Estimation of the bioenergetic costs of fruit and other organ synthesis inapple

The specific bioenergetic cost of apple fruit (Malus domestica Borkh. cv. B raeburn) growth was calculated from seasonal elemental analysis (for carbon , hydrogen, nitrogen, and sulphur) and ash data. Specific cost changed duri ng 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/aci d ratios) showed little difference, despite variations in elemental composi tion. Specific costs ranged between 1.15 and 1.16 g glucose g(-1) dry weigh t, and growth respiration between 0.136 and 0.148 g glucose g(-1) dry weigh t. Specific costs were also calculated for leaves (extension and spur), woo d (1 and 2 year), and trunk and roots (fine and coarse). Leaves had the gre atest cost (mean 1.44 g glucose g(-1) dry weight), then wood and trunk (mea n 1.38 g glucose g(-1) dry weight), and fruit had the smallest. Specific gr owth costs were also calculated from heats of combustion data. Little diffe rence 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.