The effective pollination period in fruit trees

The effective pollination period (EPP) concept, was developed by Williams [J. Hort. Sci. 40 (1965) 31] to asses flower receptivity. It is defined as the number of days during which pollination is effective in producing a fruit and is determined by the longevity of the ovules minus the time lag between pollination and fertilisation. Over 30 years have elapsed since this concept was first introduced and, during this time, a good number of experiments have been carried out to study the EPP in different species and cultivars and under different environmental conditions. The results obtained indicate that the EPP plays a clear role controlling cropping in fruit trees and, consequently, it is a useful parameter to dissect and locate the factors limiting fruit set. In this paper, the information built up around the EPP is reviewed in temperate fruit trees. Since EPP is conditioned by three main processes - stigmatic receptivity, pollen tube kinetics and ovule development - the role played by each of them is examined. Finally, the influence of a number of factors - temperature, flower quality and chemical treatments - that affect those parameters is evaluated. (C) 2001 Elsevier Science B.V. All rights reserved.