The Research On Flowering Characteristics Of Five Species Of Cerasus

Cerasus plants bloom in early spring every year,most of which are bloom before or at leaf unfolding,and are important landscape trees in the world due to the highly ornamental flowers in rich colors.In this study,Cerasus discoidea,Cerasus dielsiana,Cerasus campanulata,Cerasus conradinae and Cerasus yunnanensis introduced in Hunan Forest Botanical Garden were used to investigate the phenological phase of flowering,and therein to compare the morphological and structural characteristics of flower organs,and to study the physiological and biochemical changes in flowering.The main research results were as follows:The five flowering phenological period of Cerasus plants can be divided into flower bud recovery period,bud scale dehiscence period,pedicel extension period,initial flowering period,full flowering period,falling flowering period and fruit setting period.Among them,the flower organs grow rapidly during the flower bud recovery period to pedicel extension period.The flowering period of Cerasus lasted from early February to mid-March.The flowering period and the flowering period of Cerasus discoidea was the earliest and the shortest respectively,the Cerasus campanulata was later flowering but with the longest flowering period,and the flowering period of Cerasus yunnanensis and Cerasus dielsiana was the latest.In terms of flowering period,Cerasus discoidea had the shortest flowering period and Cerasus campanulata had the longest flowering period.The crown diameter of Cerasus dielsiana flower was the largest and that of Cerasus campanulata flower was the smallest.The Cerasus campanulata was the most colorful crimson,while the Cerasus conradinae was the lightest white.Significant growth of floral organs occurs from floral bud recovery stage to pedicel extension stage.Principal component analysis showed that the total cumulative contribution rate of 10 flower organ traits to flowering characteristics reached 84.712%,and the flowering characteristics of Cerasus campanulata were the best.The results of correlation analysis showed that the size and character index of flower had the greatest influence on flowering characteristics.According to the time series cluster analysis,the five species of Cerasus can be divided into three time series groups:early flowering stage（Cerasus discoidea,Cerasus campanulata）,middle flowering stage（Cerasus conradinae）,and late flowering stage（Cerasus dielsiana,Cerasus yunnanensis）.The results of staining test showed that the pollen germination rates of Cerasus campanulata and Cerasus discoidea were significantly different（P<0.05）.The results of in vitro culture of pollen showed that there were significant differences in pollen germination rates among the five species（P<0.05）.The germination rates ranged from high to low were shown as:Cerasus campanulate,Cerasus discoidea,Cerasus conradinae,Cerasus yunnanensis and Cerasus dielsiana.The observation and analysis of scanning electron microscopy showed that the pollen morphology of the five species of Cerasus was similar,and all of them were nearly oval or long spherical.Correlation analysis showed that there was a significant positive relationship between pollen germination rate and red axis value and polar axis value（P<0.05）.The higher the germination rate,the lower the fruit drop rate.However,there was no significant relationship between fruit drop rate and red pole ratio.Studies on different storage temperatures showed that the germination rate of pollen decreased rapidly under normal temperature,but decreased slowly under low temperature.The low temperature of-60℃ was more suitable for long-term storage of pollen of Cerasus plants.The results showed that the flowering phenological period of five Cerasus species were closely related to the changes of soluble sugar,soluble starch,soluble protein,SOD and POD activities.Among them,the change curve of soluble sugar content of five Cerasus species was a bimodal curve with a slight increase in the overall trend.The variation curve of soluble starch content was stable except Cerasus discoidea with the higher change in the full flowering period.The change curve of soluble protein content was a bimodal curve with the overall trend rising,basically.The activity of SOD in five species fluctuated before the full flowering stage,while it was decreased gradually after the full flowering stage.Cerasus conradinae showed a unimodal curve,while the other 4 species showed a bimodal curve.The activity curve of POD was bimodal curve.The content of IAA in Cerasus campanulata showed a smooth change curve,except its full flowering period with obvious changes,while the other 4 kinds of IAA showed relatively stable changes,while the ABA content of Cerasus dielsiana was shown a higher trend.The content of GA₃ in Cerasus conradinae changed greatly during the floral organ phenology,while other indicators changed slowly.The result of correlation analysis indicated that there was a significant correlation between nutrient contents,enzyme activities,endogenous hormones levels,pollen characteristics and flowering morphological indexes of five species of Cerasus（P<0.05）.R cluster analysis showed that most flowering traits had independent characteristics,but there was a significant relationship among the changes of physiological and biochemical indexes and the flower size,flower charactericstics and the flower amount at flowering stage.