Influence of orchard management system on canopy composition, light distribution, net photosynthesis and transpiration of apple trees

Abstract

In a study in Australia, eight orchard management systems with six year old ‘Granny Smith’ and ‘Starking Delicious’ apple trees on ‘Northern Spy’ rootstock were tested: free palmette, central leader, minimal pruning, Lincoln canopy, Tatura trellis, Ebro, Palmette, MIA. These were evaluated for their influence on canopy composition, light distribution (both quantity and quality), net photosynthesis (Pn) and transpiration (E). ‘Starking Delicious’ tended to have a greater density per unit of limb cross-sectional area of flowering, non-flowering spurs, and vegetative shoots than ‘Granny Smith’. For both cultivars the density of flowering spurs per unit limb area was higher in the Tatura trellis and Lincoln canopy than with the free-palmette and central leader trees. The Lincoln canopy and MIA resulted in a greater density of shoots than the palmette, free palmette or central leader. ‘Starking Delicious’ trees had higher levels of photosynthetic photon flux transmission (PPFT) to comparable positions in each canopy type and a greater percentage of their canopy above the 30% PPFT threshold, than ‘Granny Smith’. Trees in the Ebro system had lower values of PPFT at each date than those in the other systems. The palmette and free palmette systems tended to have the highest PPFT values and proportion of the canopy above 30% PPFT late in the season, but the differences were not significantly higher than the central leader, Lincoln canopy, and minimum pruned systems. PPFT values decreased from the top to the bottom of the canopy in all systems. PPFT declined from the periphery toward the centre of the canopy at each level in the following systems: Ebro, minimum pruned, Lincoln, palmette, and free palmette. In the Tatura trellis and MIA, particularly at the 120 and 170 cm canopy heights, PPFT increased from the canopy edges toward the tree centre. Light penetration (400-700 nm) and the red/far-red ratio were higher in the lower canopy for trees in the palmette and central leader trees than the other systems (Ebro, Tatura trellis, minimum pruned, Lincoln, MIA, free palmette). Orchard management system had little influence on Pn and E measured seven times over the season. Shoots had a higher Pn and E than flowering or nonflowering spurs, which did not differ from each other. Generally, the east side of the canopy had higher Pn rates than the west side, while E did not differ. Shoot leaves from the terminal or mid-areas of the shoot had higher Pn and E than basal leaves on the same shoot. The Pn light response curve of shoot leaves on the Palmette had a steeper slope than leaves on the Tatura trellis. Leaves from the lower levels of the canopy of all systems were more responsive to changing light at or above saturation.