Influence of Physical Stress on Photosynthesis and Transpiration of Apple Leaves1

Abstract

Various treatments resulting in physical stress to leaves of apple ( Malus domestica Borkh.) were tested for their influence on net photosynthesis (Pn) and transpiration (Tr). Brushing to simulate handling or wind rubbing reduced both Pn and Tr in one study and had little effect in another. Shaking 1 min/day had no influence on Pn or Tr. Six or more 1-cm cuts/leaf reduced Pn and had no effect on Tr. Removal of 20% of the leaf area and twenty-four 1-cm cuts/leaf reduced Pn in young expanding leaves; the amount of cut surface exposed by injury was more important than the amount of leaf area removed. Scoring and feeding of two-spotted spider mites [ Tetranychus urticae (Koch)] reduced Pn.