Response Mechanism Of Camellia Oleifera Floral Organ Development To Adverse Circumstances And Regulation Technique Of Plant Growth Regulator

Camellia oleifera Abel.is a woody oil tree special to southern China,which benefits economically,ecologically and socially.The C.oleifera industry is developing rapidly in China.Newly planted forest and upgraded low yield forest are increasing year by year.So the inter-regional introduction of C.oleifera varieties is inevitable.As a non-wood forest species with flowering in autumn or winter,insect pollination and self incompatibility,flowering time is an important factor in the introduction of C.oleifera.It is found that the flower buds of C.oleifera are sensitive to the environment.Heat and drought lead to a significant delay in the flowering season and affect the flower quality.Therefore,on the basis of systematic evaluation of the adaptability of 10C.oleifera varieties,the response mechanism of floral organ development of C.oleifera to adverse circumstances was studied with 'Changdetiechengyihao'.The regulatory effect of plant growth regulator on floral organ development was also explored.The purpose of this study is to lay a theoretical foundation for the introduction and reproductive growth regulation of C.oleifera.The main results are as follows.(1)Evaluation on the adaptability of 10 C.oleifera varieties.The physiological indexes of cold tolerance and drought tolerance of Camellia oleifera were determined by indoor gradient low temperature stress and field natural drought stress.The flowering time,leaf structure,leaf growth potential and pollen indexes of Camellia oleifera were obtained by field observation,paraffin section and physiological experiment.The 46 specific indexes of the above 5 categories(stress tolerance,flowering time,leaf structure,leaf growth potential and pollen)were correlation analyzed to select the representative indexes to evaluate the adaptability of 10 Camellia oleifera varieties in Wuhan by fuzzy comprehensive evaluation method.The results showed that,among the 46 specific indexes,11 indexes were representative,such as flowering time,cold tolerance,drought tolerance,CTR,SR and so on.The order of adaptability of 10 Camellia oleifera varieties in Wuhan was:'Changlin18hao' 'XLC25' 'Changdetiecheng yihao' 'Eyou465' 'Ganzhouyou8hao''XLC10' 'Changlin4hao' ' Ganhozuyou6hao' ' QY235' and 'Changlin3hao'.(2)Morphological and physiological studies on the floral organ development of C.oleifera under stress.To locate the key period of flower organ development of'Changdetiechengyihao' responses to adverse circumstances,the process of flower bud differentiation in 2018,a normal year and 2019,a heat and drought year was compared by microscopic observation,and the physiological changes in the process were also analyzed.The results showed that,the growth stagnation began to appear in 2019 at the stamen and pistil formation stage,and the stagnation degree reduction at the ovary and anther formation stage,and the growth began to resume at the stamen and pistil maturity stage.The water content,carbohydrate content,antioxidant enzyme activity and hormones content of flower buds of 'Changdetiechengyihao' also changed along with the flower bud growth process under stress.(3)Transcriptomic analyses of C.oleifera on floral organ development under stress.The stress response mechanism of floral organ development of C.oleifera was explored by transcriptomic analyses of four flower buds stage(young anther stage,microsporocyte formation stage,microsporocyte meiosis stage and pollen maturation stage).The results show that,162,621 unigenes were assembled from the four flower buds stages of 'Changdetiechengyihao',with an average length of 795.78 bp,N50 length of 972 bp and GC content of 37.67%.Among the differential expressed genes,the expression levels of growth rate(CYC,EXP),material and energy metabolism(PIP,G6PDH),stress response(HSP,WRKY)and hormone metabolism(GA20ox,GID1,NCED,SNRK2),which are dormancy related biological regulation process genes are changed in certain rule.Further analysis of other dormancy related genes,such as MADS-box gene SVP,flowering pathway(VRN,VIN,COL,ELF)and flowering integration factors(FLC,SOC),all showed that the growth stagnation and dormancy type of 'Changdetiechengyihao' was between internal dormancy and ecological dormancy.During the period of flower bud stagnation,genes related to pollen sterility,such as DYT,BHLH10 and SERL1/2,were expressed in large quantities.It is speculated that adaptive growth of 'Chang detiechengyihao' is an evolutionary strategy to ensure normal reproductive growth.(4)Study on the effect of plant growth regulator on the floral organ development of C.oleifera.Plant growth regulator was applied in different stages of floral organ development of C.oleifera to explore the regulation effect on flower organ development of C.oleifera under stress.The results showed that,when treated with 400 mg·L-1 of gibberellin,the tree flowered earliest and the flowering period was concentrated.While,when treated with 150 mg·L-1 of abscisic acid,the effect was opposite.The pollen viability was iuproved when treated with 200 mg·L-1 of auxin and 150 mg·L-1 of abscisic acid.The number of anthers and the size of flower organs were increased when treated with 400 mg·L-1 of gibberellin and 200 mg·L-1 of auxin.Gibberellin and auxin can significantly increase the content of soluble sugar in flower bud and reduce the content of starch.Abscisic acid had the opposite effect.Gibberellin could increase the content of endogenous gibberellin and auxin,and reduce the content of abscisic acid,and auxin had the same effect.Abscisic acid could increase the content of endogenous abscisic acid,but also reduce the content of endogenous gibberellin and auxin.In accordance with the changes of endogenous plant hormones,GA20ox expression increased and GAI decreased when treated with gibberellin and auxin.Abscisic acid inhibited the expression of and promoted the expression of gene NCED and ABF.The expression levels of FLC and PHYA in flower buds treated with gibberellin and auxin decreased significantly,while the expression levels of FLC and PHYA in flower buds decreased slowly when treated with abscisic acid.To sum up,the stress response of floral organ development of C.oleifera happened from the stamen formation stage to the stamen maturity stage.In the response mechanism,cell growth,material and energy metabolism,stress resistance reaction,hormones regulation and other biological regulation processes related to dormancy were included.In the mechanism,plant hormones were important regulatory substances.Gibberellin,abscisic acid and auxin could regulate the flowering time and the flower style of 'Changdetiechengyihao'.When treated with plant growth regulator,the content of carbohydrate,hormones and the gene expression changed along with the floral organs development process under stress.