Influence of leaf area on net photosynthesis, yield and flower-bud formation in apple (Malus domestica Borkh.)

The influence of the artificial leaf area reduction (control, 30%, 50%, 70% defoliation) was studied on irrigated and non-irrigated apple trees of cvs . 'Elstar' and 'Jonagold' in two growing seasons. Photosynthesis was measur ed before and 12 days after defoliation in the first and second decade of J uly. The reduction of the assimilation area did not cause additional fruit dropping. Individual leaf photosynthesis varied significantly between diffe rent degrees of defoliation and different water treatments. Defoliation did not have any effect on the yield in the first growing season, whereas infl uence of defoliation on fruit quality was detected. Significant negative ef fect of defoliation on the reduction of flower bud formation as well as flo wering and consequently yield in following year was found. The assimilation area had a substantial effect on quantity, quality and yield regularity of apple trees.