Physiological changes of fruit and C/N ratio in sugar apples (Annona squamosa L.) under drought conditions

The carbon/nitrogen (C/N) ratio in bearing sugar apple ('Fai') trees and the physiological changes of fruit under drought conditions were analyzed. The trees were divided into two test groups. In the first group, sugar apple trees were irrigated during the experiment (untreated control). In the second group, the trees were not watered for 30 days before harvest. Fruits and leaves were sampled 7, 14, 21, and 28 days after the drought treatment. It was found that the net photosynthesis, stomatal conductance, and chlorophyll fluorescence in drought trees were lower than those in the untreated control. Drought trees had lower leaf water content than the untreated control trees. Total sugar and proline concentrations in peel and pulp significantly increased under drought trees. In addition, the C/N ratio in leaves was increased under drought conditions. Drought conditions induced accumulation of total sugar and proline in the fruit. The result suggests that the drought conditions before harvest may improve fruit quality in sugar apples.