Search Results

You are looking at 1 - 2 of 2 items for :

  • Author or Editor: John W. Palmer x
  • Journal of the American Society for Horticultural Science x
Clear All Modify Search


Leaf areas on individual spurs were modified in the pink stage of flower development on ‘Golden Delicious’ apple (Malus domestica Borkh.), and the effects on fruiting, mineral content, and net photosynthesis (Pn), of leaves on those spurs determined. Removal of a 3mm-ring of bark from the spur increased initial fruit set, determined 1 week after petal fall, compared to normal spurs. The combination of ringing and removal of all leaves resulted in a complete loss of fruit. Final fruit set was reduced by any treatment involving ringing, reduction in spur leaf area, or injury to the stigmas. The greatest number and total weight of fruit at harvest were given by undefoliated, unringed spurs where the bourse shoot was allowed to develop. Ringing reduced Pn at petal fall but had no effect later in the season. Presence of the bourse shoot reduced Pn of spur leaves in early June. Spur leaves on fruiting trees had an important localized influence on fruit set, ultimate fruit size, and fruit Ca level of fruit produced on that spur.

Open Access

Effect of crop load on tree growth, leaf characteristics, photosynthesis, and fruit quality of 5-year-old `Braeburn' apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] trees on Malling 26 (M.26) rootstock was examined during the 1994-95 growing season. Crop loads ranged from 0 to 57 kg/tree [0 to 1.6 kg fruit/cm2 trunk cross sectional area (TCA) or 0 to 8.7 fruit/cm2 TCA]. Fruit maturity as indicated by background color, starch/iodine score, and soluble solids was advanced significantly on low-cropping trees compared to high-cropping trees. Whole-canopy leaf area and percentage tree light interception increased linearly with a significant trend as crop load decreased. From midseason until fruit harvest, leaf photosynthesis decreased significantly on lighter cropping trees and similarly, a positive linear trend was found between whole-canopy gas exchange per unit area of leaf and crop load. Leaf starch concentration in midseason increased linearly as crop load decreased, providing some explanation for the increased down-regulation of photosynthesis on trees with lower crop loads. After fruit harvest, the previous crop loads had no effect on leaf photosynthesis and preharvest differences in whole-canopy gas exchange per unit area of leaf were less pronounced. At each measurement date, daily whole-canopy net carbon exchange and transpiration closely followed the diurnal pattern of incident photosynthetic photon flux. The photochemical yield and electron transport capacity depended on crop load. This was due mostly to reaction center closure before harvest and an increased nonphotochemical quenching after harvest.

Free access