Vol. 71 No: 5

Title:
Pmax as Related to Leaf: Fruit Ratio and Fruit Assimilate Demand in Peach

Authors:
M. BEN MIMOUN, J.-J. LONGUENESSE and M. GENARD

pp: 767-776

Abstract:
To estimate the effect of leaf:fruit ratio on peach leaf light-saturated photosynthesis, experiments were conducted on the early maturing cv. Alexandra in 1992 and late maturing cv. Suncrest in 1992, 1993 and 1994. In early May, the leaf:fruit ratios of bearing shoots were adjusted. The exchange of assimilate between the shoot and the rest of the tree was prevented by girdling the base of the shoot. Leaf photosynthesis measurements were made under saturating irradiance using a portable leaf photosynthesis system. Our results show that there was a significant effect of the leaf:fruit ratio on leaf light-saturated photosynthesis (Pmax). There was a reduction of P*max when the leaf:fruit ratio was high. To describe the effect of fruit demand on photosynthesis, we developed a hyperbolic model in which we assumed that Pmax is a function of fruit demand. The model is defined by two parameters: Pmax, the potential light-saturated photosynthesis, and K_D, the initial slope of the response curve of Pmax vs. fruit demand. We found no difference between cultivars and among years, so we developed a model which utilized all data.

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