South Australian Research and Development Institute, Waite Campus, Adelaide, South Australia, Australia.
Tree Physiol. 2011 May;31(5):494-9. doi: 10.1093/treephys/tpr043.
Conceptual models accounting for the influence of source:sink ratio on water relations of trees are theoretically relevant from a physiological perspective and practically important for irrigation scheduling. Midday stem water potential of horticultural trees often declines with increasing crop load but the actual response depends on environmental, management and plant factors. Here we advance a quantitative synthesis of the response of stem water potential to crop load from the perspective of phenotypic plasticity, defined as 'the amount by which the expression of individual characteristics of a genotype are changed by different environments'. Data sets of stem water potential for contrasting crop loads were compiled for apple (Malus domestica L. Borkh.), olive (Olea europea L.), peach (Prunus persica L.), pear (Pyrus communis L.) and plum (Prunus domestica L.). Phenotypic plasticity of stem water potential was calculated as the slope of the linear regression between stem water potential for each crop load and the environmental mean of stem water potential across crop loads. Regression lines for trees with different crop load diverged with decreasing environmental mean stem water potential. For the pooled data, plasticity of stem water potential was a linear function of relative crop load. This represents a significant shift in perspective: the effect of crop load on the trait per se (stem water potential) is environmentally contingent, but the effect of crop load on the plasticity of the trait is not. We conclude that research on the effects of crop load on tree water relations would return more robust results if plant traits are considered from the dual perspective of the trait per se and its plasticity.
从生理角度来看，考虑源库比对树木水分关系影响的概念模型具有理论相关性，并且对于灌溉调度具有实际重要性。园艺树木的中午茎水势通常随着作物负荷的增加而下降，但实际响应取决于环境、管理和植物因素。在这里，我们从表型可塑性的角度（定义为“基因型个体特征的表达因不同环境而改变的程度”）对茎水势对作物负荷的响应进行了定量综合。为对比作物负荷的苹果（Malus domestica L. Borkh.）、橄榄（Olea europea L.）、桃（Prunus persica L.）、梨（Pyrus communis L.）和李（Prunus domestica L.）编译了茎水势数据集。茎水势的表型可塑性被计算为每个作物负荷的茎水势与跨作物负荷的茎水势环境平均值之间线性回归的斜率。具有不同作物负荷的树木的回归线随着环境平均茎水势的降低而发散。对于汇总数据，茎水势的可塑性是相对作物负荷的线性函数。这代表了观点的重大转变：作物负荷对性状本身（茎水势）的影响是有条件的，而作物负荷对性状可塑性的影响则不是。我们得出结论，如果从性状本身及其可塑性的双重角度考虑植物性状，那么关于作物负荷对树木水分关系影响的研究将产生更可靠的结果。
