Magalie Jannoyer

Leaf-to-fruit ratio affects water and dry-matter content of mango fruit

Summary Changes in water and dry-matter content of developing mango fruit (Mangifera indica L. ‘Lirfa’) were investigated over a single season in Réunion Island, along with the effects of leaf:fruit ratio (10, 25, 50, 100 and 150 leaves per fruit on girdled branches). As the fruit developed, about 8–13% of fruit water weight was in the peel compared with 78–86% in the pulp and 6–9% in the stone. When the data were expressed on a dry-weight basis, 12–20% was in the peel, 60–70% was in the pulp and 18–20% in the stone. At harvest, larger fruit, on treatment 100, had a higher proportion of weight in the pulp. Good relationships between water and dry weight of each fruit component were found, regardless of the treatment. They showed that the rate of water accumulation decreased when the dry weight increased and that the dry-matter content increased as the fruit developed as well. Increasing leaf:fruit ratio to 100 leaves per fruit improved fruit yield by 300 g and pulp dry-matter content by 6%, for a total of 550 g and 20% at harvest. Fruit quality as estimated by pulp dry-matter content could be calculated easily during the changes in fruit weight over the season. Moreover, this indicator could be useful to assess the maturity of mango fruit.

A model of leaf photosynthesis for mango cv. Lirfa

The carbon status plays a key-role in flowering and fruiting of mango trees while influxes of carbohydrates seem to influence fruit size and taste. A model of carbon gain, losses and repartition between branch parts for mango is proposed. Photosynthesis represents the starting point of the modelling approach. The first step consisted of using 3D digitising to establish the relationship between the amount of leaf nitrogen per unit leaf area, N a and the gap fraction. The second step established the relationship between N a and the parameters of photosynthetic capacity derived from response curves of net photosynthesis to the intercellular CO 2 concentration (A-C i curves). Results are presented about this model. Its capacity for simulating leaf photosynthesis is also discussed.