5. Conclusions
Over 30 years have elapsed since Williams (1965) first proposed the EPP
concept. The amount of work developed during this time has shown that highly variable values can be obtained for this parameter depending on cultivar, time and location. At first sight this may seem disappointing, since no particular values can be attributed to species or cultivars, and due to this high variability, calculation of the EPP on its own only illustrates particular cases. However, this apparent weakness constitutes its strength, since this variability is the reflection of variability in fruit set and on events occurring during the reproductive process. The EPP concept provides the tools to dissect and locate the causes for this variability, setting the frame to study the liming factors for adequate fruit set. This is the main reason why the EPP concept has stood the test of time. In perspective, this survival is based upon the fact that the parameters determining the EPP have a solid biological basis. Indeed, these parameters are the successive steps that take place during the reproductive process: stigmatic receptivity, pollen tube growth and ovule receptivity. Since these parameters are always present, the EPP remains a timely concept able to integrate in this frame any new effect that may modify the reproductive process.
5. ConclusionsOver 30 years have elapsed since Williams (1965) first proposed the EPPconcept. The amount of work developed during this time has shown that highly variable values can be obtained for this parameter depending on cultivar, time and location. At first sight this may seem disappointing, since no particular values can be attributed to species or cultivars, and due to this high variability, calculation of the EPP on its own only illustrates particular cases. However, this apparent weakness constitutes its strength, since this variability is the reflection of variability in fruit set and on events occurring during the reproductive process. The EPP concept provides the tools to dissect and locate the causes for this variability, setting the frame to study the liming factors for adequate fruit set. This is the main reason why the EPP concept has stood the test of time. In perspective, this survival is based upon the fact that the parameters determining the EPP have a solid biological basis. Indeed, these parameters are the successive steps that take place during the reproductive process: stigmatic receptivity, pollen tube growth and ovule receptivity. Since these parameters are always present, the EPP remains a timely concept able to integrate in this frame any new effect that may modify the reproductive process.
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