Quantitative analysis of relationships between inflorescence size, bearing-axis size and fruit-set - An apple tree case study

Inflorescence size was investigated in a range of apple tree cultivars. Each inflorescence size was quantified by the number of foliage leaves and flowers. A first analysis was carried out using dependence stereograms and standardized non-parametric correlation coefficients, based on Kendall's tau. The results generally showed a positive correlation between the numbers of leaves and flowers within an inflorescence. A second analysis was based on the consideration that each inflorescence was terminal on a subtending axis, and that inflorescence size was a dependent variable for two factors: the length of the subtending axis and 'wood age' (inflorescences were on 1-, 2- or 3-year-old wood). Two points were highlighted: the low total number of appendages of 1-year-old wood inflorescences, particularly the low leaf numbers. and the positive correlation between the length of the subtending axis and the leaf numbers (and to a lesser degree flower numbers). A third analysis revealed that fruit-set was positively correlated with leaf numbers and to a lesser extent with flower numbers. These results showed that fruit-set is an outcome of a chain of causally-related events, basically involving the inflorescence position within the tree architecture, which affects the vegetative growth of the subtending stem, and in turn strongly determines inflorescence development. These morphological observations are discussed in relation to some associated functional aspects. (C) 1996 Annals of Botany Company