Study On Bearing Habit And Flower Development Of Acer Truncatum

Acer truncatum Bunge has high economic value.A.truncatum seeds contain up to 47%oil,and A.truncatum seed oil contains more than 4.6%nervonic acid.It is one of the few nervonic acid resource plants in nature.However,at present,the fruit yield of A.truncatum fruit is low,the flower sex is complex,the proportion of female flower is low.There is still a lack of cultivation and management measures to improve fruit yield and quality.This study studied the fruiting characteristics,gender system,flower bud differentiation and flowering process,the effect of exogenous growth regulators on sex proportion of flowers and gene regulation network in the process of flowering,so as to provide a theoretical basis for cultivation and management measures such as plastic pruning and flowering regulation of A.truncatum.The main conclusions are as follows:A.truncatum has the characteristics of strong bearing shoots,and the fruiting parts include short branch top buds and long branch side buds.The fruiting branch group is Y-shaped,which is formed by the development of bearing shoots and laterl shoots,and then forms the continuous fruiting ability for many years.The yield of bearing shoot was positively correlated with the top and basal diameter of parent shoot and bearing shoot,but not with the length of parent shoot.The parent shoot with top diameter greater than 3.08 mm and planted on the side of vegetative branches were better in yield,fruit number and seed weight.The flowers of A.truncatum can be divided into functional female flowers and functional male flowers.Stamens and pistil are available in functional female flowers,the anthers of functional female flower did not crack,and functional female flower only had female function.There were two types of functional male flowers:type I and type II.The anther of both two types of functional male flowers could produce mature pollen and crack.The functional male flowers only had male function.A.truncatum was a rare tree species of duodichogamy,and there were two mating systems:protandrous and protogynous type.The order of floret opening of protandrous type is functional male flowers–functional female flowers-functional flower male flowers,and the order of floret opening of protogynous type is functional female flowers-functional male flowers-functional male flowers.The morphological differentiation of flower bud began in early July,the differentiation of inflorescence and floret began in early August,the differentiation of stamen and pistil began in late August,and the development of female gametophyte was later than that of male gametophyte.The key period of flower sex differentiation of Acer truncatum is from late March to early April in the following year.Endogenous GA₃,the ratio of endogenous GA₃ to other hormones might be related to flower sex determination.The number and proportion of functional female flowers in 100 mg/L and 200 mg/L concentrations were significantly higher than those in the control group.1%and 2%sucrose solution increased the proportion of functional female flowers.Endogenous GA₃ at the critical stage of flower sex differentiation increased significantly in the four treatment groups that increased the proportion of female flowers compared with the control group,（GA₃+IAA）/ABA ratio increased significantly,while ZT/GA₃ratio decreased significantly.In this study,15 c DNA libraries were constructed from samples from three periods,and a total of35249 genes were obtained,including 7506 new genes.8066 different expressed genes（DEGs）were screened in the early stage of flower development and 705 differential genes were screened in the late stage of flower development,of which 20 DEGs were directly related to flower development.Under gibberellin spraying treatment,only 8 DEGs were screened in the early stage and 764 DEGs were screened in the later stage,of which 10 were directly related to flower development,including LFY,AP3,PI,AG,SEP2,SEP3,CRC,etc.among other transcription factors,TGA9,TGA10,STM,etc.