Photosynthetic Compensation to Partial Leaf Area Reduction in Sour Cherry

Abstract

The leaf surface area of l-year-old, potted `Montmorency' sour cherry (Prunus cerasus L.) trees was reduced by punching disks from some or all leaves to determine the threshold level of leaf area removal (LAR) necessary to reduce net CO2 assimilation (A) and whole-plant growth. Removal of 30% of the leaf area of individual leaves reduced A on a whole-leaf basis between 1 and 3 weeks following LAR. Less than 30% LAR was compensated for by higher estimated carboxylation efficiency and ribulose-l,5-bisphosphate (RuBP) regeneration capacity. The threshold level of LAR based on gas exchange of individual leaves was 20%. Although whole-plant dry weight accumulation was reduced at all levels of LAR, a disproportionately large decrease in dry weight occurred as LAR increased from 20% to 30%. This result indicates that 30% LAR exceeded the threshold LAR level that was noted for A (20% LAR). Wound ethylene production induced by leaf-punching ceased after 24 hours, which indicated that wounds had healed and that ethylene, therefore, did not influence A significantly. The observed threshoId of 20% LAR represents a significant compensation ability for sour cherry, but this threshold may change with crop load, environment, or both.