Cytology, Biochemistry And Biological Roles Of Vegetative Storage Proteins In Woody Plants

People always attach importance to the nitrogen metabolosm in plant for nitrogen, a major mineral element, is necessary for plant growth and development. However, we still have little knowledge of the nitrogen storage in vegetative organs although more progress in understanding the nitrogen absorption, assimilation, transportation and the nitrogen storage in seeds have been achieved in recent years.The nitrogen metabolism of woody plants is characterized by storing nitrogen compounds in their vegetative organs. The stored nitrogen compounds play an important role in the tree growth and in the resistance of tree to environmental stress. In addition, the knowledge of nitrogen storage is a basis of developing the cultivation techniques of woods and fruit trees.At the late of 1980s, available evidence indicated that there presented a kind of proteins specific for nitrogen storage in vegetative organs of woody plants, and ,thus, the proteins were defined as vegetative storage proteins.To date, little is known about the cytology, biochemical properties and biological roles of vegetative storage proteins in woody plants. As a result, people have to draw on the experience of seed storage proteins to understand the vegetative storage proteins and always equate their importance with that of seed storage proteins. It is commonly accepted that the nitrogen stored in vegetative organs buffers the nitrogen necessity if current supply of nitrogen is not available for the growth of woody plants. This understand of stored nitrogen compounds restricted seriously the progress in the investigation of vegetative storage proteins.In the dissertation, we studied more extensively the cytology, biochemical properties and biological roles of vegetative storage proteins in Swietenia macrophylla and in Hevea brasiliensis by light- and electron microscopy, SDS-PAGE, PAGE, immuno-blotting, indirect immunohistochemical localization and colloidal gold labelling and cDNA clone techniques. To examine the distribution of vegetative storage proteins in woody plants, we sampled at random 70 tree species of tropical hardwoodsin 64 genera of 18 families and 30 tree species and 1 variety of temperate deciduous hardwoods in 28 genera of 15 families. We further investigated more systematically the distribution, ultrastructure of vegetative storage proteins in Rosaceae (17 species and 3 varieties in 12 genera), Leguminosae (10 species and 1 variety in 9 genera) and Meliaceae (16 species and 2 varieties in 12 genera), identified many vegetative storage proteins and tested their irnmuno-relatedness in Meliaceae and in other families.The protein-storing cells in Swietenia macrophylla were found to be Populus-type, i.e. ordinary parenchyma cells containing both vacuolar protein inclusions and starch grains. The protein inclusions in a granular appearance accumulated in the central vacuole and starch grains generally in the cytoplasm of ordinary parenchyma cells. The storage protein accumulated in large quantity in the vegetative organs of Swietenia macrophylla at the period near leaf fall and in the leaf-fall period with terminal branchlets much richer in the storge protein than trunks and roots. The protein accumulated mainly in secondary phloem parenchyma cells and secondary phloem ray cells. The degradation of storage protein in terminal branchlets of Swietenia macrophylla synchronized with new shoot growth after leaf-absent period, suggesting that the protein was utilized to support the growth of new shoots. When the diminishing of the storage protein below the girdled site was blocked, the new shoot growth was also restrained. The storage protein in the trunks and roots diminished dramatically after the new shoot had fully developed and the protein had disappeared completely when the cambia of these organs activated vigorously. In the annual growth cycle of Swietenia macrophylla, the storage protein accumulated firstly in the new shoot rather than in the other organs. The protein accumulation began one month after the leaves of new...