The Effects Of Plant Growth Regulators On Preharvest Fruit Drop Of A4Seedless Litchi And Their Regulation Mechanism

Taken10-years-old trees of A4seedless Litchi as material and spraying dif-ferent plant growth regulators (NAA, GA3, CPPU and ZR) on25and30days before harvest to explore the effects of different regulator on preharvest fruit dr-op and the regulation of fruit drop mechanism.The results are as follows:1. Effects of different concentrations of different plant growth regulator on Preharvest Drop of A4Seedless Litchi:The results showed that different pla-nt growth regulators could prevent the drop of litchi fruits before harvest.In di-fferent treatments,40mg/L NAA could reduce preharvest fruit drop rate remar-kably;20mg/L GA3could reduce preharvest fruit-drop rate very well;40mg/L CPPU could reduce preharvest fruit drop rate in utter most; and2mg/L Z-R could also have a good effect on reducing preharvest fruit drop rate.Effects of different growth regulator treatment on A4Seedless Litchi fruits drop rate:40mg/L NAA<40mg/L CPPU<20mg/L GA3<2mg/L ZR<CK.2. Effects of different concentrations of different plant growth regulator on A4Seedless Litchi Fruit quality:In different treatments,40mg/L NAA could re-duce fruit titratable acidity content, as well as improve single fruit size and w eight remarkably;20mg/L GA3could reduce titratable acidity content of fruit f-lesh, and increase single fruit weight;40mg/L CPPU could also reduce the fruit titratable acidity content,and increase the weight of single fruit;0.5mg/L ZR c-ould increase the diameter and improved fruit weight very well.3. Effects of different concentrations of different plant growth regulators on A4Seedless Litchi Fruit quality and character:The results showed that NAA, GA3,CPPU, ZR treatments in peduncle could effective reduce the formation of fruit stalk abscission layer through increasing endogenous CTK, GA,(IAA+GA+CTK)/ABA,and slow down the decline of IAA contents and the rise in ABA content; The declining trend in peel endogenous GA and CTK were slowed do-wn by spraying NAA and also slowed the decline of endogenous GA by spra-ying CPPU; The effective treatment was achieved on the stone, which could i-mprove the content of ABA and promote the decrease of GA content by spray-ing NAA, and could improve the ABA and CTK content, and promote the dec rease of GA content by spraying GA3, and also could increase the content of CTK by spraying CPPU and ZR.The results indicated that a combination of enhancing inner peduncle tissu-e endogenous CTK, GA and delaying the decrease of IAA and increase the co-ntent of ABA by spraying plant growth regulator in preharvest, causing (GA+IAA+CTK)/ABA ratio increased, which is probably the main reason why preharvest fruit drop rate decreased.