Modelling the fresh matter accumulation for peach fruit growth

摘要

A model of fresh matter accumulation was developed for peach fruits during the stage of rapid mesocarp development. It was assumed that trees were optimally fertilized and that carbon acquisition by photosynthesis was sufficient for well irrigated trees to reach full potential fruit growth. The model was based on simple hypotheses of fluid flows into and out of the fruit. It was considered that the fruit receives a daily sap flow from the plant and releases water and carbon by transpiration and respiration. The model assumed that the sap flow to the fruit increases as the fruit water potential decreases and as the tree water potential increases. The fruit's water potential was assumed to decrease essentially in the same way as its osmotic potential, the latter depending on sugar concentration. The model assumed that sugar concentration increased with both fruit weight and transpiration per unit weight. The maximum daily shrinkage of the trunk was used as an indicator of tree water potential. Consequently the model assumed that sap flow increases with fruit weight along with transpiration per unit weight, and that it decreases with increase in the maximum daily shrinkage of the trunk. Fruit transpiration was assumed to increase with fruit size, which is related to skin permeability, and with global radiation. Fruit respiration was considered to be related to fruit growth and to temperature. The model allows simulation of the variability of growth between fruits according to climate conditions, level of water stress and fruit weight at the beginning of the simulation. An experiment conducted on cv. Dixired trees well watered or submitted to water stress was used partly for estimating the model parameters and partly for testing the model. The close agreement between simulated and field data supported the model.