The Studies Of Flowering Time Regulation And Flowering Mechanism On ’Hass’ Avocado

The avocado（Persea americana Mill.）is a perennial evergreen fruit tree of the persea of the family Lauraceae,which is reputed‘source of life’and‘forest butter’for its high nutritional and health value and get rapidly development in recent years.Avocado is a fast-growing tree with many flowers,but the number of flowers is too large and the quality is poor,and the flowers and fruits fall seriously.Therefore,it is of great significance for improvement of fruit setting rate,by studying the flowering mechanism,regulating the flowering time and improving the quality of flowers in an appropriate way.However,the studies of flowering mechanism and flowering regulation are few and short of systematization in China.Therefore,the’Hass’avocado was used as the material to observe its flowering phenology and flower bud differentiation process in guangzhou.The relationship between flower formation and important metabolites substance was studied by comparing the differences of flower bud differentiation and metabolic substance changes under different flowering regulation techniques.The results are as follows:（1）The observation of flowering phenology of the single flower of‘Hass’avocado.‘Hass’avocado flowers are complete and perfect,but the functional male and female organs are typically temporally separated.Each flower opened and closed twice within 36hours.the first flowering happened at 6:30 on the first day,fully opened to 7:40,the blooming state continued to close at 10:30,closed completely at 12:30,the pistil matured during the stage of the first flower opening and closed,and had the ability to pollinate.The second flowering happened at 10:30 the second day,fully opened to 12:30,the blooming state began to close until 14:30 and closed completely at 16:40,and the stamens had pollination ability during the stage of the second flower opening and closed.The two blossoms overlap at 10:30-12:30.The two flowering phenomena of avocado is not only a process of pollination and fertilization,but also accompanied by the growth of filaments and petals,resulting in a significant increase in the volume of flowers after the completion of flowering.In production,pollination tree varieties can be configured accordingly.（2）The effect of Gibberellin Acid（GA₃）on the process of flower bud differentiation of terminal shoots buds.The flower bud differentiation of the avocado began in late December,and the order of the flower bud differentiation was the inflorescences of the inflorescences,the flowers and the stamens,the pistil,the whole inflorescence differentiation from top to bottom,and the top flower differentiation was the first.GA₃ treatment could promote the process of flower bud differentiation,and in the middle and late stage of this treatment（42days after treatment）,the vegetative growth of terminal bud could be initiated in advance,and the flower formation would be reversed.（3）The effect on the flowering quantity and inflorescence quality of terminal shoots treated under different treatments.The earlier the terminal shoot was treated with 100mg·L^-11 GA₃,the more obvious the effect of promoting flowering was,but the less the effect on the quality of inflorescence was.And GA₃ treatment may disrupt the environmental conditions of flower development,leading to the reversal of flower formation,from reproductive growth to vegetative growth.The earlier the basal of the terminal shoot treated with Girdling（HG）,the more obvious the effect of promoting flowers was,but the weaker the effect of controlling flower quality was.Treatment with 300 mg·L^-1 Paclobutrazol(PP₃₃₃)before anthesis（115 d）had little effect on flowering and improving flower quality,but could increase flower yield to a certain extent.（4）The changes of endogenous hormone content and ratio in the leaves of end-stage shoots under different treatments.It was found that the treatment of HG and GA₃ decreased the content of ABA and increased the contents of IAA,ZR and GA₃ in leaves,which indicated that low level ABA and high level of IAA、GA₃ or ZR could promote flower bud differentiation of avocado.The high level of GA₃ in leaves at the late stage of exogenous GA₃ treatment may be related to the reversal of flower formation in avocado.HG and GA₃treatments effectively reduced the ABA/IAA and ABA/GA₃ values of leaves,but the changes of ZR/IAA and ZR/GA₃ values were significantly different from those of CK after HG treatment,which indicated that the flowering promoting effect of HG was closely related to the values of ZR/IAA and ZR/GA_3.The changes of ZR/IAA and ZR/GA₃ values were similar to CK which showed that the flowering promoting effect of HG did not have much to do with the values of ZR/IAA and ZR/GA_3.（5）The changes of contents of total carbon and nitrogen and the ratio of C/N.It increased the contents of starch in leaves treated by HG,but the contents of soluble sugar were not obvious.GA₃ treatment reduced the content of starch,increased the content of soluble sugar in leaves.However,the early start of vegetative growth in the middle stage of differentiation may be related to the suddenly increase of soluble sugar content.The carbon content increased in the medium-term of bud differentiation（29-55d）,while the change of C/N value in the early stage of flower bud differentiation was more obvious in leaves,and the effect on the middle and later stage of differentiation was small by different treatment.