Study On The Ecological Adaptability Of Four Kinds Of Climatis In Tibet

In this study,four Clematis(C.tenuifolia,C.tangutica,C.connata and C.Montana)in Tibet were selected as the research objects,and the ecological adaptability of the four Clematis in Tibet was studied through experiments on seed morphological characteristics,determination of water content and biomass in each organ of the plant,plant photosynthetic characteristics,plant physiological response under drought stress and changes of endogenous hormones.The research results are as follows:(?)the size and morphological characteristics of seeds have influence on the diffusion of plant seeds,and are the ways and manifestations of plants'adaptability to the environment.The seeds of the four Clematis species in Tibet differ significantly in size and morphology,all of which promote seed diffusion by reducing seed quality and diffusion resistance,increasing pilose,and enhancing diffusion assistance.At the same time,Clematis seeds enhance the viability of seeds by enhancing their water absorption characteristics,thus promoting the proliferation and development of the population.The seed indexes of C.tenuifolia showed good performance and strong adaptability,followed by C.tangutica.(?)the root width of four clematis species in Tibet is inversely proportional to the number of lateral roots and the maximum root length.The longitudinal root development of C.tenuifolia and C.tangutica is better than that of C.connata and C.Montana,while the root system deep into the land and developed lateral roots can effectively absorb moisture and nutrients in the soil,promote the growth of plants,and at the same time enhance the ability to resist changes in the adverse external environmen.(?)by comparing the differences in water content and water ratio of the four Clematis species in Tibet,it can be found that the four Clematis species all have the highest water content in their roots,and the water content is first distributed to the roots in the water ratio.The water content and water ratio of leaves and reproductive branches were lower.The water content of the reproductive shoot is higher than that of the leaf.These are one of the ecological adaptations of the four Clematis species.In this aspect,the most adaptive clematis species is C.tangutica,followed by C.tenuifolia,and the least adaptive clematis species is C.connata.(?)biomass accumulation and distribution of 4 species of clematis in Tibet showed that the biomass of 4 species of clematis was first distributed in stems.Moreover,the biomass in the root is also very high,which indicates that the four Clematis species adopt the strategy of energy distribution equilibrium,that is,the distribution of biomass to the underground can provide effective support for the aboveground parts to resist drought,lack of nutrients and expand canopy,so as to enhance their stress resistance.The higher reproductive ratio than leaf biomass ratio and the smaller root to crown ratio can accelerate Clematis population to escape from the unfavorable growth environment and to the suitable breeding environment,thus promoting the development of Clematis population.This important mode of resource allocation is to make an adaptive choice to adapt to the environment and climate of Tibet.In terms of biomass allocation,the adaptability of C.tenuifolia and C.tangutica is obviously better than that of C.connata and hydrangea,while the adaptability of C.montana is the weakest among the four clematis species.(?)the daily average net photosynthetic rate(Pn)of C.tangutica and C.tenuifolia were significantly higher than that of C.montana and C.connata(P<0.05),among which the daily average net photosynthetic rate(Pn)of C.tangutica was the highest.Clematis through comprehensive comparison,C.tenuifolia,C.tangutica,C.connata,C.connata silk cane handle four plants of the genus C.of transpiration rate(Tr),stomatal conductance(Gs),water use efficiency(WUE),intercellular CO2concentration(Ci)that there was a significant difference between the indicators of C.tenuifolia thread is superior to the other three species of Clematis plants,followed by the,C.tangutica and handle the worst Clematis.(?)in the early stage of drought,the enzyme protection system of the four Clematis species in Tibet was the first to respond quickly and remove the reactive oxygen species,making Clematis plants tolerant to drought.As the drought continues to increase,four kinds of Clematis plants produce SOD accumulation is overmuch,and POD activity,CAT activity did not response rapidly,eliminate the inter-action between reduced,SOD reaction of H₂O₂cause damage to the plant itself,and also caused by the drought stress free oxygen,Clematis plants PRO began to rise dramatically,absorb water through its osmotic regulation function,relieve the damage of drought stress,and improve adaptability to drought.In the later stage of drought,there is a large amount of water loss and excessive reactive oxygen species,which leads to a decline in SOD,POD,CAT and PRO of the four Clematis species,a weakening of the cell protection system,a rapid increase in MDA content,great damage to plants and a weakening of drought resistance.The correlation of drought resistance indexes of the four Clematis species showed that SOD,POD,CAT and PRO were all beneficial indexes,and all were significantly correlated.The results of the evaluation system of the subordinate function showed that C.tangutica had the best performance and C.tenuifolia had the second best performance.(?)4 kinds of Clematis under drought stress,the content of endogenous hormones are changing,including abscisic acid(ABA)and zeatin(ZT)content increase gradually with drought stress increase,but the trend is different,the former in the face of drought stress,rapid response,content increased rapidly,and zeatin(ZT)in the early stage of the drought stress growth compared with the former slow,reflecting the zeatin(ZT)by drought stress in four kinds of clematis response sensitivity as abscisic acid(ABA).With the increase of drought stress,the content of auxin(IAA)and gibberellin(GA3)decreased.