旱作春玉米冠层及叶片瞬态气体交换及水分利用效率日变化特征

Diurnal variation of instantaneous gas-exchange over canopy and leaf level of spring corn in arid areas

旱作作物不同尺度瞬态气体交换和水分利用效率同步观测的研究，对于节水高效农业理论研究和生产实践均具有及其重要的意义。该文采用涡度相关技术和LI—COR6400便携式光合作用测定仪测定旱作春玉米灌浆期冠层、叶片瞬时CO2和H2O汽交换速率，并分析其瞬态水分利用效率日变化特征。结果表明，旱作春玉米灌浆期0～100cm根层土壤相对湿度为40％时，日变化过程中晴日中上部位叶片的光合速率高峰值为1．3mg·m^-2·s^-1（29．82μmol·m^-2·s^-1），与同纬度地区灌溉玉米的光合速率高峰值相近；而群体下光合速率高峰值为0．9mg·m^-2·s^-1（20．65μmol·m^-2·s^-1），只及同纬度地区灌溉玉米灌浆期光合速率高峰值的54．5％；群体和叶片水分利用效率高峰值分别为0．16g（CO2）／g（H2O）和0．06g（CO2）／g（H2O），正午前后分别维持在0．0055-0．0123g（CO2）／g（H2O）和0．0113～0．0197g（CO2）／g（H2O），叶片尺度的光合速率和水分利用效率在10：00以后的时段内明显高于群体水平。

Information on the relationship between crop photosynthetic rate and water use efficiency at the leaf level and these at the canopy level is important on the study of theory and practice of high efficiency and watersaving agriculture. The authors simultaneous made instantaneous CO2 and H2O exchange rate, and instantaneous water use efficiency measurement at both leaf and canopy levels in a rain-fed cropping system with spring corn during filling stage by Li-6400 infrared gas analysis meter and eddy correlation system. The results showed that in arid areas water stress was the main factor influencing the net photosynthesis rate and water use efficiency. In the diurnal course, when soil relative moisture was about 40% at 0-100 cm soil layer, the maximum of net photosynthetic rate at leaf level occurred at about 10 ： 00 under soil water stress, and at about 12 ： 00 at canopy level on sunny days, the maximum leaf photosynthetic rate reached 1.3 mg. m^-2 . s^-1, almost close to those of irrigation corn at similar latitude area, and the maximum canopy assimilation rate were 0. 9 mg. m^- 2 . s^-1, reached 54.5% of those of irrigation corn at similar latitude area during filling stage, respectivelyl; The maximum values of instantaneous water use efficiency at leaf and canopy level were 0. 16 g（CO2）/g（H2O） and 0.06 g （CO2）/g（H2O）, and ranged between 0. 0055 g（CO2）/g（H2O） and 0. 0123 g（CO2）/g（H2O）, 0. 0113 g（CO2）/g （H2O） and 0. 0197 g（CO2）/g（H2O） around noon, respectively. Instantaneous net photosynthetic rate and water use efficiency at leaf level were higher than those at canopy level after 10 ： 00.