Study On Anatomy And Hormone Regulation On Sex Differentiation In Castanea Henryi

Castanea henryi is an important woody grain plant in the south of China.As a result of large amount of male flowers but few female flowers,the yield of C henryi is low and unstable.Therefore,the flower bud differentiation rules of C henryi and the effects of phytohormone on flower sex differentiation were systematically studied using C.henryi 'Huali 2' as experimental material,through the methods of paraffin section technique,ELISA analysis technology and other methods,so as to provide a theoretical basis for improving yield.The main results are described as follows:1.The rules of flower bud differentiation and the key period of floral sex differentiation of C.henryi was determined.The post-winter inflorescence of C.henryi and its three gender types(female flower,male flower and hermaphrodite flower)were studied by paraffin section.The results showed that post-winter inflorescence primordium appeared at the end of March and exposed in the middle of April.The female and male flowers could be identified in the late April,and the female flowers flowered in the middle of May,while the male and hermaphrodite flowers in the late May.In the post-winter inflorescence,the differentiation time of the three types of flower sex was from April to May.All flowers went through a bisexual stage in the initial stage of their differentiation,and there were female and male organ primordium at the beginning of development,and then the female,male or hermaphrodite flowers were exhibited in response to selective induction or abortion of the sex organ primordium.The key period of sex differentiation of C.henryi is post-winter inflorescence primordium differentiation phase and pistil primordium differentiation phase,the end of March and the end of April,respectively,are the key period of sex differentiation of C.henryi,in which the number of mixed inflorescences or the number of male and female flowers on the mixed inflorescence can be changed through exogenous hormone treatment,in order to control the gender ratio of flower.2.The effects of exogenous hormone spraying on sex ratio of C henryi were clarified.Before the emergence of post-winter inflorescence,250 mg/L 6-BA and 400 mg/L GA3 were sprayed on the flower buds of C.henryi(with water spray as a control).The results showed that 6-BA remarkably increased the number of female flowers and post-winter inflorescences and the consequent ratio of female flowers to male flowers,whereas had no significant effectiveness on the number and length of male flowers,which indicated that 6-BA could promote female flower differentiation.While GA3 significantly increased the length of male inflorescence and the number of hermaphroditic flowers,indicating that GA3 was beneficial to the differentiation and elongation of stamens.3.The effects of exogenous hormones on the contents of endogenous hormones in the differentiation of female and male flowers of C.henryi were explored.The contents of endogenous hormones(ZT,GA3,GA4,IAA,ABA and SA)in flowers in the critical period of female and male flower differentiation of C.henryi were analyzed by ELISA,which were collected from the chestnut trees treated with exogenous 6-BA and GA3.The results showed that in the key period of sex differentiation,the contents of IAA and SA in male flowers under the three treatments were higher than that in female flowers,indicating that the higher IAA and SA contents were beneficial to the formation of male flowers.After GA3 treatment,the endogenous GA3 contents in male flowers were significantly higher than that in female flowers,indicating that the higher GA3 contents were beneficial to the differentiation and elongation of stamens.The ZT contents and(GA3+ZT)/(IAA+ABA)value of female flowers treated with 6-BA were significantly higher than those of male flowers,indicating that higher ZT contents and(GA3+ZT)/(IAA+ABA)values are beneficial to female flower differentiation.After 6-BA treatment,the ABA contents of female flowers were significantly lower than that of CK and GA3 treatments,and the ABA contents of female flowers were significantly lower than that of male flowers,indicating that low levels of ABA are beneficial for female flower differentiation.Exogenous 6-BA and GA3 could regulate the sex differentiation of C.henryi by changing the contents of ZT,GA3,ABA and the values of(GA3+ZT)/(IAA+ABA),and then change the ratio of female to male flowers.