Effects Of Selenium On Alleviating Membrane Lipid Peroxidation Of Soybean Under Continuous Cropping Stress

Soybean is one of the dominant crops in Heilongjiang Province, but continuous cropping stress degrades soybean quanlity and decreases the yield, which have been the prominent problems in practice. Field experiment, pot experiment and seedling experiment were conducted to study the effects of selenium on alleviating membrane lipid peroxidation of soybean under continuous cropping stress and provide the theoretical basis for resistant fertilization. By determining the giutathione peroxides(GSH-Px) activity in soybean leaves, malonaldehyde(MDA) content, chlorophyll content, and DNA content in soybean leaves, as well as the content of phosphorus (PX potassium (K).. magnesium (Mg).. sulfur (5).. boron (B) and zinc (Zn) in soybean aerial part, measuring the dry matter weight and yield, and observing the ultra structure of soybean leaf and nascent root by transmission electron microscope, we draw the conclusions as following: Field experiment and pot experiment showed that compared with alternative cropping, continuous cropping decreased the GSH-Px activity in soybean leaves, increased the MDA (the product of membrane lipid peroxidation) content. The ultra structure of the chloroplast in soybean leaves and mitochondrion in nascent root were damaged seriously and the chlorophyll content in leaves decreased for continuous cropping stress, and the content of P~. K.. Mg.. S B and Zn in soybean aerial part dropped, too. All these lowered the dry matter weight and yield. Under the same continuous cropping stress, appropriate amount of selenium addition increased the GSH-Px activity significantly, which can eliminate the excessive free radicals effectively caused by continuous cropping stress in soybean leaves, and alleviate the membrane lipid peroxidation. The content of MIDA decreased because the Se-treated soybean had enough selenium to consume. With appropriate amount of selenium addition the ultra structure of chloroplast and mitochondrion in nascent root were kept well though the soybean were grown under continuous cropping stress. The chlorophyll content improved. The content of P.K.Mg.S.B and Zn in soybean aerial part were all increased, so did the dry matter weight and yield. In addition to these, seedling experiment even stated that adding appropriate amount of Se to Se-deficient soil can enhance the DNA content in soybean leaves . Correlation analysis was made by using 12 series data selected at random, and the result showed that GSH-Px activities kept significant positive correlation with DNA content and MDA content kept remarkable negative correlation with DNA content respectively in the range of selenium 2 concenthetion used in the experiment.Postgradtale: Lei SunMajor: Plant NutritionSupervisor: Professor Yuanying Liu...