Analysis Of ⁶⁰Co-? Radiation Mutagenesis On Two Species In Bauhinia And Phenotypic Diversity Of Related Species In Bauhinia

Bauhinia variegata,Bauhinia purpurea and Bauhinia blakeana were the famous ornamental of Caesalpiniaceae,which were widely used in urban landscape.We based on the preliminary results of our task group,induced the seeds of Bauhinia variegata and Bauhinia purpurea in different ⁶⁰Co-?radiation dose?175?200?225?250?275Gy?,further explored seed germination,aberrations of radicle nucleus and chromosomal,morphological observations,biomass,photosynthetic effects and major physiological characteristics of M1,we also observed growth of M1 to select mutant plants comprehensively,which could provide basic data and theoretical support for the cultivation test and variety breeding.Simultaneously,phenotypic variations between populations as well as phylogenetic relationship by investigating and analyzing the 10 cultivated populations of three species in Bauhinia from universities or parks in Guangzhou,which could provide theoretical support for the selection and breeding of fine varieties of Bauhinia in future.The major results were as follows:?1?Effects of radiation on root-tip cells of Bauhinia variegata showed that:Both nucleus aberration ratio and chromosome aberration ratio tended to increase with the increasing of radiation dose,the type of nucleus distortion was mainly micronucleus,the largest total micronucleus ratio was 275Gy,which was 14.38 times than control group.Chromosome aberration type was mainly chromosome bridge,chromosome fragment,and backward chromosome,the largest ratio was 275Gy as well,up to 14.11%.?2?Effects of radiation on the germination,growth of Bauhinia variegataand and flowering traits of Bauhinia purpurea showed that:The germination rate,germination potential,germination index,emergence ratio and seedling ratio were decreased with the increase of irradiation dose.The growth of the Bauhinia variegata was promoted before 175Gy,and inhibited after 175Gy,another study showed that 50Gy,150Gy could not promoted growth of inflorescence and the number of fruiting of Bauhinia purpurea,inhibited flowering period of individual.?3?Effects of radiation on the biomass and physiological characteristics of Bauhinia variegata and Bauhinia purpurea showed that:Fresh weight and dry weight were respectively highest in 0Gy and 200Gy,fresh weight ratio and dry weight ratio were respectively highest in 200Gy and 175²00Gy,which were among the treatment group of Bauhinia variegata and Bauhinia purpurea.The accumulation of organic matter cound reach the top in 200Gy of Bauhinia purpurea.The content of soluble protein and total activity of SOD of Bauhinia variegata were significantly higher than those in control group,which were the highest in 200Gy.The content of soluble protein and total activity of SO D increased at first and then decreased with the increasing of radiation dose,which were the highest in 225 Gy.Total activity of MDA of Bauhinia variegata and Bauhinia purpurea was respectively the highest in 175Gy and 250Gy.?4?Effects of radiation on the chlorophyll content and photosynthetic characteristics of Bauhinia variegata and Bauhinia purpurea showed that:The content of chlorophyll a of Bauhinia variegata was decreased with the increasing of radiation dose,the content of chlorophyll b was highest in 225Gy,the content of total chlorop hyll was higher in the range of 175²25Gy.The content of chlorophyll a,chlorophyll b and total chlorophyll of Bauhinia purpurea increased at first and then decreased with the increasing of radiation dose,which were higher in the range of 175²25Gy.With the increasing of radiation dose,net photosynthetic ratio,stomatal conductance and transpiration ratio of the two plants increased at first and then decreased,which was highest in 200Gy and 225Gy respectively,and intercellular CO₂ concentration both increased.?5?The results of the optimal radiation dose and selection of phenotypic mutant of M1showed that:The optimal radiation dose of Bauhinia variegata and Bauhinia purpurea were respectively about 200Gy and 225Gy.About 30 dwarfed and multi-branched plants,one yellow and green leaves plant of Bauhinia variegata were selected,one leaf curly plant,one lateral branch creeping plant,one dwarfed and smaller leaves plant,six dwarfed and multi-branched plants of Bauhinia purpurea were selected.?6?There were significant differences in the phenotypic variation among and within populations of threre species in Bauhinia,some phenotypic traits had significant differences among the ten populations.The variation of the phenotypic traits was lower within populations than that among populations,flower number and inflorescence number had the highest variation coefficients.The correlation analysis showed that there were significant correlation among some phenotypic traits.Principal component analysis showed that the largest contribution to phenotypic diversity were summarized as flower,inflorescence and leaf ornamental factors,especially the petal factor.UPGMA cluster analysis showed that the relationship between Bauhinia blakeana and Bauhinia purpurea was closer from the phenotypic diversity point of view.The ten cultivated populations could be divided into three groups in Bauhinia purpurea,four groups in Bauhinia variegata and three groups in Bauhinia blakeana,The clustering results of three species were closely related to leaf size,flower size,inflorescence size and number of flowers.Petal factors could be focused on consideration as breeding goals of Bauhinia in future.