Study On Flower Bud Differentiation And The Relationship With Endogenous Hormones In Xanthoceras Sorbifolium Bunge

Xanthoceras sorbifolium Bunge is a monoecious plant with different flowers.The number of male flowers is much higher than that of female flowers,which is an important factor leading to the low seed yield finally,which seriously restricts its development.This experiment took the 8-year-old Xanthoceras sorbifolium Bunge in Shengda Forest Farm of Shandong Province as experimental materials.Through the external morphology observation,combined with the paraffin section and meteorological data observation,the relationship of external morphology,internal anatomical structure of flower bud,and meteorological factor during the flower bud differentiation process was analyzed.To study the relationship between hormones content and flower bud differentiation in Xanthoceras sorbifolium Bunge,four kinds of endogenous hormones in female flowers and male flowers were determined by HPLC.On the basis of determining the critical period of gender differentiation,the spraying of the plant growth regulators 6-BA and GA3 was carried out.The study can provide a basis for timely sampling of flower bud differentiation and implementation of gender regulation technology in Xanthoceras sorbifolium Bunge.The main results were as follows:(1)The flower buds of Xanthoceras sorbifolium Bunge of the year bloomed from the formation of flower buds at the end of May to the middle of April of the following year,which lasted about 11 months.Both female and male flower can be gendered in the early stage of sex differentiation,and there is no difference in morphological structure.When the>K(biological zero point)effective accumulated temperature reached 1402.4℃,the flower buds began to differentiate and the flower primordium appeared,at which time the average temperature was 30℃.When the>K effective accumulated temperature reached 1854.7℃,the basal primordium differentiated.When the ≥K effective accumulated temperature reached 2808.4℃,the petal primordium and stamen primordium appeared,and the average temperature was 27.58℃.At the beginning of March of the following year,when the ≥K effective accumulated temperature reached 20.2℃,the pistil primordium began to differentiate,and the average temperature was 8℃.During flower bud differentiation,there is a time-series correspondence between internal structure and external morphology.(2)The difference between male and female flowers appeared when male and female gametophytes were formed.Megaspore mother cell division stopped during the tetrad stage in male flowers.The corresponding external appearance of the buds was green,with a transverse diameter of 2.05～4.54 mm and a longitudinal diameter of 2.99-5.32 mm.The>K effective accumulated temperature was 230.6℃.Mononuclear pollen grains of female flowers showed vacuolization decline during mitosis stage,with flower bud’s transverse diameter of 12.25～18.3 mm and longitudinal diameter of 8.3～10.98 mm.The≥K effective accumulated temperature was 264℃.As a result,the abnormal development of sexual organs caused the formation of unisexual flower.(3)The ZT content increased gradually during the stage from flower bud undifferentiated period to pistil differentiation period.During male and female gametophyte formation period,the ZT content of female flowers was always higher than that of male flowers.The IAA and ABA content of female flowers were significantly higher than that of male flowers when the stamens of female flowers developed abnormally,and the GA content was significantly lower than that of male flowers.High level of ZT can promote flower bud differentiation,and was beneficial to the development of female flowers.High levels of IAA and ABA had a promoting effect on female flowers formation,and high level of GA promoted the development of male flowers.(4)The ratios of ABA/IAA,ABA/GA and ZT/GA were at a high level during the period from flower bud undifferentiated period to pistil differentiation period.When male flower pistil dysplasia was abnormal,the ratios of ABA/IAA and ZT/IAA of male flower were significantly higher than that in females,indicating that high levels of ABA/IAA,ABA/GA and ZT/GA were beneficial to flower bud differentiation;and high levels of ABA/IAA and ZT/IAA were beneficial to stamen development.(5)Spraying 6-BA can increase the proportion of female flowers in the top inflorescence before the female and male flower can be sexually differentiated,and the best effect is 160g/L 6-BA treatment,which is 4.24%.Spraying 150 mg/L GA3 increased the fruit setting rate by 16.8%.Both 6-BA and GA3 treatments significantly promoted the protein content in the top inflorescence.The best results were 320 mg/L 6-BA and 100 mg/L GA3.The treatment of 160 mg/L 6-BA was the most effective in increasing the fruit volume.The treatment of 240 mg/L 6-BA had the best effect on fruit weight,peel thickness and peel weight,which increased by 26.79%,16.53%and 39.15%,respectively;160mg/L 6-BA treatment had the highest seed weight and the highest seed yield,which increased by 33.92%and 20.79%,respectively.From the perspective of seed quality,160 mg/L of 6-BA treatment was the best.