Estimation of the bioenergetic costs of fruit and other organ synthesis in apple

The specific bioenergetic cost of apple fruit (Malus domestica Borkh. cv. Braeburn) growth was calculated from seasonal elemental analysis (for carbon, hydrogen, nitrogen, and sulphur) and ash data. Specific cost changed during fruit development and at harvest was 1.16 g glucose g -1 dry weight of which 0.142 g glucose g -1 dry weight was consumed in growth respiration. Comparisons of those end-of-season values with those from a range of other apple cultivars (early through late maturing, and with a range of sugar/acid ratios) showed little difference, despite variations in elemental composition. Specific costs ranged between 1.15 and 1.16 g glucose g -1 dry weight, and growth respiration between 0.136 and 0.148 g glucose g -1 dry weight. Specific costs were also calculated for leaves (extension and spur), wood (1 and 2 year), and trunk and roots (fine and coarse). Leaves had the greatest cost (mean 1.44 g glucose g -1 dry weight), then wood and trunk (mean 1.38 g glucose g -1 dry weight), and fruit had the smallest. Specific growth costs were also calculated from heats of combustion data. Little difference was observed between the two methods, but the values calculated from the elemental analysis data tended to be higher than those calculated from the heats of combustion data.