Consiglio per la ricerca in agricoltura e l'analisi dell'economia agraria, centro di ricerca Olivicoltura, Frutticoltura e Agrumicoltura (CREA - OFA), via Nursina 2, Spoleto (PG), Italy.
Dipartimento di Scienze Agrarie, Alimentari e Ambientali, Università degli Studi di Perugia, Borgo XX Giugno 74, Perugia, Italy.
Tree Physiol. 2018 Sep 1;38(9):1267-1277. doi: 10.1093/treephys/tpy011.
It has long been debated whether tree growth is source limited, or whether photosynthesis is adjusted to the actual sink demand, directly regulated by internal and environmental factors. Many studies support both possibilities, but no studies have provided quantitative data at the whole-tree level, across different cultivars and fruit load treatments. This study investigated the effect of different levels of reproductive growth on whole-tree biomass growth across two olive cultivars with different growth rates (i.e., Arbequina, slow-growing and Frantoio, fast-growing), over 2 years. Young trees of both cultivars were completely deflowered either in 2014, 2015, both years or never, providing a range of levels of cumulated reproductive growth over the 2 years. Total vegetative dry matter growth over the 2 years was assessed by destructive sampling (whole tree). Vegetative growth increased significantly less in fruiting trees, however, the total of vegetative and reproductive growth did not differ significantly for any treatment or cultivar. Vegetative growth over the 2 years was closely (R2 = 0.89) and inversely related to reproductive growth across all treatments and cultivars. When using data from 2015 only, the regression improved further (i.e., R2 = 0.99). When biomass was converted into grams of glucose equivalents, based on the chemical composition of the different parts, the results indicated that for every gram of glucose equivalent invested in reproductive growth, vegetative growth was reduced by 0.73-0.78 g of glucose equivalent. This indicates that competition for resources played a major role in determining tree growth, but also that photosynthesis was probably also enhanced at increasing fruit load (or downregulated at decreasing fruit load). The leaf area per unit of trunk cross sectional area increased with deflowering (i.e., decreased with reproductive growth), suggesting that water relations might have limited photosynthesis in deflowered plants, which had much greater canopies. Net assimilation rate (NAR) increased with reproductive growth and decreased with plant size. Net assimilation rate was also negatively correlated with the leaf area per unit of trunk cross sectional area, suggesting that water relations might have contributed to decreasing NAR at increasing plant size.
长期以来，人们一直争论树木的生长是受源限制的，还是光合作用会根据内部和环境因素直接调整到实际的汇需求。许多研究支持这两种可能性，但没有研究在整个树木水平上，在不同品种和果实负载处理下提供定量数据。本研究调查了不同水平的生殖生长对两个生长速度不同的橄榄品种（即生长缓慢的 Arbequina 和生长迅速的 Frantoio）整个树木生物量生长的影响，持续了 2 年。在这 2 年中，通过破坏性采样（整株）评估了总营养物质的生长情况。在任何处理或品种中，生殖生长的总干物质生长都没有显著差异。然而，结果表明，在结果实的树木中，营养生长显著增加较少。2 年来的营养生长与生殖生长密切相关（R2 = 0.89），并且在所有处理和品种中都呈相反关系。仅使用 2015 年的数据时，回归进一步提高（即，R2 = 0.99）。当将生物量转换为葡萄糖当量的克数时，根据不同部分的化学成分，结果表明，每投资 1 克葡萄糖当量用于生殖生长，营养生长就会减少 0.73-0.78 克葡萄糖当量。这表明资源竞争在决定树木生长方面起着重要作用，但光合作用也可能在增加果实负载时增强（或在减少果实负载时下调）。单位树干横截面积的叶面积随去花而增加（即随生殖生长减少），这表明在去花植物中，水关系可能限制了光合作用，因为去花植物的树冠更大。净同化率（NAR）随生殖生长增加而增加，随植物大小减小而减小。净同化率还与单位树干横截面积的叶面积呈负相关，这表明水关系可能导致随着植物大小的增加，净同化率降低。
