Studies On The Vegetative Storage Proteins In The Seedling Of Swietenia Macrophylla

By using enzymatic ethod, light microscopy, SDS-PAGE and Western-blotting, the flowing aspecets were studied: (1) the storage proteins in vegetative organ of the seedling of Swietenia macrophylla, tropical deciduous tree species; (2) relationships between the seed storage proteins and the growth and development; (3) seedling anatomical properties; (4)the changes of nitrate reductase activities (NRA) in leaves during seedlinggrowth and development.The seed of Swietenia macrophylla had no endosperm and contained about 13% proteins on the basis of the dry weight. The major composition of the proteins was storage proteins which were accumulated in cotyledon cells. The proteins could be divided into three groups based on SDS-PAGE. With the germination of seed and the growth of seedling, these three groups storage proteins disappeared gradually and they were consumed completely when seedling leaves matured. Seed-removing seriously hindered the seedling growth and development, indicating that the storage materials, including the storage proteins in seeds, were indispensable to seedling. The effect of seed-removing on seedling seemed to be related to timing of seed-removing , the earlier, the serious.In the transverse section of stem tip, cells were round. They differentiated primary meristem including protoderm, ground meristem, procambium, which weregrown into epidermis, cortex and and vascular cylinder respectively. The cotex had a large proportion of the whole primary structure of the root and there were four xylem ridges, that is to say, tetrarch. The structure of petiole was similar to that of stem and possessed cambium. The young leaves had two vascular bundles in big veins and differentiated mesophyll. The mesophyll had fully cevelopment in matured leaves.The leaves of the seedling of Swietenia macrophylla were the major sites for nitrate assimilation. Under non-induced condition, in vivo assay was applied to determinate nitrate reductase activity(NRA) in the seedling leaves. The results showed that the NRA was high in the leaves and that the NRA was effected obviously by development, fertilization and seed-removing.The NRA could be detected in the leaves of the young seedling in condition of non-fertilization. With the development of the leaves, the NRA was increased gradually. NRA reached to 0.154mol.h-1.g-1 f.wt-1 when leaves matured and therefore dncreased gradually Fertilize application increased NRA markedly and the highest level reached to 0.403 umol.h-1.g-1 f.wt-1 soon after treatment, then began to decrease. In the leaves of young seedling whose seeds was cut off, NRA inceased dramaticaly, the earilier the seeds were cut off, the more obvious the ffecte on the NRA.The main components of the vegetative storage proteins(VSPs) in seedling of Swietenia macrophylla were two proteins with molecular weight of 18 kDa and 21 kDa. In micrtome sections stained with mecury-bromophenol blue, the VSPs, in granular appearance, sequestered in the large central vocuoles of parenchyma cells.Seedling began to accumulate VSPs very early. As soon as leaves matured the 18kDa and 21kDa VSPs could be detected in its young stem by the SDS-PAGE and Western-blotting. Two weeks later the VSPs increased obviously. By using light microscopy, the VSPs were detected in the large central vacuoles of phloem ray and axial parenchyma cells, parenchyma cells, secondary xylem, cortex and pith. But no VSPs granules were observed in cambium cells. Fertilization application couldincrease the level of VSPs, but had no effect on the time the VSPs began to accumulate.Seedling began to sprout soon after the leaf maturited. Whether offering fertilizer or not, the VSPs accumulated in the stem were mobilized during the development of seedling. With the rapidly sprouting of the new shoot, the VSPs in the stem below the new shoot disappeared instantaneously. After new shoot leaves matured, abundant VSPs occurred again in both the new shoot and the stem below it.When the seedling were two-year-old, there were st...