| The effects of enhancement of solar ultraviolet-B(UV-B,280~320 nm) radiation caused by ozone depletion and increasing atmospheric CO2 concentration resulting from environment damage on biosphere have already got comprehensive notes among the government and scientists. Plants growing in enhanced UV-B radiation or elevated CO2 concentration may change with their physiological, morphological structure and the process of growth and development directly or indirectly. Although extensive studies were done about biological and ecological effects of single factor of them, little was known about the combined effect of enhanced UV-B and high CO2. In this paper, influences of enhanced UV-B and doubled CO2 on the growth and development and physioecology of broad bean and wheat were investigated with the method of plant physiology and ecology by using OTC outdoor. The result shows:(1) Doubled CO2 decreased the sensitivity of broad bean and wheat to enhanced UV-B radiation. The resistance of wheat to enhanced UV-B is bigger than that of broad bean, exposed to doubled CO2.(2) Broad bean and wheat exposed to both of enhanced UV-B and doubled CO2 grew normally. Enhanced UV-B could lengthen growing and development period, and phonology is delayed. But doubled CO2, which speeded up the growing and development, made development period shorten, and speeded the phonology.(3) The plant heights of broad bean and wheat under treatment of both enhanced UV-B and doubled CO2 were close to that of control. Enhanced UV-B made theheights lowered, and the lowered extent increased with development process. Doubled CO2 made the heights increased, and the increased extent enhanced with development process. Compared with each other, enhanced UV-B affected plant height of wheat more than that of broad bean, and doubled CO2 affected plant height of broad bean more than that of wheat.(4) The combined effects of enhanced UV-B and doubled CO2 didn't change fundamentally the biomass of broad bean and wheat. Their biomass declined under enhanced UV-B, the declined extent varied in different development stages. The biomass under doubled CO2 could increase, the increased extent of aboveground biomass was different from that of underground biomass.(5) The combined effects of enhanced UV-B and doubled CO2 didn't change the yield of broad bean and wheat on the whole. Their yield could also be reduced under enhanced UV-B, and increased under doubled CO2.(6) The yield formation in broad bean and wheat didn't change basically under treatment of both enhanced UV-B and doubled CO2. Filled grain number per plant, grain number and grain weight of broad bean were decreased by enhanced UV-B, but increased by doubled CO2. Total panicle number, total grain number and 1000-grain weight of wheat were decreased by enhanced UV-B, but increased by doubled CO2.(7) The contents of chlorophyll and carotenoid of broad bean and wheat didn't change basically under the combined effects of enhanced UV-B and doubled CO2. They were decreased by enhanced UV-B, but increased by doubled CO2. The increased extent in broad bean was bigger than that in wheat.(8) The combined effect of enhanced UV-B and double CO2 didn't change the photosynthetic rate (Pn) of broad bean and wheat on the whole. Enhanced UV-B decreased Pn, and doubled CO2 enhanced Pn. The change extent declined with developmental process.(9) The stomatal conductance (Gs) of broad bean and wheat could be reduced in any case of each or combined treatment of enhanced UV-B and doubled CO2. The reduced extent of combined stress was the biggest, the effect of CO2 on Gs was less than that of UV-B.(10) The combined effects of enhanced UV-B and doubled CO2 increased WUE greatest. The enhanced UV-B decreased WUE, but doubled CO2 made WUE higher.(11) It was primary response that CO2 was found to be capable to protect plants from UV-B-induced damage by increasing the UV absorbing compounds, carotenoid and soluble protein contents. These were the same under combined treatment, thus plants g...
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