Seasonal Trends in Net Photosynthetic Potential, Dark Respiration, and Specific Leaf Weight of Apple Leaves as Affected by Canopy Position1

Abstract

Changes in photosynthetic parameters in ‘Stayman’/Malling Merton (MM) 111 apple ( Malus domestica Borkh.) trees measuring 5 m wide and 4 m high were studied for an entire growing season. Parameters investigated included penetration of photosynthetically active radiation (PAR), changes in spur leaf net photosynthetic (Pn) potential, dark respiration (Rd) and specific leaf weight (SLW). As measured by changes in PAR penetration, canopy development was generally complete by mid-May. Pn, Rd, and SLW were modified by canopy position. SLW was influenced by the previous light environment as peripheral canopy leaves had higher SLW’s than interior leaves.