The Photosynthetic Character And Its Responds To Drought In Mulberry-soybean Intercropping System

Along with population increases and the crop acreage decreases, agroforestry get more and more attention in the agricultural production. Agroforestry is a land system that use in controlling woody plants artificially with crops and livestock farming combined in many parts in a land, which have a high production and effective use of land resources, preventing plant diseases and pests, controlling weed in the field. Mulberry is planted in a large area in Heilongjiang province, and plays a important role in revegetation of vulnerable ecological region and agroforesty development. Agroforesy in mulberry and soybean intercropping, for example, mulberry with branches, mulberry without branches, own-root mulberry and grafts mulberry with soybean intercropping, have been utilized in many areas in Heilongjiang province. A huge mass of data on plant physiology of cultivation in mulberry has been accumulated. However, the research on interspecific effects in mulberry and soybean intercropping system and its respondes to drought is lack of data, especially, few studies have described photosynthetic characteristics in mulberry and soybean intercropping. In this paper, taking mulberry-soybean intercropping system as object, photosynthetic characteristics in mulberry and soybean intercropping and its responses to drought and nitrogen supply were investigated to find out the interspecific facilitation of plant biodiversity in agricultural production of mulberry and soybean intercropping and the effects in increasing the drought resistance to describle agroforesty structure and function.The result showed that intercropping of mulberry and soybean promoted the photosynthesis of mulberry, but soybean photosynthesis had no changes, the interspecific facilitation was more important than that of interspecific competition. Photosynethetic rate, Transpiration rate, stomata conductance andmaximal photochemical efficiency in leaves of intercropping mulberry were higher than that of the monoculture mulberry, and interspecific facilitation was significant. The chloro, superoxide dismutase, catalase, solube portein content and malondialdehyde in leaves of intercropping mulberry under water deficit or drought were higher than that of the monoculture mulberry, intercropping the adaptability to drought was improved obviously compared to monoculture, and the intercropping was conducive to improve quality of mulberry leaf. Drought inhibited the nodule formation and nitrogen fixation of soybean, increasing nitrogen to intercropping of mulberry and soybean improved resistance to light droght and moderate drought of intercropping system, but increasing nitrogen was not obvious under heavy drought.The conclusion from results was that interspecific competition and interspecific facilitation coexisted in mulberry and soybean intercropping system. And we found that mulberry-soybean intercropping system not only promote the drought resistance through interspecific facilitation, but also regulate the drought resistance through notrigen, which it was very important in optimizing and regulation the agroforestry. Research results in this paper, was helpful or useful to understand deeply system stability of ecological construction and function, and to use natural resources. At same time, this results provided theoretic surport to estibilish stabily and efficient agroforesty, and provide scientific basis for species choice and arragement in agroforesty.