夏季遮阴对猕猴桃园生态因子和光合作用的影响

Effects of overhead shading in summer on ecological factors and photosynthesis of kiwifruit orchard

以中华猕猴桃翠玉和美味猕猴桃米良一号为试材,研究高温季节(7月初-9月底)不同遮阴强度(0、25%、50%、75%)对猕猴桃园生态因子和光合作用的影响。结果表明:未遮阴的自然条件下,猕猴桃叶、果表面温度极高,蒸腾强烈,叶片光合作用出现严重的"午休"现象,表明树体处于严重的胁迫状态;遮阴可在一定程度上降温增湿,改善猕猴桃冠幕微环境,大大降低叶温和果温,有效消除叶片光合作用的"午休"现象。翠玉适宜的遮阴强度约为25%,米良一号约为50%。遮阴对翠玉叶片蒸腾速率无显著影响,但对米良一号的影响较大。可见,适度遮阴能有效缓解夏季高温强光对猕猴桃的危害,但过度遮阴有负面影响。

The vines of Cuiyu cultivar （belonging to Actinidia. chinensis Planch.） and Miliang 1 cultivar, （belonging to Actinidia. deliciosa Liang ＆ Ferguson） were subjected to threelevel treatments of 25%, 50% and 75% overhead shading from early July to late September, with un-shaded vines as control. Result showed that the temperatures of leaf surface and fruit surface, and transpiration rate were terribly high without shading, and photosynthesis was strongly inhibited around mid day. The vines were under severe stress during hot summer season. Shading markedly decreased canopy temperature, increased the relative humidity, meanwhile decreased the temperatures of fruit surface and leaf surface, and improved canopy microclimate conditions, and then, effectively eliminate the phenomenon of midday depression of photosynthesis. 25% overhead shading was more appropriate to Cuiyu cuhivar, improving the photosynthesis efficiency and reducing the midday depression, under the treatment of 50% overhead shading, the Pn of Miliang-1 was higher than other treatments. Shading showed no apparent effect on the TR of Cuiyu＇s leaves. But the leaf＇s TR of Miliang-1 was significantly affected by shading. The results indicated that overhead shading in summer could effectively overcome the harm caused by high temperature conditions for kiwifruit. However, the level of shading should be tested carefully for different cultivars in order to avoid the adverse effects of over shading.