Influences of reduced UV-B radiation on growth and endogenesis hormone contents of rice （Oryza sativa L.）under field conditions

The effects of artificially simulated UV-B radiation reduction under field conditions at Qianyanzhou region of Ji angxi Province on the growth and the contents of chlorophyll and endogenesis hor mones,indoleacetic acid （IAA）,abscisic acid （ABA）,gibberellinA₃（GA₃）and zeatin（Z）,of rice variety ‘Xieyou 432’were studied.The results indicate that the UV-B radiation reduction induces the contents of chlorophyll change significantly,but no difference among the ambient control and treatments of UV-A and UV-A+UV-B is observed.The contents of IAA,GA₃ and Z with the UV-A+UV-B treatment are significantly lower than those of ambient control，decreasing by 40.42%，48.60%，36.21%，respectively .Compared with the UV-A treatment the contents of IAA,GA₃ and Z in the UV-A+UV-B treatment are decreased by 36.52%,70.94% and 54.54%, respectively.The ABA content of UV-A+UV-B treatment decreases by 29.74% compared with that of the ambient control,and by 5.19% compared with the UV-A treat ment.The results also indicate that reduced UV-B radiation has change d the contents of the four endogenesis hormones of the investigated rice cultivar,and accordingly may have adverse effects on the process of growth and development of rice.