FUNCTIONAL APPROACH TO THE RELATIONSHIPS BETWEEN FRUIT AND SHOOT DEVELOPMENT IN THE PEACH

Wf being the total dry matter of fruit per m of leader and Ws the total dry matter of shoots for the same productive unit, checked at almost weekly intervals, the growth curves of the two types of organ plotted against time (t) were adequately representable by a polynomial exponential function (W = e f(t)), where W stands respectively for Wf and Ws and f(t) is a 3rd or 4th degree polynomial respectively for shoots and fruit.

The relative growth rate (RGR) was of no use in understanding the natural fruit drop phenomenon, probably because such a parameter does not take into consideration the fact that the fruit is a prevalently parasitic organ, whose growth is linked to the afflux rate of metabolites produced elsewhere rather than in its own mass.

Conversely, the absolute growth rate (AGR) appeared to be closely linked to fruit drop variations, enabling us to form the hypothesis that these variations are the consequence of a negative balance between fruit and shoot growth rates and the rates of metabolite translocation from reserve organs (roots, trunk and branches) and/or from leaves.