Physiological effects of prohexadione-calcium in apple trees: effects on parameters related to photoproductivity

SummaryDifferent prohexadione-Ca (RegalisTM, Pro-Ca) treatments were applied as foliar sprays to ‘Royal Gala’ and ‘Smoothee Golden Delicious’ apple trees to asses its effects on different physiological traits, under the growing condition of the Middle Ebro Valley (Spain). The application of Pro-Ca resulted in a decrease in leaf area, as well as fresh and dry leaf weights, and an increase in specific leaf weight. Greater light penetration through the canopy was recorded, indicative of a lower canopy density, resulting both from the inhibition of shoot growth and leaf extension growth. In addition, increases in leaf chlorophyll concentrations, and photosynthetic rates were found, which could account for the lack of effect of Pro-Ca on overall tree growth.