Abstract This study tested the possibility of improving whole-canopy water use efficiency (WUE) of grapevines (cv. Bobal) by maximizing radiation interception during the mornings and limiting this during the afternoons, when the vapour pressure deficit and the evaporative demand are higher. The three-year study consisted of two trials conducted in parallel on North-South row oriented potted- and field-grown grapevines. In both trials, performance in terms of vine water use, yield and WUE in a vertical shoot positioned (VSP) system was compared with that of vines leaned 30° towards West (WSP). Potted vines were fully irrigated, whereas field-grown vines were submitted to rain-fed and deficit irrigation conditions. In potted plants, there was no difference in daily transpiration between vines from the WSP and VSP treatments, but transpiration in the mornings was higher in WSP vines. Dry matter and berry size increased in WSP compared to VSP vines. In the field, watering regime had a greater effect than canopy inclination on vine performance. Nonetheless, the WSP system increased leaf area by 13%, yield by 12% and WUE by 11% compared to VSP, although differences in WUE were not statistically significant and the effect on yield was negligible under rain-fed conditions. In both trials, the WSP system did not have a major effect on grape composition (soluble solids, pH, total acidity, concentrations of anthocyanins and polyphenols). In conclusion, this pioneering three-year study proved that leaning vine canopies to the West increased grapevine performance despite the great effect that environmental conditions exerted each year on the data obtained. Further research is required to study the effects of different patterns of light interception on carbon balance and grape biochemical composition.

中文翻译：

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地中海条件下西斜葡萄树冠对水分利用效率和产量的影响

摘要 本研究测试了通过在早晨最大化辐射拦截并在下午限制辐射来提高葡萄藤 (cv. Bobal) 全树冠水分利用效率 (WUE) 的可能性，因为此时蒸汽压不足和蒸发需求较高。为期三年的研究包括在南北行定向盆栽和田间种植的葡萄藤上平行进行的两项试验。在这两项试验中，将垂直芽定位 (VSP) 系统中葡萄藤用水、产量和 WUE 方面的性能与向西倾斜 30° (WSP) 的葡萄藤进行了比较。盆栽葡萄藤得到充分灌溉，而田间种植的葡萄藤则处于雨养和缺水灌溉条件下。在盆栽植物中，来自 WSP 和 VSP 处理的葡萄藤之间的每日蒸腾量没有差异，但 WSP 葡萄树在早晨的蒸腾作用更高。与 VSP 葡萄藤相比，WSP 中的干物质和浆果大小有所增加。在田间，浇水制度比树冠倾斜度对葡萄树性能的影响更大。尽管如此，与 VSP 相比，WSP 系统使叶面积增加了 13%，产量增加了 12%，WUE 增加了 11%，尽管 WUE 的差异没有统计学意义，而且在雨养条件下对产量的影响可以忽略不计。在这两项试验中，WSP 系统对葡萄成分（可溶性固体、pH、总酸度、花青素和多酚的浓度）没有产生重大影响。总之，这项开创性的三年研究证明，尽管环境条件每年对所获得的数据产生巨大影响，但向西倾斜的藤蔓树冠提高了葡萄藤的表现。