial water absorption point of S.japonica seeds.5.The application of NMR technology in seed absorption:after entering the seed through the lens the water moves to the end of the cotyledon in the endosperm,and then transports water to the hilum through the vascular bundle.With the activation of the seed coat in hilum region,water is transported to the micropyle,and the seeds enter the stage of rapid water absorption after radicle hydration.The water is transported to the cotyledons through the radicle.When the seed absorbs for 84 h,the micropyle opens gradually and the seed is ready to germinate.In the process of seed water absorption,the change of water phase is opposite to that of development.The water in the mature seed mainly exists as bound water.With the progress of seed absorption,the water changes to a free state.