Role of calyx lobes in gas exchange and development of persimmon fruit

The role of calyx lobes in CO₂ exchange in persimmon (Diospyros kaki Thunb.) fruit was investigated during fruit growth and development. Carbon dioxide exchange rates of attached and detached fruit were measured in light and dark conditions in the field after calyx lobes were removed. Calyx lobes were removed at fruit growth stages I and III, which were defined as the period when fruit diameter increases >0.3 mm · d^-1 (Zheng et al., 1990). Removing calyx lobes at stage I significantly inhibited fruit growth, while removing them at stage III had no effect on growth. Two weeks after calyx lobes were removed at stage 1, CO₂ exchange decreased 80% in light and dark conditions compared with the control fruit. The rapid decreases of CO₂ exchange rate by calyx lobe removal at stage I were obvious if expressed per fruit or on a fresh weight basis. In contrast, treatment at stage III had no effect on CO₂ exchange rate of fruit and no effect on fruit growth. However, when the calyx lobe scars were sealed with Vaseline soon after calyx lobe removal at stage III, an immediate decline in CO₂ exchange rate in the dark occurred with simultaneous inhibition of the final swell in fruit growth. A possible relationship between fruit growth potential and gas-exchange capacity is discussed.