The Physiology of Growth in Apple Fruits VII. Between-Tree Variation of Cell Physiology in Relation to Disorder Incidence

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Abstract
Mean cortical cell size, soluble and protein nitrogen per cell, pre-climacteric respiration, mean fruit size, and incidence of disorders have been studied for fruit of each tree in a plot of 35 trees of Jonathan variety. These trees were remarkably uniform with regard to soil, aspect, tree size, and pollinating variety, but provided a range of mean fruit size per tree. There was a high degree of correlation between the variables. Cortical cell size increased with mean fruit size but more rapidly than would be expected from a proportional increase with size of fruit. Protein nitrogen increased proportionally with cell volume but the ratio of protein nitrogen and cell surface increased with cell size, suggesting that the protoplasm increased in thickness with cell size. Intercorrelation between respiration per cell, protein nitrogen, soluble nitrogen, and cell size were particularly close, remaining highly significant even when mean fruit size per tree was held constant by methods of partial correlation analysis, suggesting that these characteristics are functions of cell growth and are not influenced by between-tree differences due to cropping. Disorder incidence is correlated with the other variables and the implications of these relationships are discussed.