半干旱区膜上覆土穴播对春小麦旗叶光合作用和水分利用的影响

Photosynthetic gas exchange and water utilization of flag leaf of spring wheat with bunch sowing and field plastic mulching below soil on semi-arid rain-fed area

在甘肃定西大田定位试验的基础上,2012—2013年连续2年比较了全膜覆土穴播（PMS）、覆膜穴播（PM）和露地穴播（CK）春小麦旗叶的SPAD值、叶绿素荧光参数、光合气体交换参数以及叶面积指数（LAI）、产量、耗水量和水分利用效率.结果表明：PMS提高了小麦旗叶SPAD值,扬花后显著高于PM,增加了10.0%~21.5%,较CK增加了3.2%~21.6%.PMS的旗叶最大光化学效率（F_v/F_m）、PSⅡ实际光化学效率（Φ_（PSⅡ））和光化学猝灭系数高于PM和CK,较PM最高分别提高了6.1%、9.6%和30.9%,并在灌浆期达到显著差异;而PMS的非光化学猝灭系数（q_N）值最低,并在抽穗期与PM达显著差异水平,2012和2013年分别降低了23.8%和15.4%.PMS的气孔导度（g_s）较PM和CK高,在灌浆期与PM达到显著差异,2012和2013年分别提高了17.1%和21.1%;PMS的蒸腾速率（Tr）较PM提高了5.4%~16.7%,光合速率（P_n）增加了11.2%~23.7%,旗叶瞬时水分利用效率（WUE_i）提高了5.6%~7.2%（除2013年抽穗期外）,并在2012年扬花期达到显著差异.PMS的LAI高于PM和CK,尤其在季节性干旱的2013年达到显著差异.因此,PMS提高了叶片SPAD值,增强了旗叶对光合能量的同化能力和气体交换强度,使更多的光合能量进入光化学同化方向,降低了热耗散,使P_n增加,提高了旗叶WUEi,基于较高的光合速率和群体LAI,最终提高小麦产量和水分利用效率.

Based on the field experiment which was conducted in Dingxi County of Gansu Province, and involved in the three treatments： （1） plastic mulching on entire land with soil coverage and bunching （PMS） , （2） plastic mulching on entire land and bunching （PM） , and （3） direct bunc- hing without mulching （CK）. The parameters of SPAD values, chlorophyll fluorescence parame- ters, photosynthetic gas exchange parameters, as well as leaf area index （ LAI）, yield, evapotrans- piration, and water use efficiency in flag leaves of spring wheat were recorded and analyzed from 2012 to 2013 continuously. The results showed that SPAD values of wheat flag leaves increased in PMS by 10.0%-21.5% and 3.2%-21.6% compared to PM and CK in post-flowering stage, respec- tively. The maximum photochemical efficiency （Fv/Fm） , actual photochemical efficiency （φps II ） of photosystem II （ PS II ）, and photochemical quenching coefficient （qp） of PMS were higher than those of PM and CK, the maximum increment values were 6.1%, 9.6% and 30.9% as compared with PM, and significant differences were observed in filling stage （P〈0.05）. The values of qN in PMS were lowest among the three treatments, and it decreased significantly by 23.8% and 15.4% in heading stage in 2012 and 2013 respectively, as compared with PM. The stoma conductance （gs）of wheat flag leaves in PMS was higher than that of PM and CK, with significant difference being observed in filling stage, and it increased by 17.1% and 21.1% in 2012 and 2013 respectively, as compared with PM. The transpiration rate （ Tr）, net photosynthetic rate （ Pn ）, and leaf instantane- ous water use efficiency （WUEi） except heading stage in 2013 of PMS increased by 5.4%-16.7%, 11.2%-23.7%, and 5.6%-7.2%, respectively, as compared with PM, and significant difference of WUEI was observed in flowering stage in 2012. The leaf area index （LAI） of PMS was higher than that of PM and CK, especially, it differed significantly in seasonal drought of 2013. Conse- quently, the PMS increased the SPAD values in flag leaves of spring wheat, and the capacity of flag leaves for photo energy assimilation and photosynthetic gas exchange were enhanced, caused more photosynthetic energy flowing into photochemical process, as well as decreased the heat dissipation, resulted in the increment of Pn and WUEi. Based on the higher Pn and LAI, the yield and WUE of PMS increased.