EFFECT OF THE MIST MICRO-SPRAY TIME ON PHOTOSYNTHETIC SPATIAL HETEROGENEITY OF GRAPE CANOPY

ABSTRACT In grape, high temperatures and low humidity prolong midday depression of foliar photosynthesis and dramatically reduce fruit yield. In this study, we explored the effects of various mist micro-spray treatments on grape photosynthesis at a test site in Shanshan County (N, 42.91°; E, 90.30°), Turpan, Xinjiang, China. We tested four different mist micro-spray durations including 1 h (WP1), 2 h (WP2), 3 h (WP3), and 0 h (CK). WP1, WP2, and WP3 affected canopy air temperature and humidity for 5 h, 7 h, and 9 h, respectively. At 12:30, WP1, WP2, and WP3 had the strongest cooling effect and altered temperature by −5.12 °C, −5.09 °C, and −5.17 °C respectively. The relative chlorophyll content was higher in the upper than the lower canopy leaves. There were no differences in the same leaf layers across treatments. The net photosynthesis and transpiration rates and stomatal conductance were higher for the upper than the lower canopy leaves. Compared with CK, the mist micro-spray treatments mitigated “midday depression” in the upper leaves and eliminated it altogether in the lower leaves. Mist micro-spray for 1 h d-1 most effectively improved grape leaf photosynthesis. The findings of the present study lay an empirical foundation for improving grape leaf photosynthesis and fruit yield.

摘要 葡萄遭遇高温低湿环境时，会延长叶片光合作用的午间低谷时长，并显著降低果实产量。本研究以中国新疆吐鲁番市鄯善县（北纬42.91°，东经90.30°）的试验田为研究区域，探究了不同微雾喷雾处理对葡萄光合作用的影响。本试验设置了4种不同的微雾喷雾时长处理，分别为1小时（WP1）、2小时（WP2）、3小时（WP3）及0小时（CK，空白对照）。WP1、WP2、WP3处理分别可使冠层空气温湿度维持效应持续5小时、7小时及9小时。在12:30时，WP1、WP2、WP3处理均表现出最强降温效果，分别使温度降低5.12℃、5.09℃及5.17℃。冠层上部叶片的相对叶绿素含量高于下部叶片，同一冠层层次的叶片各处理间均无差异。冠层上部叶片的净光合速率、蒸腾速率及气孔导度均高于下部叶片。与CK相比，微雾喷雾处理缓解了上部叶片的光合午间低谷现象，并使下部叶片的该现象完全消除。每日1小时的微雾喷雾处理最有效地提升了葡萄叶片的光合能力。本研究结果可为提升葡萄叶片光合能力及果实产量提供实证依据。