Prohexadione-Ca positively affects gas exchanges and chlorophyll content of apple and pear trees

摘要

Prohexadione-Ca is a new generation growth retardant which inhibits dioxygenase enzymes activity mimicking 2-oxoglutarate and affecting both gibberellin and phenolic compounds metabolism. Several reports regarding the use of this growth retardant inapple and pear show the positive effects of prohexadione-Ca on yield and average fruit weight. On the contrary only a few trials have been performed regarding the effect of prohexadione-Ca on tree photosynthesis. This paper reports studies carried out over four-years on apple and pear to evaluate the photosynthetic efficiency of trees treated with prohexadione-Ca: whole-canopy experiments were performed on apple field trees, and leaf measurements on potted apple scions and field pear trees. Prohexadione-Ca positively affected leaf mass area and clorophyll content; net photosynthesis was often increased after application with the exception of a late spring application on vigorously growing trees. From these studies the positive influence of prohexadione-Ca on fruit weight and yield might be attributed to improved ecophysiological efficiency.