Abstract
The aim was to find out the impact of stress, caused by agrotechnological tools on photosynthetic behaviour of apple trees. The apple tree (Malus domestica Borkh.) cultivar Rubin was grafted on dwarfing rootstocks P60, planted in single rows spaced 1.25 m apart with 3.5 m between rows. In contrast to plant senescing reflectance index and nitrogen balance index, the photochemical reflectance index was significantly higher in 2018 compared with 2017. Such differences might be caused by drought stress on the summer and fast recovery before harvest time when measurements were made. The movement of nutrients and water disrupted by trunk incision had significantly negative effect on reflectance indices regardless on the year. Mechanical pruning with trunk incision and calcium-prohexadione lead to decreased dry to fresh weight ratio by 10–12% in first year of treatment. Mechanical pruning had significantly negative impact on photosynthetic rate, compared to pruning by super spindle it decreased 47%. Strong positive correlation between PRI and NBI 0,89–0,94, and strong negative correlations between PRI, NBI and PSRI −0.88 – (−0.91) were determined.
Highlights
The Photochemical Reflectance Index (PRI), which is based on leaf reflectance at 531 nm, is suitable for tracking variations in photosynthetic activity from leaf[10]
The movement of nutrients and water disrupted by trunk incision has significantly negative effect PRI
PRI was more than 50% lower by using trunk incision compared to control
Summary
The Photochemical Reflectance Index (PRI), which is based on leaf reflectance at 531 nm, is suitable for tracking variations in photosynthetic activity from leaf[10]. Other authors have investigated that changes in pigment content and ratio due to leaf growth, aging, or chronic stress play an important role along with xanthophyll pigment epoxidation in the PRI signal. While PRI characterizes the photosynthetic efficiency, the plant senescing reflectance index (PSRI) is sensitive to the changes of carotenoids and chlorophyll ratio and it was used as a quantitative measure of leaf senescence. They are both commonly used to describe the changing physiological state of vegetation[13,14,15]. Alarcon and Sassenrath[17] showed cotton leaf photosynthesis efficient dependence from shapes and canopy architecture. Fruit weight decreases by use of calcium-prohexadion. Trunk girdling increase fruit yield, and can increase the influence of other agrotechnical tools using foliar spray or fertilization[29,30,31,32]
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