氮对UV-B辐射增强条件下大麦孕穗期叶片生理特性的影响

通过大田试验,研究在UV-B辐射增强条件下,不同施氮量对大麦孕穗期叶片净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、叶片水分利用效率(WUE)及胞间CO2浓度(Ci)日变化的影响。UV-B辐射设两个水平,即对照(CK,自然光,辐射强度1.5kJ.m-2.h-1)和增强20%(1.8kJ.m-2.h-1);施氮量设两个水平,即低氮和高氮(30kg.hm-2和150kg.hm-2)。结果表明,UV-B辐射增强下,高氮处理的Pn、Tr、Gs和WUE的日平均值比对照分别下降了44.6%、21.8%、17.8%和28.4%;低氮处理分别下降了49.5%、11.8%、12.9%和42.7%,说明UV-B辐射增强可降低大麦叶片的光合作用和水分利用效率,而增施氮肥可缓解UV-B辐射增强对光合作用的影响,并缓解UV-B辐射增强对大麦净光合速率的抑制,但是并不能缓解UV-B辐射增强对蒸腾速率及气孔导度的抑制。Ci及Pn的日变化趋势表明,UV-B辐射增强及氮肥对大麦叶片光合作用的影响不是通过气孔,而是通过对光合作用反应过程的直接影响来实现的。

Effects of Nitrogen Fertilization on Physiological Characteristics of Barley Leaves at Booting Stage under Enhanced UV -B Radiation

Field experiment was conducted to investigate the effects of nitrogen （N） supply on diurnal physiological characteristics in barley leaves at booting stage under enhanced UV - B radiation. The experiment was designed with two UV - B radiation levels, i.e. ambient （CK, 1.5kJ- m-2 h -1 ） and enhanced by 20% （ 1.8kJ m-2 h-1 ）, and two N supply levels, i.e. 30kg-ha-1 （low） and 150kg ha-1（high）, and performed at the station of agricultural mete- orology, Nanjing University of Information Science and Technology. The results showed that, enhanced UV - B radia- tion decreased net photosynthetic rate （Pn）, transpiration rate （Tr）, stomatal conductivity （Gs） and water use effi- ciency （WUE） by 44.6% , 21.8% , 17.8% and 28.4% under high N 1 11.8% , 12.9% and 42.7% under low nitrogen level, respectively. The diation depressed photosynthesis and water use efficiency in harley leaves, evel, res findings pectively, and reduced by 49.5% , suggested that enhanced UV - B ra- increasing N supply could alleviate the dam- age to net photosynthetic rate from enhanced UV -B radiation, but not to transpiration rate and stomatal conductivity. Based on the diurnal change of intercellular CO2 concentration in relation to net photosynthetic rate, it indicates that N supply and enhanced UV - B radiation impacted photosynthesis directly by the process of photosynthetic reaction, not by stomatal conductivity in barley leaves at booting stage.