Abstract:  With barrel planted red Fuji apple saplings as test materials,experiments which had four levels of irrigation(W₁ ,sufficient irrigation; W₂,mild water stress; W₃,moderate water stress; W₄,severe water stress.The lower and upper limits of irrigation were 75%—90%，65%—80%，55%—70% and 45%—60% field capacity,respectively) and three levels of fertilization( F₁，higher level; F₂,medium level; F₃，lower level.The N,P₂O₅ and K₂O were 0.6，0.2，0.2 g/kg，0.4，0.2，0.2 g/kg and 0.2,0.2,0.2 g/kg,respectively) were conducted to study the effects of water and fertilizer coupling on growth,photosynthetic characteristics and water use efficiency of two-year young apple tree under the drip irrigation.The results showed that compared with F₃W₄ treatment,F₁W₁treatment increased plant growth and leaf area by 85.2% and 74.5% respectively,while F₁W₂treatment increased plant growth and leaf area by 98.7% and 87.3% respectively,which indicated that the combination of high fertilizer and mild water deficit (F₁W₂treatment) was most conducive to the plant and leaf growth of young apple tree. The maximum val ues of water use efficiency occurred in F₁W₂treatment at each growth stage(germination and flowering stage,new growth stage,fruit setting and expanding stage and maturation stage) and were 3.49,3.84,4.37 and 3.90 mmol/mol，respectively.Meanwhile，compared with F₁W₁,although the net photosynthetic rate decreased by 1.9%,7.2%,6.8% and 2.1% respectively,the water use efficiency increased by 5.8%，6.7%，4.5% and 3.2% respectively,which indicated that the moderate water deficit could im prove the water use efficiency of young apple trees.Moreover,the maximum differences of net photosyn thetic rate and transpiration rate of apple saplings under different treatments all occurred in the fruit set ting and expanding period,which indicated that the fruit setting and expanding period of young apple tree was the most critical period of water and fertilizer demand,during which reasonable regulation of water and fertilizer could promote the growth of young apple trees．

Key words:  Apple, Coupling of water and fertilizer, Growth, Photosynthetic characteristics, Water use efficiency

摘要： 在滴灌条件下，以2年生桶栽红富士苹果幼树为试验材料，设供水和施肥2个因素，供水设4个水平（充分供水W₁、轻度亏缺W₂、中度亏缺W₃和严重亏缺W₄，其灌水上下限分别为75%~90%、65%~80%、55%~70%和45%~60%田间持水量），施肥设3个水平（高肥F₁、中肥F₂和低肥F₃，其N、P₂O₅、K₂O质量分数分别为0.6、0.2、0.2 g/kg，0.4、0.2、0.2 g/kg和0.2、0.2、0.2 g/kg），研究水肥耦合对苹果幼树生长状况、光合生理特性以及水分利用效率的影响。结果表明,对比F3W4处理，F₁W₁处理植株生长量和叶面积分别提高85.2%和74.5%，F₁W₂处理植株生长量和叶面积分别提高98.7%和87.3%，这说明高肥和轻度水分亏缺水肥组合（F₁W₂处理），最有利于苹果幼树植株和叶面积的生长。水分利用效率的最大值均出现在F₁W₂处理，萌芽开花期、新稍生长期、坐果膨大期和成熟期分别为3.49、3.84、4.37、3.90 mmol/mol，与高水高肥的F₁W₁处理相比，虽然各生育时期净光合速率分别减少1.9%、7.2%、6.8%、2.1%，但水分利用效率分别提高5.8%、6.7%、4.5%、3.2%，这说明适度的水分亏缺可以提高苹果幼树的水分利用效率。不同水肥耦合处理下苹果幼树净光合速率和蒸腾速率差异最大值均发生在坐果膨大期，这说明苹果幼树坐果膨大期为需水需肥的最关键时期，此时期合理的水肥调控可促进苹果幼树的生长。

关键词: 苹果, 水肥耦合, 生长量, 光合特性, 水分利用效率