| Field, greenhouse and growth chamber experiments were conducted in 2001 to 2003 at the Research Center of China Agricultural University to study chemical control on efficient expression of soybean yield and quality with cultivar Keng 5 and Zhonghuang 13. The following aspects were studied in the experiments: The effects of plant growth regulator SHK-6 (mixture of DTA-6 and DPC) on the soybean canopy development, leaf photosynthesis, assimilates transportation, root physiological function, and nitrogen fixation. The main results were:1. SHK-6 improved the expression of yield and quality of the varieties. In high protein soybean, SHK-6 treatments increased seed yields and protein content by 20 to 31% significantly. SHK-6 also improved necessary amino acids and Mean amino acids contents, especially 10% more methionine. In homo soybean, SHK-6 treatment increased seed yields by 2.25 to 11.74%. There were no difference in protein and oleagmous contents. SHK-6 treatments increased the weights of pod and grain, the numbers of pods and grains and biomass.2. Soybeans heights were decreased with increasing SHK-6. Late leaf spraying treatments reduced soybean heights more than the early application. SHK-6 treatments increased the internodes weights. While the internodes weights decreased with increasing soybean densities. In our experiments, the best expression of yield and quality was obtained with 40 plant.m-2, and leaf spraying 100mg.L-1 SHK-6 at V3+RJ stage. SHK-6 treatments increased photosynthetic rates, chlorophyll contents, photochemical efficiencies (FV/FM) and the activities of RuBPCase, PEPCase and SPS at different densities. The physiological activity of roots was improved by SHK-6. It showed: the transporting contents of inorganic ion, NH4-NO3-, and amino acid in saps were greatly increased. The bleeding saps and the root physiological activity were prolonged, and nodule numbers and nitrogen fixation were improved. The contents of CTKs, GAs and 1AA in root and bleeding saps were significant increased, while ABA content was decreased before R5.3. Chemical control can reduce the effect of water deficit stress on the yield and quality. PGRs treatments increased the biomass and the weight of grains (expect 6-BA), pods, roots and nodules (except S3307), decreased bad grains, and increased the content of protein and oleaginous. PGRs treatments significant promoted the translocation of 14C assimilates to the roots, nodule and pods, and enhanced the I4CO2 release rate. Chemical control increased the physiological activity in leaves. It showed: PGRs treatments significantly increased water potential, F,/FM, Chl and Pn compared to the control. The activity of RuBPCase, PEPCase, SPS, SOD and POD was promoted by PGRs treatment, while content of MDA was reduced. PGRs treatments significant increased the content of ABA, GA and CTKs in different parts of soybean under water deficit stress. The content of CTKs and ABA was sharply increased by PGRs treatments, and promoted the accumulation of 1AA and GA in leaves, it was necessary to maintenance the physiological function in leaves under water deficit stress. Moreover,PGRs significantly increased the root activity and nitrogen fixation.4. BR and SHK-6 treatments significantly increased the numbers and weight of nodule, the activities of nitrogen fixation, sucrose synthase (SS), glutamine synthetas (GS), glutamate synthase (GOGAT) and urease. The biomass and the nitrogen content of roots, nodules, and shoots were significant improved by PGRs treatments. Chemical control regulated the hormones to control the ability of nitrogen fixation. It was found that the CTK/GA and CTK/IAA was up-regulation nitrogen fixation activity of nodules, and the IAA/ABA and GA/ABA was down-regulation. In different rhizobium strains, CTKs and 1AA obviously increased the activity of nitrogen fixation and polysaccharide content in rhizobium, and decreased the number of rhizobium. But GA treatment was reversed by CTKs. ABA treatment decreased the activity of ni...
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