Effects Of 1,2,4-three On Physiological Characteristics And Yield Of Rice With Different Tolerance

The experiment was conducted in the experimental farm and pasture of Yangzhou University (32.39 degrees N,119.42 degrees E) during 2013-2015, which using Two cultivars, Ningjing 1 (TCB sensitive) and Yangfujing 8 (TCB tolerant), were planted in soils containing 0 (CK),10,20, 40 and 80 mg TCB per kg soil. In order to explore the responses of different rice cultivars to TCB, and provide the basis for the high, stable, and safe production of rice, we studied the effects of 1,2,4-trichlorobenzene (TCB) at different concentration levels (0,10,20,40, and 80 mg TCB per kg dry soil) on the Effects of root characteristics, physiological characteristics, photosynthetic characteristics, morphological structure and yield structure of the two rice cultivars with different tolerance to TCB. The results showed that:(1) Different concentrations of TCB had significant effects on root morphology of two rice varieties at seedling stage, and the difference was significant. With TCB concentration increasing, the plant height, fresh weight, the chlorophyll content, Root activity, total root length, average root diameter, root number, branch number, root table area, root volume of Ningjing 1 decreased significantly, and the declines of Nangjing 1 was larger than that of yangfujing 8. Root length, root tip number, number of branches and root surface area were more sensitive to TCB treatment. Root diameter was significantly larger than that of control under low concentration TCB treatment. At the medium and high levels, Ningjing 1 was more sensitive than Yangfujing 8.(2) Significant differences were found in the effects of TCB levels on grain yield and photosynthetic parameters of flag leaf between the two cultivars. Plant height, fresh weight, and yield of Yangfujing8 were significantly increased, chlorophyll content, net photosynthetic rate, intercellular CO2 concentration, transpiration rate, and qn were slightly increased, while Fv/Fm and Fv/Fo were slightly decreased at the low TCB concentration (10 mg/kg) level. Under the same condition, the net photosynthetic rate, CO2 intercellular concentration, transpiration rate, ΦPSⅡ, Fv/Fm, Fv/Fo,qp, yield of Ningjing 1 were slightly declined with significant reduction of stomatal conductance. In the low concentration TCB treatment Ningjing 1 stomatal conductance (Gs) a larger decline, with the increase of TCB concentration decreased gradually easing. Effects of TCB on Photosynthes is of Ningjing 1 was mainly caused by stomatal limitation. The ΦPSⅡ, Fv/Fm, Fv/Fo, qp, yield of Ningjing 1 were significantly decreased at the low TCB concentration (20 mg/kg) level and the Fv/Fo were more sensitive than the Fv/Fm. Showed that the electron transfer activity of ΦPSⅡ was significantly inhibited, and the heat dissipation capacity was decreased. While Yangfujing 8 showed its strong tolerance, light protection ability. Our study indicated that the effect of TCB on photosynthetic characteristics and yield of rice was not only related to TCB concentration, but also diverse in cultivars.(3) Significant differences were determined in the effects of TCB levels on the grain yield and physiological characteristics during grain filling period between the two cultivars. With the increase in TCB level, the yield of Ningjing 1 was reduced gradually and the yield of Yangfujing 8 was increased at the two low TCB levels of 10 and 20 mg/kg and significantly decreased at higher TCB levels. At the medium and high TCB levels (40 and 80 mg/kg), the panicle number per pot, grain number per panicle and seed setting rate of Ningjing 1 decreased significantly, with decrements significantly bigger than Yangfujing 8, while there was no significant difference in 1000-grain-weight between TCB treatments. Our study found that the yield structure of the decline in the order was the number of spikes> grain number> seed setting rate. The plant height and dry biomass weight of Ningjing 1 were reduced at higher degrees than those of Yangfujing 8. At the low TCB level (20 mg/kg), chlorophyll content, root activity and soluble protein were significantly decreased in the leaves of Ningjing land slightly increased in the leaves of Yangfujing 8. The activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) of the leaves of two cultivars in leaves were increased at low TCB levels and decreased at high TCB levels. At the low TCB levels of 10 and 20 mg/kg, the activities of antioxidant enzymes in Yangfujing 8 were significantly higher than in Ningjing 1. At the highest level of 80 mg/kg, the activities of antioxidant enzymes were significantly lower as compared with the control, with bigger decrements than those in Yangfujing 8. The content of MDA in leaves of Ningjing 1 increased more remarkably than that in Yangfujing 8, indicating that lipid peroxidation was more serious in Ningjing 1. Our study indicated that low TCB levels slightly promoted rice yield, biomass weight, chlorophyll content, protein content and the activities of antioxidant enzymes of the leaves of Yangfujing 8. TCB at the medium and high levels had more inhibitive effects on Ningjing 1 than on Yangfujing 8. Compared with Ningjing 1, Yangfujing 8 was more resistant and adaptable to TCB at different levels.