| Zhanhuadongzao, famous for its very sweet, crisp, aboundant juice and vitamin fruit, is an elite variety of Ziziphus jujube Mill., which is mainly distributed in the Yellow River delta of China. One of the most important elements in jujube orchards management was vegetative growth regulation in this area due to excessive vegetative growth of Zhanhuadongzao trees, and which caused lower fruiting rate. Actually, shoot pruning, bark girdling and scoring were widely applied in production every year, which resulted in the weakness of tree vigor and liability to suffering from epiphyte and physiological diseases, and subsequently low fruit quality and frequently dead trees. As the biological characteristics, the effects of root pruning on jujube growth, metabolic mechanism, fruit quality and soil physio-chemical characteristics of six-year-old Zhanhuadongzao (Ziziphus jujuba Mill.) trees were evaluated. Three root pruning treatments (severe, moderate and light degree) were conducted at the distance of 3, 5 and 7 times trunk diameter from trunk on both inter-row sides of the trees, respectively. The results are as follows:1. Compared to the control, the root pruning of 3 times trunk diameter decreased the number, length and thick of twice branch by 12.1%, 27.9% and 3.9% in the first year, in the second year after root pruning, the number and length of twice branch were decreased by 31.7% and 16.1%, but thickness was increased by 37%, respectively.2. Both 3 and 5 times trunk diameter root pruning had no apparent effects on nitrogen (N), phosphorus (P) and potassium (K) contents of leaves after 35 days, but had significant effects at harvest time and the next year after root pruning in contrast to the control of no root pruning.3. In comprision to the control, Photosynthetic rate (Pn), Transpiration rate (Tr), Stomatal rate (Gs), Intercellular CO2 Concentration (Ci) of leaves were lowered after 35 days and were raised at harvest season as effected by the root cutting treatments of 3 and 5 times trunk diameter. There were distinct impacts on Pn, Tr, Ci and Gs between 3, 5 times trunk diameter and control in the second year of root pruning. Leaf chlorophyll content of Chinese jujube trees was highest under the treatment of 3 times trunk diameter root cutting, which declined gradually with the increase of root cutting distance and no significant differences at the second year.4. 3 times trunk diameter root pruning treatments, Auxin (IAA) concentrations and Ethylene (ETIH) release of twice branch top were higher than control after 35 days, while at harvest and the second year, IAA concentrations distinctly decreased and ETIH release was controry to IAA. Auxin (IAA) concentrations of root were increased after 35 days and decreased at harvest. Abscisic acid (ABA) and Zeatine (ZT) content of root cut by 3 times trunk diameter were both increased in the first year, but no evident difference of ABA content was found and ZT content was lower by contrast to control. Root pruning of 3 times trunk diameter strongly inhibitted growth of date top; by comparing to control, organelles, for example, vacuole, cell wall, golgi body, endoplasmie reticulum, mitochondria and plasmodesmata, were not rich in the cell by root pruning with 3 times trunk diameter. Compared with root cutting of 3 times trunk diameter, the effect of root cutting on the vegetative growth at the distance of 5 times trunk diameter was weakened to some extent.5. Compared to control, Peroxidase (POD), Catalase (CAT) and Malondialdehyde (MDA) leaf activities of 3 times trunk diameter were distinctly lowered in the first year and POD was indifference but CAT and MDA were more superior in the second year after root pruning.6. N, P and K contents in the rhizosphere soil of root pruned treatments were higher than that of control in the firest year, but which were contrary in the second year. In the firest year after root pruning the activities of invertase, catalase, phosphatase, urease and organic matter were lower and all were higher in the second year with the exception of organic matter. pH value was first, high to low among two years. Cypermethrin residues of rhizosphere soil under root pruning were higher than that of control in the course of two years.7. Compared with the control, the amounts of bacteria and fungi were significantly reduced by severe and moderate root pruning but unaffected by light pruning treatment. For actinomyces, no significant differences were found among all treatments. The amounts of microorganism population were increased in the second year. The effects of root pruning on amino acid, organic acid and total sugar were the same as bacteria and fungi.8. 3 times trunk diameter root pruning intensely inhitted the numbers of leaf, flower and date hanging but improved fruiting rate in the duration of two year after root pruning. There were no effects on yield between root pruning treatment and control. Total sugar and vitamin C were contrary to pesticide residues and hardness of fruit , compared to control, the former was higher , the later was lower in 2-year period. Contrary to total acid, soluble solid in the first year was decreased and on differences were found in the second year in contrast with control.9. All the treatment by root pruning and fertilization, there are more leaves in treatment 1, 5 and 9, less numbers of date hanging and flower in treatment 1, 2 and 3. For the twice branch, lower length and number in treatment 3, 7, and 11 and more thick in treatment 1, 2 and 5. Leaf chlorophyll content, total sugar, vitamin C, fruit rate and fertilizer utilization percent were higher in treatment 3, 7 and 11.It is proposed that the removal of root at 3 times trunk diameter distance from trunk was feasible to regulate growth and metabolic mechanism of Zhanhuadongzao tree, fertilization under root pruning of 3 times trunk diameter distance was the best treatment before bud and at fruit expanding stage with half and total fertilizing amount, respectively.
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