Effects Of Overhead Shading On Growth, Development Of Kiwifruit In Summer

In most kiwifruit production areas of China, hot summer conditions frequently result in severe premature fruit drop and leaf fall, decrease of fruit quality and storability and so on. In this study, Field vines of A. chinensis cultivars Cuiyu and A. deliciosa cultivar Miliang-1 were subjected to three levels treatment of 25%, 50% and 75% overhead shading from early July to late September, with un-shaded vines as the control.Result showed that: moderate shading markedly reduced leaf fall, almost completely eliminated fruit drop, observably improved yield and fruit quality, also markedly extended fruit storage life. Moderate shading showed no apparent effect on budburst and flower formation in the following year. The suitable level of shading for Cuiyu is about 25%; the treatment of 50% overhead shading is more appropriate to Miliang-1. However, over shading markedly decrease the content of SSC, TSS and TA, and reduce the rate of budburst and flower number of the following year.Shading markedly reduced light intensity, decreased canopy temperature increased the relative humidity, meanwhile decreased the temperatures of fruit surface and leaf surface, improved canopy microclimate conditions. And then, effectively eliminate the phenomenon of "midday depression". Under the treatment of 25% overhead shading, the Pn of Cuiyu was higher than other else; 50% overhead shading was more appropriate to Miliang-1 by improving the photosynthesis efficiency and reducing the midday depression. It concluded that Cuiyu cultivar has better tolerance to high temperature and strong light conditions than Miliang-1. 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 in kiwifruit. However, the level of shading should be tested carefully for individual cultivars to avoid the adverse effects of over shading.