Effect of root pruning on competitive ability in Chinese jujube tree

Abstract

-Introduction. The Chinese jujube tree always presents some unfavorable performances because its vegetative growth is very vigorous. Our study was conducted to apply root pruning to test whether it can effectively inhibit the vigorous vegetative growth by regulating the competitive ability of the root system for water and nutrients. Materials and methods. For our experiment, roots were cut at three different distances from the trunk (light, moderate and severe root pruning) on both inter-row sides of jujube trees to the depth of 20 cm. Roots of control jujube trees were not pruned. Then we determined for three years the competitive indicators of Chinese jujube trees including the length, number and thickness of primary branches; photosynthetic characteristics and nutrient concentrations of leaves; hormone contents in the jujube head, flower number and fruiting percentage, yield, and fruit quality. Results and discussion. In the early stage after root treatment, root pruning decreased lots of indicators such as concentrations of nitrogen, phosphorus, and potassium in leaves, photosynthesis, transpiration, stomatal conductance, and intercellular CO 2 concentration of leaves, relative to the same indicators as the control group. With the gradual emergence of new roots, these indexes appeared to have adverse patterns with respect to those in the early stage after root pruning. Compared with the control, root pruning significantly decreased the length and number of primary branches and flower number, but thickened primary branches, enhanced fruiting percentage and increased the amount of ethylene release of the jujube head in the whole experiment. Fruit quality was improved with root pruning, as indicated by increases in vitamin C and total sugar and a decrease in titrable acidity. No effects of root pruning were noticed on yield. From our results, we conclude that the removal of the root system at a distance of three times the trunk diameter (severe pruning) from the trunk is the most effective in regulating the competitive ability of the Chinese jujube tree.China / Ziziphus / root pruning / plant response / performance testing / agronomic characters / fruits / quality Effet de la taille des racines sur les performances du jujubier chinois.Résumé -Introduction. Le jujubier chinois présente toujours certaines performances désavantageuses du fait de sa croissance végétative très vigoureuse. Notre étude a été menée pour tester la taille des racines afin de vérifier si elle peut freiner efficacement la croissance végétative en régulant la compétitivité du système racinaire pour l'eau et les nutriments. Matériel et méthodes. Pour notre expérimentation, les racines de jujubiers chinois ont été coupées à trois distances différentes à partir du tronc (taille légère, modérée et sévère des racines), de chaque côté entre les rangs de jujubiers, à 20 cm de profondeur. Les racines des jujubiers témoins n'ont pas été taillées. Nous avons ensuite suivi pendant trois années certains indicateurs de compétitivité du jujubier...

Regulatory effects of root pruning on leaf nutrients, photosynthesis, and growth of trees in a closed-canopy poplar plantation

“…However, with the emergence of new roots, an increase in photosynthetic parameters was observed for the 8–2, 8–4, 10–2, and 10–4 treatments from the 2 nd to 5 th survey dates compared with CK. These findings are consistent with those obtained in previous studies [ 12 , 29 ].…”

“…The successful establishment and rapid growth of the trees depend on the fast growth and nutrient-absorbing ability of the root system. Previous preliminary studies on winter jujube and poplar illustrated that different intensities of root pruning have disparate effects on tree nutrition [ 4 , 12 ]; however, these studies only pruned the roots on two sides of each tree. In the current study, comprehensive methods of root pruning were implemented by combining three intensities (six, eight, or ten times the DBH from the trunk) and two orientations (two or four sides).…”

“…Plants are not able to absorb as much water and nutrients within a certain period of time after root pruning, mainly because the latter initially decreases the root surface area. With an increase in root-pruning intensity, the net photosynthetic rate, transpiration rate, and stomatal conductance correspondingly decrease [ 11 – 12 ]. Similar conclusions were drawn from the results from the first survey date in the current study.…”

“…In these treatments, the leaf transpiration rate decreased faster than the net photosynthetic rate , so that WUE increased, and was significantly higher than that of CK. This might be because the decline in stomatal conductance had less influence on photosynthesis than it had on transpiration [ 12 ]. Transpiration rate has a strong dependence on the stoma, thus partial stomatal closure would have been conducive to improving the WUE of the leaves.…”

“…Recent studies of Chinese winter jujube ( Ziziphus jujuba Mill.) found that root pruning significantly stimulated the germination of a large number of new roots at the incision site, increased root vitality, and expanded the absorption area of the root, thereby significantly improving the nutrition conditions and photosynthetic characteristics of the leaves [ 12 ]. The results of a previous study showed that root pruning of poplar can also improve rhizosphere soil fertility at the stage of canopy closing [ 4 ].…”