“红富士”苹果离体／活体枝叶光合作用及水分利用效率的季节变化

The Seasonal Variation of the Photosynthesis and Water Use Efficiency of ‘Red Fuji'Apple in vitro/in vivo Leaves

以25a生“红富士”苹果为试材，于生长季节对饱和水分环境的离体枝条叶片与活体叶片的水势和光合作用进行了连续观测，以探索年周期内果树生长不同发育阶段叶片水分状况对光合作用和水分利用效率的影响。结果表明：在“红富士”苹果生育期前半阶段的展叶抽梢期、开花坐果期、花芽分化期，由于尚未进入降雨季节，叶片水势不断下降，光合速率和蒸腾速率都明显小于离体枝条叶片，叶片水势的降低在一定程度上限制了蒸腾速率，但是也同样降低了光合速率，导致水分利用效率逐渐下降。因此在4～5月份抽梢展叶期和开花坐果期应当及时进行灌水补充，6月份适度的水分胁迫则有利于花芽分化。在7、8月份冠层蒸腾作用强烈，叶片的水势下降明显，此时的水分胁迫限制了蒸腾速率，提高了水分利用效率。由于此期已经进入雨季，除个别干旱年份以外，通常无需灌溉。在9月份以后进入果树生长发育后期，随着日照时数和气温逐日下降，活体叶片的光合速率和蒸腾速率与离体枝条叶片的差异变小，树体的水分利用效率提高，一般不予灌溉。

Taking 25-year-old ＇Red Fuji＇ apple as material, seasonal leaf water potential and photosynthesis in-vitro and in-vivo of them were measured,in order to explore the changes of leaf water potential and its influence on photosynthesis and water use efficiency in different period of growth and development of fruit trees. The results showed that in the early stage of burgeon and leaf expansion, blossoming and fruit setting, flower bud differentiation, leaf water potential gradually decreased ,photosynthetic rate and transpiration rate were significantly lower than that in-vitro shoots. The decline of leaf water potential induced both transpiration and photosynthetic. Comprehensive analysis showed that WUE gradually decreased,and suggested that appropriate supplementary irrigation should be carried out in stage of burgeon and leaf expansion, blossoming and fruit setting in April and May. Moderate water stress was conducive to flower bud differentiation in June. In July and August, extent water potential decrease induced transpiration and WUE increased, and orchard irrigation was no needed unless continuance drought appeared in the rainy season in the trial district. After September,the WUE gradually enhanced, and the difference of photosynthetic and transpiration of in-vitro and in-vivo branches was decrescent, and there was no suggestion for orchard irrigation.