Effect Of GA₃ And ABA Treatment On Cellular Ultrastructure And Endogenous Hormones During Bud Secondary Burst Of Black Currant ?Ribes Nigurm L.?

Black currant?Ribes nigurm L.?is a local characteristic species of small berries,there is a huge planting area in Heilongjiang Province due to its high nutritious value.Black currant not only can be fresh eating,but also processed fruit drinks,therefore the huge market demand would be further enlarged.But the black currant in the autumn will occur the phenomenon of secondary bud.The secondary bud will not bear fruits,so this phenomenon will waste nutrition of tree,and destroy balance of tree vigour.If the temperature drop drastically will cause serious losses,even affect the industrial development.Due to treating different kind of exogenous hormone,and the water treatment wsa blank control,three black currant varieties "Yade","Bajila" and "Heifeng" used as test materials were differert on their secondary bud in this experiment.This experiment analysed the ultrastructural changes of buds and the changes of endogenous hormones?GA₃,ABA,ZT,IAA?in order to provides a scientific basis for the comprehensive disclosure of the second bud of black currant.The main findings are as follows:?1?The bud secondary burst of black currant was actually the process of breaking dormancy.The rates of bud secondary burst of three black currant varieties were different under natural conditions.We found that Yade was easy to bud secondary burst,and the rate was high to 90%.But Heifeng and Bajila were not easy to bud secondary burst.No matter the variety was easy to burst or not,it would secondary burst under the 30mg/L GA₃ treatment,and the 50ml/L ABA was on the contrary.?2?Plasmolysis was a mark of dormancy period,and it would be a reaction mechanism to protect itself.We found the phenomenon of plasmolysis of Yade has disappear when the autumn was coming.Under the natural conditions the Bajila was in the state of plasmolysis,and the plasmolysis of Heifeng would disappear later.GA₃ treatment could promote the disappearance of plasmolysis,and ABA treatment would induce three varieties of black currant to maintain the state of plasmolysis.?3?The plasmodesma was the informance and substance of bridge beyond cells.As long as the bud secondary burst,we could observed the differentiation of plasmodesma.But no differerntiation of plasmodesma could be observed,the bud would not secondary burst.So we concluded the plasmodesma was the key to black currant whether secondary burst.?4?Three varieties of black currant cells were vacuolization when the autumn was coming.Under the natural conditions,the vacuole of which variety was easy to secondary burst formed earilier.The effecct of GA₃ treatment on forming vacuole is not significant and similar to water treatment.ABA treatment could induce theelectric dense matter to exist in the vacuole of Heifeng and Bajila.?5?Starch grains were closely related to mitochondria in the process of secondary burst.The secondary burst was often accompanied with rapid decomposition of starch grains and mitochondria differentiate more mature.There were always larger volume of starch granules existing in the cells,and the number of mitochondria was less.?6?The results showed that the changes of endogenous hormones were different under different treatments by HPLC.The content of GA₃ in buds of secondary burst increased significantly under natural conditions?P < 0.05?,and IAA,ZT content maintained the same level,but ABA content had a slight decline.This indicated that GA₃ was the main promoting material for secondary germination,and the effect of the accumulation of substances during secondary burst was much greater than that of the inhibitory substances.Under GA₃ treatment,GA₃,IAA and ZT contents were significantly increased and the content of ABA decreased significantly.However,the effect of ABA treatment was on the contrary.The above results showed that GA₃,ZT and IAA were the promoting factors of bud secondary burst,and ABA were the inhibitory factors.?7?The process of secondary burst was not only a separate endogenous hormone alone play a role,the interaction between hormones can also affect the secondary burst.GA₃ and ABA were antagonistic.ZT was positively correlated with IAA,but ABA treatment could weaken the correlation.The relative content of GA₃ and ABA play a significant role in the second burst process of black currant.The analysis showed that the easy secondary burst variety Yade was more sensitive to hormone treatment.?8?The changes of endogenous hormones balance during the secondary burst process were closely related to the ultrastructure of cells.The change of ratio of?GA₃+ZT+IAA?/ABA in the secondary burst process affected the decomposition of starch granules firstly.Then it would affect the formation of large center vacuole.The formation of center vacuole was helpful to differentation of plasmodesma.