CARBOHYDRATE REQUIREMENTS FOR DARK RESPIRATION BY PEACH VEGETATIVE ORGANS

The specific respiration rate at 20-degrees-C (R20) Of Peach leaves and stems declined rapidly from a high value in the early spring (22.5 nmol CO2 g(dw)-1 S-1) to relatively constant rates by July (3.1 nmol CO2 g(dw)-1 s-1). Leaf R20 declined more rapidly than current-year stem R20, but leaf and current-year stem R20s were similar by July. The R20 Of current-year stems in July was approximately 2.5 times greater than that of one-year-old stems (1.3 nmol CO2 g(dw)-1 s-1), and about 30 times greater than that of the trunk R20 (0.1 nmol CO2 g(dw)-1 s-1). The Q10s of leaves and stems were approximately 2 for a temperature increase between 20 and 30. The Q10s above 30 were 2.03 for leaves but only 1.61 for stems. Leaves and current-year stems accounted for 2 and 17% of the aboveground vegetative biomass in April and August, respectively, but accounted for 59-80% of total daily (24 h) respiration. Although trunk biomass accounted for 91 and 77% of aboveground vegetative biomass, in April and August, respectively, trunk respiration accounted for only 8-15% of daily aboveground respiration. Before harvest, during a period when fruit growth was source-limited, daily fruit respiration exceeded respiration by all aboveground vegetative organs.