Zhang Pangzhen, Wu Xiwen, Needs Sonja, Liu Di, Fuentes Sigfredo, Howell Kate
School of Agriculture and Food, University of MelbourneParkville, VIC, Australia.
Front Chem. 2017 Jul 7;5:48. doi: 10.3389/fchem.2017.00048. eCollection 2017.
Defoliation is a commonly used viticultural technique to balance the ratio between grapevine vegetation and fruit. Defoliation is conducted around the fruit zone to reduce the leaf photosynthetic area, and to increase sunlight exposure of grape bunches. Apical leaf removal is not commonly practiced, and therefore its influence on canopy structure and resultant wine aroma is not well-studied. This study quantified the influences of apical and basal defoliation on canopy structure parameters using canopy cover photography and computer vision algorithms. The influence of canopy structure changes on the chemical compositions of grapes and wines was investigated over two vintages (2010-2011 and 2015-2016) in Yarra Valley, Australia. The Shiraz grapevines were subjected to five different treatments: no leaf removal (Ctrl); basal (TB) and apical (TD) leaf removal at veraison and intermediate ripeness, respectively. Basal leaf removal significantly reduced the leaf area index and foliage cover and increased canopy porosity, while apical leaf removal had limited influences on canopy parameters. However, the latter tended to result in lower alcohol level in the finished wine. Statistically significant increases in pH and decreases in TA was observed in shaded grapes, while no significant changes in the color profile and volatile compounds of the resultant wine were found. These results suggest that apical leaf removal is an effective method to reduce wine alcohol concentration with minimal influences on wine composition.
去叶是一种常用的葡萄栽培技术，用于平衡葡萄藤植被与果实之间的比例。去叶操作在果实区域周围进行，以减少叶片的光合面积，并增加葡萄串接受阳光照射的程度。顶部叶片摘除并不常用，因此其对树冠结构及最终葡萄酒香气的影响尚未得到充分研究。本研究使用树冠覆盖摄影和计算机视觉算法，量化了顶部和基部去叶对树冠结构参数的影响。在澳大利亚亚拉谷的两个年份（2010 - 2011年和2015 - 2016年），研究了树冠结构变化对葡萄和葡萄酒化学成分的影响。设拉子葡萄藤接受了五种不同处理：不进行叶片摘除（对照）；分别在转色期和中等成熟度时进行基部（TB）和顶部（TD）叶片摘除。基部去叶显著降低了叶面积指数和叶幕覆盖度，并增加了树冠孔隙度，而顶部去叶对树冠参数的影响有限。然而，后者往往会使成品葡萄酒的酒精含量降低。在遮荫的葡萄中观察到pH值显著升高，总酸含量显著降低，而最终葡萄酒的颜色特征和挥发性化合物没有显著变化。这些结果表明，顶部去叶是一种有效降低葡萄酒酒精浓度且对葡萄酒成分影响最小的方法。
