Aspects of carbon supply and demand in apple fruits

Estimates of carbon available for fruit development are based on whole canopy gas exchange models as adjusted for relative Light interception by different shoot types that support fruit versus shoot growth. Estimates of the demand of the apple fruit were based on dry weight growth curves under non-limiting conditions, bioenergetic construction costs, and fruit respiration as affected by temperature and light exposure. The demand appears to increase rapidly after bloom, peaking about 4-6 weeks after bloom, then remaining quite stable to harvest. Supply/demand comparisons indicate that apple trees canopy carbon production cannot support all potential fruits for more than a week or more after bloom. During the season there appear to be two periods of potential carbon limitation for apple fruit growth; about 2-4 weeks after bloom and in the last weeks before harvest.