Analysis of citrate accumulation during peach fruit development via a model approach.

摘要

A new model, based on the citrate model of Lobit et al., which is capable of reproducing the variation of citrate concn. with time in 2 peach cultivars, is described. The model calculates the rate of citrate synthesis or degradation as the product of a 'synthesis potential' and an 'efficiency level'. In the old model the 'efficiency level' was a simple linear function of temp. and respiration; however, in the new model its relationship with respiration was accounted for by a coeff. that decreased throughout fruit development. Differences in model parameters between the 2 cultivars were investigated. Late-maturing cv. Suncrest had markedly lower citrate synthesis potential than mid-maturing cv. Fidelia. The responses of citrate concn. to model parameters, temp., fruit respiration and growth curves were studied. The most important parameter in the new model, k4,2, represented the date when the relationship between respiration and 'efficiency level' changed from positive to negative. Increasing the mean temp. increased the citrate concn. at the beginning and decreased it near maturity for cv. Suncrest, while citrate concn. increased throughout fruit development and more strongly for cv. Fidelia. An increase in mesocarp dry wt. increased both fruit respiration and citrate concn. at the beginning of fruit development; near maturity it increased fruit respiration but decreased citrate concn. The model was also able to reproduce the effect of assimilate supply (leaf:fruit ratio). Further potential uses of the model are discussed.