Abstract
One of the most important factors affecting photosynthesis and metabolism is light absorbance by leaves and penetration through the canopy. The aim of this study was to evaluate the influence of planting density and tree development stages on photosynthetic activity, photosynthetic pigments, and carbohydrates in apple (Malus domestica Borkh.) trees in a combined way. The apple tree, Auksis, was grafted on dwarfing rootstock P 22. Space between rows was 3 m, trees were planted in 2001 in four distances: 0.25 m, 0.50 m, 0.75 m, and 1.00 m. Measurements and leaf samples were taken in the end of May (leaves fully expanded BBCH 20–25), in the middle of July (beginning of apple maturity BBCH 73–75) and at the end of August (harvest time BBCH 87–88) according BBCH—growth stages. Photosynthetic rate was significantly the lowest in the spring and tended to rise until fruit ripening, when it increased up to 19.4% compared to spring. Significantly the highest chlorophyll b and carotene α and β contents were found at the BBCH 73–75. The lowest levels of fructose and sorbitol in leaves were found at BBCH 73–75. The amount of starch accumulated in the leaves increased three times in summer compared to spring. Reduced distance between trees to four times (from 1 m to 0.25 m) showed clear competitive stress, as the decrease of photosynthetic rate (up to 36.4–38.6%) and total starch (up to 37–53%) was observed. The photosynthetic behaviour of apple trees was significantly affected by the development stage during the particular season which is related with physiological changes of metabolites transport and their distribution during fruit ripening and leaf senescence.
Highlights
One of the most important factors affecting photosynthesis and metabolism is light absorbance by leaves and penetration through the canopy
The rate of photosynthesis mostly depends on the photoperiod; During the growing the leaves rate ofare photosynthesis mostly depends the photoperiod; research showedseason, that young more photosynthetically activeon during the long day, research showed that young leaves are leaves more photosynthetically activedecrease during the day, and the rate of photosynthesis decreases as the age [26,30]
Photosynthetic indices were influenced by seasonality and by the distance between the trees. These changes may be affected by the light penetration in the canopy (Table 1) and competition for nutrients photosynthetic rate continued to increase till fruit harvesting (Figure 2)
Summary
One of the most important factors affecting photosynthesis and metabolism is light absorbance by leaves and penetration through the canopy. The composition of light changes during the day and as well as during the season [1]. Studies have shown seasonal changes in photosynthetic processes and pigments that are associated with leaf spring development and autumn aging [2,3]. Metabolic changes associated with nutrient resorption underpin the temporal variation of respiratory and photosynthetic rates once senescence starts. In mid-latitude regions with marked climate seasonality, changes in photosynthetic processes and metabolism are due to concurrent changes in leaf age and environmental conditions [4,5]. Leaf age affects light absorption and utilization, and protection systems against excess light
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