Physiological and biochemical responses of apple trees to irrigation water depth in a semiarid region of Brazil

ABSTRACT The present study evaluated the physiological and biochemical parameters of apple trees under different irrigation water depths in a semiarid region of Brazil. The experiment had a split-plot randomized block design. Irrigation levels (60, 80, 100, and 120% of the reference evapotranspiration - ET0) and two apple cultivars (Julieta and Princesa) were analysed in the experimental plots and the phenological stages (vegetative, flowering and fruiting) were analysed in the experimental subplots. The physiological characteristics evaluated included the chlorophyll index, relative water content, net photosynthesis, stomatal conductance, transpiration, internal CO2 concentration, leaf temperature and instant carboxylation efficiency. The biochemical characteristics evaluated included the leaf contents of reducing sugars, total soluble sugars, and non-reducing sugars and proteins. The best biochemical responses were observed in the Princesa cultivar under 80% ET0 during the flowering and vegetative stages and under 120% ET0 during the fruiting stage. The best physiological responses for all phenological stages were observed under irrigation levels of 120% ET0 for both cultivars. The cv. Princesa demonstrated osmotic adjustment under water stress conditions during the phenological stages evaluated.

摘要：本研究针对巴西半干旱地区不同灌溉水深下的苹果树，评估其生理与生化指标。本试验采用裂区随机区组设计。试验主区设置灌溉梯度（分别为参考蒸散量（reference evapotranspiration, ET0）的60%、80%、100%及120%）与2个苹果品种（Julieta及Princesa），副区则设置物候期（营养生长期、开花期与结果期）开展分析。本次评估的生理指标包括叶绿素指数、相对含水量、净光合速率、气孔导度、蒸腾速率、胞间CO₂浓度、叶片温度及瞬时羧化效率；生化指标则包括叶片中还原糖、总可溶性糖、非还原糖及蛋白质的含量。研究结果显示，Princesa品种在开花期与营养生长期的80% ET0灌溉条件下，以及结果期的120% ET0灌溉条件下，生化响应表现最优；两个苹果品种在所有物候期的生理响应最优值均出现在120% ET0的灌溉梯度下。此外，Princesa品种在本次评估的各物候期的水分胁迫条件下均表现出渗透调节能力。