Study On The Relationship Between Multiple Flowering And Endogenous Hormones In Blueberries

Blueberry,well known as bilberry,belongs to the plants of the genus Ericaceae（Vaccinium）,and is evergreen shrub,with higher nutritional value and health value.Most blueberries blossom and harvest once per year,and a few varieties have the characteristic of flowering and fruiting twice a year,while most southern highbush blueberry varieties planted in Yunnan have the special phenomenon of blooming and bearing fruit multiple times a year.Therefore,in order to reveal the formation mechanism of multi-flowering phenomenon,morphological formation,and physiological and biochemical process during the multi-flowering flower bud differentiation,and then provide theoretical basis for the production of the regulation of flower and fruit,in this present paper,we observed the phenological period of the different blueberry varieties,studied the flowering habits of blueberries,applied paraffin section technique to explore the morphogenesis of blueberry flower bud differentiation,adopted selective reaction/multiple reaction monitoring technology（SRM/MRM）to investigate the changes of hormone content during multiple flowering of blueberry,and discussed the relationship between multiple flowering and endogenous hormones of blueberry from the aspects of morphology,anatomy and physiology.Specific results are as follows:1.The phenological observation of the three tested varieties showed that the northern highbush blueberry‘Bluecrop’had flowers and fruits once a year,northern high bush blueberry‘Sweetheart’with 15%gene of northern highbush had two flowers and two fruits a year,and southern high bush blueberry‘Sharpblue’had three flowers and three fruits a year,which is very rarely reported in domestic and international varieties and worthy of further discussion.2.By observing the phenological period of the three tested varieties,it was found that there was an obvious time interval between the end of fruit ripening of‘Sweetheart（1st time）’and the budding period of’‘Sweetheart（2nd time）’.However,there were different degrees of overlap between（1st time）and（2nd time）,and between（2nd time）and（3rd time）in terms of‘Sharpblue’.3.The differentiation of blueberry flower bud had six stages,including initial,inflorescence primo,sepal primordium,petal primordium,stamen primordium and carpel primordium.The carpel differentiation stage could be divided into three terms,the early,middle and late stage.The flower bud differentiation period of‘Bluecrop’was from July3 to August 25,‘Sweetheart（1st time）’was from March 23 to May 11,‘Sweetheart（2nd time）’was from July 6 to August 25,‘Sharpblue（1st time）’was from May 4 to June 16’,‘Sharpblue（2nd time）’was from July 28 to September 7,and‘Sharpblue（3rd time）’was from September 25 to November 9.The results displayed that there were differences in flower bud differentiation among different varieties and multiple flowering.4.At any period of three processes of flower bud differentiation of Sharpblue,the content of ABA was significantly higher than those of Gas,ETH,CKs and IAA.During the first process of flower bud differentiation,the content of ABA was higher than those of GAs,CKs,IAA and ETH.From the beginning to the end of differentiation,the content of ETH remained a gentle level without an obvious fluctuation.The content of IAA was firstly declined and then elevated from the early stage of flower bud differentiation to the stamen differentiation stage.The dynamic change of CKs content was quite opposite to that of IAA,presenting an antagonistic relation during the whole process of flower bud differentiation.Content change of GAs was similar to that of CKs in a relatively low level.During the second process of flower bud differentiation,the content of ABA was in an increased trend,while that of ETH maintained stable.From the undifferentiated stage to inflorescence primordium differentiation phase,relative contents of ethylene,cytokinin,gibberellin slowly increased and then gradually decreased to the baseline levels.At the third process of flower bud differentiation of Sharpblue,the content of ABA exerted a declined trend.The content of ETH maintained stable.A slow increase was observed in contents of CKs and GAs.The content of IAA increased at inflorescence primordium differentiation phase,and then declined after the petal primordium differentiation phase.5.Dynamic changes of five types of hormones vary a lot in different phase during the process of flower bud differentiation.The content of ABA presented an overall declined trend at the first and third process of flower bud differentiation,which was elevated at the second process.The content of GAs was elevated first and then declined both at the first and second process.It was slowly elevated at the third process.At the first process of flower bud differentiation,the content of IAA was initially declined and then elevated until the petal primordium differentiation phase,which was declined to the end.At the second process,it immediately increased and sharply decreased to a relatively low level.The content of IAA increased at the inflorescence primordium differentiation phase of the third process,followed by a decline after petal primordium differentiation phase.The content of CKs increased first and decreased until the petal primordium differentiation phase,followed by a slow increase at the first process.It increased until inflorescence primordium differentiation phase,and then declined at the second process.During the third process,the content of CKs remained a low level.At the first process of flower bud differentiation,the content of ETH presented an overall elevated trend at the first and third process of flower bud differentiation,which was declined at the second process.6.This study proved that different types of CK_S in blueberries had different trends:tz R,i PR and cz R had different dynamic changes,while TZ and CZ were in a parallel state.Different kinds of gibberellins had different effects on flower bud differentiation.GA₁and GA₂₀,and GA₈ and GA₂₀ had different dynamic changes,and four gibberellins had an interactive regulating effect on the dynamic changes of blueberry bud formation stage in spring shoot.The above results revealed that higher concentration of ABA and a certain level of GAs were needed during the flower bud formation of blueberry,and lower concentration of IAA was needed during flower bud formation.Regardless of the season,the flower bud differentiation can form higher concentration of ABA,which is the key for the southern highbush blueberry“Sharpblue”to form multiple flowering in Dali,Yunnan province.