滴灌水分亏缺对猕猴桃生育前期光合特性的影响

The Effect of Deficit Drip Irrigation on Photosynthetic Characteristics of Kiwifruit

【目的】探究滴灌水分亏缺对南方季节性干旱区猕猴桃生育前期光合特性的调控效应,为南方季节性干旱区猕猴桃节水高产种植提供理论依据。【方法】以9a生"金艳"猕猴桃为研究试材,以充分灌溉为对照(CK),分别在抽梢展叶期(I)、开花坐果期(II)设置轻度、中度、偏重度及重度4种亏缺水平(记为LD、MD2、MD1及SD,灌水量分别为CK的85%、75%、65%、55%),分析了滴灌水分亏缺对猕猴桃生育前期叶片光合特性的影响。【结果】水分亏缺显著降低猕猴桃生育前期叶片净光合速率(Pn)、蒸腾速率(Tr)和气孔导度(gs),且降幅均随亏水度加重而增大,但Pn降幅小于Tr和gs;与CK相比,I-MD1处理和II-MD2处理的Pn分别降低16.3%和6.5%,但叶片瞬时水分利用效率(WUEi)、叶片内在水分利用效率(WUEn)分别较CK提高7.7%、15.6%和8.1%、18.2%(P<0.05);水分亏缺后复水显著提高猕猴桃叶片Pn,其中I-LD处理复水后Pn较CK提高4.2%(P<0.05),达到5.94μmol/(m2·s),出现超补偿效应;Tr、gs与水汽压差(Δe)均呈二次曲线关系,Δe小于25×102 Pa时,Tr随Δe增大显著增大,Δe大于17×102Pa时,gs随Δe增大而明显降低。【结论】I-LD处理可在抽梢展叶期节水15%的情况下使猕猴桃叶片Pn提高4.2%,II-MD2处理可节约25%开花坐果期灌溉用水且使猕猴桃WUEi、WUEn分别提高8.1%、18.2%,是南方季节性干旱区猕猴桃生育前期适宜的滴灌水分调控模式。

【Objective】This paper aims to unveil the effect of regulated deficit drip irrigation on photosynthetic characteristics of kiwifruit at its earlier growth stage by comparative experiments in attempts to provide a guidance for constructing water-saving and high-yield kiwifruit production in seasonally arid areas in southern China.【Method】 The experiment compared five irrigation levels: sufficient irrigation(CK), and four other irrigations using 85%(LD), 75%(MD2), 65%(MD1) and 55%(SD) of the water used in the CK respectively.We took the variety of Jinyan as our model plant and the deficit irrigations were introduced at bud burst-leafing stage(I) or flowering-fruit set stage(II) respectively.Overall, we had eight treatments, excluding the CK.In all treatments and CK, we measured the photosynthetic indices.【Result】Deficit irrigations reduced net photosynthetic rate(Pn), transpiration rate(Tr), stomatal conductance(gs) of the kiwifruit significantly.All these reductions increased with water deficit, despite Tr and gs decreasing faster than Pn.Compared to CK, I-MD1 and II-MD2 reduced Pn by 16.3% and 6.5% respectively, while increased the instantaneous water use efficiency(WUEi) and intrinsic water use efficiency(WUEn) at leaf level by 7.7% and 15.6%, and 8.1% and 18.2%(P<0.05) respectively.Irrigation after a period of drying significantly increased Pn for the kiwifruit leaves and compared to CK, I-LD increased Pn by 4.2% to 5.94 μmol/(m2·s)(P<0.05), indicating the rewetting could overcompensate the loss during the dry period.Both Tr and gs varied with the vapor pressure difference(Δe) quadratically, with Tr increasing significantly with Δe when the vapor pressure difference(Δe) was less than 25×102 Pa.In contract, gs was significantly reduced when Δe was higher than 17×102 Pa.【Conclusion】 The I-LD treatment increased Pn of the kiwifruit by 4.2% while in the meantime saving 15% of water in bud burst-leafing stage, compared to the CK.The II-MD2 saved 25% of water in the flowering-fruit set stage while in the meantime increasing WUEi and WUEn of the kiwifruit by 8.1% and 18.2% respectively.As such, II-MD2 is the optimal deficit drip irrigation at the earlier growth stage of the kiwifruit growing in the seasonally arid areas in southern China.