Effects Of Exogenous Melatonin On Flower Bud Differentiation And Bolting Of Radish(Raphanus Sativus L.)

Radish?Raphanus sativus L.?is an important vegetable crop.During the cultivation of Radish,the yield and quality of radish are often caused by low temperature and long sunshine,which leads to moss extraction,flowering,succulent root bran and ultimately loss of commodity.Therefore,it is very important to study the effect of low temperature on the physiological characteristics of radish seedlings and regulate the new way of flower bud differentiation and moss extraction for the industrial development.Melatonin(N-acetyl-5-methoxytryptamine?MT?is a tryptophan indoles derivative that has the functions of regulating plant growth and development and responding to abiotic or biological stresses.At present,there are limited studies on the effect of MT on flower bud differentiation and moss-pulling,and its regulatory mechanism remains to be further studied.In particular,the effect of MT on the regulation of endogenous hormone changes and the spatio-temporal expression of flowering genes in the process of flower bud differentiation and moss-pulling remains unclear.Based on two significant sexual differences in winter turnip varieties'Korean big root'?bolting resistance?and the'New Zealand short leaf number13?easy bolting?as materials,set up MT approach and concentration,using the plant tissue section microscopy techniques,plant physiology and molecular biology research techniques from morphology,seedling resistance to cold physiological,the changes of endogenous hormones and flowering gene expression of space and time of MT system is studied on the effects of radish bud differentiation and bolting.The main results are as follows:1.Before exogenous MT application,radish bolting,flowering regular observation:according to the observation of radish morphological changes in the process of reproductive growth appearance,the reproductive stage can be divided into flower bud undifferentiated stage,bud differentiation stage,budding stage and bolting stage,flowering stage,five phases,budding stage of radish bud buds grow slowly,can be observed from bolting stage to flowering stage can be observed when the stamen and pistil development process.By means of shoots and flowers are organized in different stages of the above structural observation,reproductive stage of radish can be subdivided into bud undifferentiated stage,the early stage of the flower bud differentiation,flower primordium differentiation stage,sepal primordium differentiation stage,petal primordium differentiation stage,stamen primordium differentiation stage and pistil primordium differentiation stage,pollen formation,ovary enlargement stage such as nine times.2.The influence of exogenous MT on the moss-pulling traits of radish:moss-pulling radish cultivar'Korea big root'blossomed later than moss-pulling radish cultivar'New Zealand Short Leaf no.13'.The extraction time of both cultivars was delayed after MT with gradient concentration?50?M,100?M,200?M,500?M,1000?M?,and the delay time was prolonged with the increase of application concentration.The inhibitory effect of exogenous MT on radish moss extraction was more obvious than that of leaf application,among which500 M MT had the most obvious inhibitory effect on flower bud differentiation and moss extraction of radish.3.In the four key stages of reproductive growth of radish flower buds,namely,the undifferentiated stage,the budding stage,the mossy stage and the flowering stage,the exogenous root application of melatonin with 500?mol/L could increase the soluble sugar and soluble protein content in the flower bud differentiation and mossy process.By increasing the content of endogenous MT and decreasing the content of GA₃,IAA,ABA and ZT,the differentiation of flower buds and the process of bolting were slowed down.In addition,the application of 500?M melatonin to exogenous roots significantly increased the spatio-temporal expression levels of FLC and its alleles FLC1.1 and FLC1.2?SVP,and decreased the spatio-temporal expression levels of vernalization genes VRN1 and VRN2,as well as the flowering promoting gene SOC1 and LEY,so as to slow down the process of turnip flower bud differentiation and mossy extraction.4.Study on alleviating chilling stress of radish seedling by exogenous MT:applying 500?M exogenous root under low temperature MT can maintain the thickness of leaf epidermis,the compactness of palisade tissue,the size of sponge tissue cells;improve photosynthetic indexes such as net photosynthetic rate,stomatal conductance,intercellular CO₂concentration,transpiration rate;improve antioxidant enzyme activities such as SOD,pod,cat,APX;increase proline content;significantly reduce MDA content,relative conductivity,H₂O₂Content,superoxide anion content,etc.,so as to To alleviate the oxidative damage of radish seedlings by low temperature treatment.5.These results provided the theoretical reference for the chemical regulation of flower bud differentiation and bolting in radish production,and had certain practical application value.