Effect of root cutting on vegetative growth of Zizyphus jujuba Mill. 'Dongzao' trees.

The root system of six-year-old Chinese jujube trees were manually cut with a sharp spade at 3,5 or 7 times trunk diameter distance along both inter-row sides prior to buds break on April 26th2008 in Binzhou Chinese jujube orchards,to study the effects of root cutting on the vegetative growth.The results showed that the root cutting of 3 times trunk diameter decreased the length of once branch by 27.9% and the numbers of once branch by 12.1% in contrast to the control.Compared to the control,root cutting of 3 and 5 times trunk diameter had no apparent effects on N,P and K content of leaves after 35 days,but had significant effects after 161 days.Photosynthetic rate(Pn),transpiration rate(Tr),stomatal rate(Gs),intercellular concentration(Ci)of leaves and zeatin(ZT)content of root were lowered after 35 days and were raised after 161 days as effected by the root cutting treatments of 3 and 5 times trunk diameter.However,Auxin(IAA)concentrations of once branch top and root were increased after 35 days and decreased after 161 days.Also,ethylene release of once branch top and abscisic acid(ABA)content of root were both increased after 35 and 161 days.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.Leaf chlorophyll content of Chinese jujube trees was the highest under the treatment of 3 times trunk diameter root cutting,which declined gradually with the increase of root cutting distance.The contents of vitamin C and total sugar in fruits were increased by root cutting,but no effects were found on total acid content of fruit and yield at harvest.It is proposed that 3 times trunk diameter was the best distance for root cutting to regulate the vegetative growth of Chinese jujube trees.