Effects Of Enhanced O₃and UV-B Radiation On Growth And Yield Formation Of Soybean And Its Photosynthetic Mechanism Of Injury

During the last several decades, significant reductions in the concentrations of stratospheric ozone (O3) have been reported. This reduced ozone concentration causes an increment in ultraviolet-B radiation approaching to the surface earth. The elevated UV-B radiation and increased tropospheric O3concentrations maybe occur together and cause reductions in physiological and biochemical characteristics of crops and economic plants. The effects of UV-B and O3on plant growth and productivity have been reported separately for a large number of species by filed experiment, but only few experiments have focused on their interaction, it is not clear whether UV-B and O3induced damages are brought about with similar mechanisms. In this paper, the responses of photosynthetic system, physiological features, growth and yield under elevated surface ozone and UV-B radiation in field experiment by open top chamber (OTC) had been presented comprehensivly.This will contrbute to the agricultural production and sustainable development. The results in the paper are as follows:(1) UV-B and O3stress adverse effects on soybean growth and physiological, shorten the growth period, decreased leaf area and plant aging. With increasing O3concentration, the soybean plant height, leaf area, nodule number, nodule weight, wet and dry weight growth indices were significantly reduced. On the high O3concentrations the case of enhanced UV-B radiation had no influence, and10%higher UV-B radiation affect the soybean plant height, leaf area and dry weight significantly on low O3concentrations.(2) Enhanced O3concentration and UV-B radiation will lead to the decline in soybean production. The higher O3concentration, the more serious production reduces of soybean, and the effect of O3stress on soybean yield is higher than the UV-B radiation.(3)100nL·L-1enhanced ozone,10%higher than control group UV-B radiation, separately and in combination, ozone caused significant decrease in chlorophyll content, but supplemental UV-B radiation had no impressive effect on it. Compared with UV-B and O3alone, UV-B and O3in combination enhanced the negative effects on soybean chlorophyll content, and ozone stress dominated the combination stress effect of O3and UV-B.(4) The net photosynthetic rate, treatment groups are significant different to control group, but no significant difference between the two single factors treated with the compound, deepened the impact of the combined treatment, but less than the simple accumulation of two separate impacts. The main reasons for decline of soybean leaf photosynthesis are non-stomatal factors. There are some differences of soybean photosynthetic process in response to UV-B and O3stress, more sensitive to O3.