Orchard Planting Density and Tree Development Stage Affects Physiological Processes of Apple (Malus domestica Borkh.) Tree

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.

The Influence of Rootstock and High-Density Planting on Apple cv. Auksis Fruit Quality

“…Previous data showed that increased cv. Auksis tree density negatively affected photosynthesis intensity and other indices related with photosynthetic response [ 7 , 8 ]. The carbohydrates produced in the leaves are further transported to the fruit, so the amount of carbohydrates in the fruit strongly depends on the production in the leaves [ 13 , 26 , 27 ].…”

“…Our study confirmed that the planting density did not have a significant effect on the accumulation of sugars in the leaves of the apple tree cv. Auksis [ 8 ], and neither on the amount of sugars in the fruit ( Table 1 ). P 60 dwarfing rootstock and P 22 super dwarfing rootstock had different effects on carbohydrate content in fruits; significant differences were found for sorbitol and starch content ( Table 1 ).…”

“…However, increasing tree canopy during growth results in competitive stress. The increased density leads to decreased yields from the tree, but yields per unit area remain higher [ 6 , 7 , 8 , 9 ]. Seeking to grow high-density apple orchards efficiently, it is important to select the distances between the trees and the corresponding vigor rootstocks.…”

“…However, a well-chosen rootstock alone is not enough; the environmental conditions also change the composition and quality of the fruit. Sunlit canopies result in more active photosynthetic processes [ 8 , 25 ]. With insufficient sunlight, glucose and sorbitol produced during photosynthesis are transported to the apple fruit, where they can be stored as fructose, glucose, malic acid, or starch [ 13 , 26 , 27 ].…”

Converting Tall Spindle Apple Trees to Narrow Walls with Summer and Dormant Hedging Plus Root Pruning

“…Robinson et al (2013) suggested that the optimum planting density is approximately 2700 trees/ha, although super spindle orchards can be larger than 5450 trees/ha. Recent studies have examined densities as high as 13,000 trees/ha (Lauzike et al 2020), although more moderate estimations found peak productivity to be approximately 4762 trees/ha (Leão de Sousa and Gonc ¸alves 2022).…”