UV-B增加对玉米光合作用日变化的影响

为了探讨地表紫外辐射增强对干旱、半干旱地区农作物生理及生态系统的影响,在宁夏永宁县进行了UV-B增加对玉米光合作用影响的试验研究.试验设置了自然光照组(CK)、R1组(增加0.5W/m 2强度的UV-B)和R2组(增加1.0W/m 2强度的UV-B)3种UV-B照射强度,从玉米三叶期开始每天9:00-17:00照射8h;于2004年5月19日7:00-20:00时,用便携式光合作用测定系统测定玉米叶片净光合速率、蒸腾速率、气孔导度、光合有效辐射、细胞间隙和环境CO2浓度等若干植物生理因子的日变化,并计算了玉米的水分利用效率.结果表明:R1组处理的玉米净光合速率、蒸腾速率、气孔导度和水分利用效率比对照分别下降了57.1%、15.6%、11.0%和49.3%;R2组处理下降了67.5%、18.8%、24.8%和60.6%;地表紫外辐射的增强,对干旱、半干旱地区玉米叶片的净光合速率、蒸腾速率、水分利用效率均随着UV-B的增强而下降,紫外辐射的增强将使该地区玉米产量降低,水资源需求加大.

Effects on enhanced ultraviolet-B (UV-B) radiation on diurnal variations of photosynthesis in corn in Ningxia

As thinning of atmospheric ozone layer,intensities of ultraviolet-B(UV-B) radiation on the surface increasing,these have impacted widely to creature and crops.To approach the impacts of the physiology and ecosystem of crops in the arid and semiarid region,experiments were carried out in Yongning county of Ningxia in 2004,which were about the impacts of enhanced UV-B on diurnal variations of photosynthesis in corn.In the experiments,3 treatment groups(the control group,R1 dose0.5 W/m2 UV-B,R2 dose 0.5 W/m2 UV-B) were set up.From trefoil stage of corn,corn was exposed for 8 hours everyday from 9: 00 to 17: 00.Using a portable CIRAS I photosynthetic analysis system,the diurnal variations of photosynthetic rate,transpiration rate,stoma conductivity of corn leaf were recorded at 7: 00-20: 00 on the 19th of May,and water use efficiency(WUE) was computed.Results showed that,compared to the control group the photosynthetic rate,transpiration rate,stoma conductivity and water use efficiency reduced by 57.1%,15.6%,11.0% and 49.3%,respectively,in plants subjected to R1 dose UV-B radiation(0.5 W/m2) and by 67.5%,18.8%,24.8% and 60.6% in plants subjected to R2 dose UV-B radiation(1.0 W/m2),enhanced UV-B has impacted clearly to the corn in the arid and semiarid region.Photosynthesis and WUE of corn leaf reduced with enhanced UV-B radiation.Enhanced UV-B would reduce corn output and increase water resources.In the background of the global warming and surface UV-B enhanced,cultivation and renew of crop variety and amplification of adaptability and resistivity to environmental condition are important measures to sustain development of agriculture and socioeconomy.