微咸水-淡水交替灌溉对夏玉米光合日变化的影响

Effects of Alternate Fresh and Brackish Water Irrigation on the Diurnal Variation of Photosynthesis of Summer Maize

【目的】探究微咸水-淡水交替灌溉对夏玉米不同生育期内光合日变化的影响。【方法】以全生育期灌溉淡水处理(0.08 g/L Na Cl)为对照(CK),采用3种不同矿化度(1、3、5 g/L Na Cl)微咸水和淡水在夏玉米的3个不同生育期内(壮苗期、拔节抽雄期、灌浆成熟期)进行避雨盆栽交替灌溉试验。【结果】壮苗期及灌浆成熟期微咸水灌溉处理和CK的净光合速率(Pn)日变化均呈双峰曲线,壮苗期峰值出现在12:00和16:00,灌浆成熟期峰值提前至10:00和14:00。拔节抽雄期灌溉微咸水处理的Pn日变化呈单峰曲线,峰值提前至10:00。微咸水灌溉均引起夏玉米Pn和蒸腾速率(Tr)不同程度减小,导致水分利用效率(WUE)减小,玉米光合能力下降。壮苗期灌溉1 g/L微咸水和灌浆成熟期灌溉微咸水导致气孔导度(Gs)减小和胞间CO2摩尔分数(Ci)减小,通过气孔原因造成玉米光合作用减弱,而壮苗期灌溉3 g/L和5 g/L微咸水和拔节抽雄期灌溉微咸水导致Gs减小和Ci增大,通过非气孔原因导致玉米光合作用减弱。【结论】拔节抽雄期灌溉微咸水对夏玉米光合日变化影响最显著,壮苗期次之,灌浆成熟期最小,因此,微咸水-淡水交替灌溉制度应在夏玉米拔节抽雄期灌溉淡水,可在灌浆成熟期灌溉微咸水。

[Objective] Investigate the effects of alternate irrigation with fresh and brackish water on diurnal variation of photosynthesis of summer maize （Zea mays L.） in different growth periods. [Method] A pot experiment was carried out with three alternate fresh and brackish water irrigation methods. The various levels brackish wa- ters were irrigated respectively at the seedling stage （i.e. BFFI： 1 g/L NaC1, BFF3：3 g/L NaC1 and BFF5：5 g/L NaC1）, the jointing and tasseling stage （i.e. FBFI： 1 g/L NaC1, FBF3：3 g/L NaC1 and FBF5：5 g/L NaC1）, and the filling stage （i.e. FFBI： 1 g/L NaC1, FFB3：3 g/L NaC1 and FFB5：5 g/L NaC1）. The control treatment （CK） was set with fresh water （0.08 g/L NaC1） irrigation throughout the whole growth period. [Result] The net photosynthetic rate （Po） under BFF1, BFF3, BFF5 and CK treatments charged with double peak curves, and the majority of peaks appeared at 12：00 and 16：00. The similar trends were found in FFB1, FFB3 and FFB5 treatments while the majority of peaks appeared at 10：00 and 12：00 in advance. Diurnal variation Of Pn was expressed as a single peak at 10：00 in FBF1, FBF3 and FBF5 treatments. The Pn, transpiration rate （T0 and water use efficiency （WUE） of maize with brackish water treatments were reduced in different degree compared with the control treatment which resulting in decrease of photosynthesis. Moreover, these reductions were found in stomatal conductance （Gs） and intercellular CO2 concentration （Ci） （increase in BFF3, BFF5, FBF1, FBF3 and FBF5 treatments） which causing decrease of photosynthesis by stomatal and non-stomatal factors. [Conclusion] The effect of brackish water irrigation on diurnal variation of photosynthetic of maize is the most significant in the jointing and tasseling stage, followed by the seedling stage, while the effect is the minimum in the filling stage. So, sum- mer maize is seriously sensitive to brackish water irrigation in the jointing and tasseling stage. Fresh water should be applied in the jointing and tasseling stage and brackish water can be irrigated in the filling stage.