Wünsche Jens N, Greer Dennis H, Laing William A, Palmer John W
HortResearch, Hawke's Bay Research Centre, Private Bag 1401, Havelock North, New Zealand.
Tree Physiol. 2005 Oct;25(10):1253-63. doi: 10.1093/treephys/25.10.1253.
Seven-year-old apple (Malus x domestica Borkh.) trees cv. 'Braeburn' on rootstock M.26 were flower-thinned to establish four crop loads, resulting in final mean fruit numbers per tree of 0, 100, 225 and 400. Mean fruit mass decreased by about 35% with each decrease in cropping density. Fruit from light-cropping trees had significantly advanced maturity as indicated by the harvest management criteria of background color and starch/iodine score, and other fruit quality characteristics such as soluble solids. Flesh firmness and dry matter also increased with decreasing crop load. Compared with fruiting trees, mean leaf photosynthetic rates of non-cropping trees were significantly lower (40%) between 75 days after full bloom (dafb) and fruit harvest, with a maximum reduction of almost 60% at 118 dafb. Photosynthetic activity decreased linearly with increasing concentration of leaf starch, but was positively and significantly related to stomatal conductance. Consequently, the accumulation of nonstructural carbohydrates in leaves of light-cropping or non-cropping trees may have led to end-product inhibition of photosynthesis. Increases in xanthophyll cycle carotenoids mediated non-radiative thermal energy dissipation in non-cropping trees, providing increased capacity for photoprotection but reducing photochemical efficiency.
对七年生的苹果（苹果属苹果种，品种为‘布瑞本’），砧木为M.26，进行疏花以设定四种负载量，最终每棵树的平均果实数量分别为0、100、225和400。随着种植密度的降低，平均单果质量下降了约35%。根据底色和淀粉/碘评分等采收管理标准以及其他果实品质特征（如可溶性固形物），轻负载树的果实成熟度显著提前。果肉硬度和干物质含量也随着负载量的降低而增加。与结果树相比，在盛花后75天（dafb）至果实采收期间，未结果树的平均叶片光合速率显著较低（40%），在118 dafb时最大降幅近60%。光合活性随着叶片淀粉浓度的增加呈线性下降，但与气孔导度呈正相关且显著相关。因此，轻负载或未结果树叶片中非结构性碳水化合物的积累可能导致了光合作用的终产物抑制。叶黄素循环类胡萝卜素的增加介导了未结果树的非辐射热能耗散，增加了光保护能力，但降低了光化学效率。
