Study On Mechanism Of GA₃、GA₄ Regulating Dormancy Release Of Peach Bud

Dormancy is a biological adaptation of plants to resist adverse environment.Deciduous fruit trees can survive the cold winter better only after normal deciduous and dormancy,the dormancy of buds in winter will directly affect the growth and fruiting in the next year.Temperature drop is an important condition for fruit trees to enter winter dormancy and meet the low temperature demand.At present,the phenomenon of "warm winter" brought by global warming has begun to affect low temperature accumulation in some areas,thus affecting the normal dormancy and dormancy release of fruit buds.It was found that gibberellin plays an important role in the process of dormancy release,and its regulatory network needs to be perfected.In this experiment,the peach variety ’Chunjie’ was used as the research material,and the effect of active gibberellin(GA3,GA4)on the dormancy release of the variety was taken as the entry point,and a series of physiological and biochemical changes occurred in the bud were detected after exogenous treatment,so as to explore the mechanism and pathway of gibberellin in the process of dormancy release,which provided a theoretical basis for chemical control of sleep break and regulation of maturity stage.The main findings are as follows:1.During dormancy process,GA synthesis and metabolic enzymes of flower buds and leaf buds of ’Chunjie’ are different and similar.In the dormant period,the activity of GA synthetase GA20 oxidase in flower buds was significantly higher than that in leaf buds,with the highest difference of 73.74 U/L.In the dormancy release period,the activities of GA synthetase GA20 oxidase and GA3 oxidase increased significantly in flower and leaf buds.In the dormancy release stage on November 15,the activity of GA2 oxidase,a GA-breaking enzyme,decreased significantly in both flower and leaf buds.2.During dormancy,GA synthesis and metabolism genes of flower buds and leaf buds of ’Chunjie’ were different.The expression levels of GA synthesis gene Pp CPS,Pp KS,Pp KAO and Pp GA20ox1 in flower buds were significantly higher than those in leaf buds,while the expression of GA decomposition gene Pp GA2ox2 was significantly lower than that in leaf buds,indicating that flower buds could accumulate more active GAs and thus release dormancy earlier.3.Both 0.5mmol/L GA3 and GA4 treatments could promote the release of dormancy of’Chunjie’ flower buds,and the germination rate after GA4 treatment(60%)was 8 percentage points higher than that after GA3 treatment(52%).After GA3 and GA4 treatments,GA20 oxidase,GA3 oxidase and GA2 oxidase were involved in the feedback regulation.In the dormancy release period,the activities of GA20 oxidase and GA3 oxidase of GA synthetase were increased after 48 h of GA3 and GA4 treatments,and the increase of the activities of GA20 oxidase and GA3 oxidase(GA synthetase)under GA4 treatment was significantly higher than that under GA3 treatment.GA3 treatment inhibited the activity of GA2 oxidase(GA decomposing enzyme)for 48 h,and GA4 treatment inhibited the activity of GA2 oxidase for 24 h.4.GA3 treatment significantly induced the expression of GA synthetic genes Pp GA20ox1 and Pp GA20ox3 at 48 h and GA4 treatment significantly induced the expression of GA synthetic genes Pp KAO,Pp GA20ox2 and Pp GA20ox3 at 24 h during the dormancy release stage in the flower buds of ’Spring Blue’.Both GA3 and GA4 treatments could inhibit the expression of Pp GA2ox2,but GA4 treatment could inhibit the expression of Pp GA2ox2 24 h earlier than GA3 treatment.