Study Of Nutrient Elements And Endogenous Hormone On Longan Trees With Heavy Retractive Pruning

Heavy retractive pruning was carried out on the longan trees (Dimocarpus longan Lour. cv. Dawuyuan) which intersected each other. The trees were pruned bock to a average height of 1.1m from 4.3m. After pruning, PP333 ,CEPA and KCLO3 were applied to adjust growth and promote flowering of treated trees. The mineral nutritions and endogenous hormone contents were tested after implementing heavy retractive pruning. The results showed as follows:1 .The effects on shoots growth The shoot growth was stimulated greatly after implementing heavy retractive pruning. The growth of trees becomed less vigorous as the times of flush increased, PP333 restrained the growth of shoots. While trees with normal pruning showed a moderate growth without water shoots.2.The effects on nutrient element contents N, P, K, Ca, Cu and Zn contents in the leaves reduced after implementing heavy retractive pruning; Mg and Zn contents in the leaves of trees of heavy retractive pruning + winter flush controlling increased remarkably. In the critical period of bud physiological differentiation of longan, N, P, Mg, Mn, Cu and Fe contents in the leaves of trees of normal pruning + winter flush controlling with CEPA were higher than those of others. There was not a regularity to follow about the effects of different treatments on B elements.3. The effects on endogenous hormone contents ETH and IAA contents in theleaves was reduced after implementing heavy retractive pruning, with an increase of GA3 and ZT contents. In the critical period of bud physiological differentiation of Longan, ETH and IAA contents in leaves of trees of winter flush controlling were higher than those of trees without winter flush controlling; but GA3 content is reverse. At the same time, GA3 and ABA contents in the leaves of trees of normal pruning + winter flush controlling were lower than those of others.4. The effects on balance of endogenous hormone ABA/GA3 ratio in leaves was reduced after implementing heavy retractive pruning, while ZT/ABA and ZT/IAA ratios were increased. In the critical period of bud physiological differentiation of Longan, ZT/GA3,ZT/ABA and ABA/GA3 ratios in the leaves of trees of normal pruning+winter flush controlling with CEPA were higher than those of others, while ABA/IAA ratio is reverse; the ZT/GA3 ratio in the leaves of trees of heavy retractive pruning + winter flush controlling was higher than those of without winter flush controlling, while the ABA/IAA ratio is reverse.5. The effect of PP333 Applying PP333 after heavy retractive pruning increased the contents of N, P, K, ETH, IAA and ABA, and decreased the content of ZT and the ratios ZT/IAA,ZT/ABA in the leaves.