Study On The Change Regularity Of Leaf And Flower Characteristics Of Three Species Of Saussurea In The Eastern Of Qinghai Tibet Plateau With Altitude

The Qinghai Tibet Plateau has complex and diverse topography and extreme climate conditions.The region has not only abundant vegetation types,but also breeds many unique species.The comprehensive environmental factors such as altitude have a great influence on the growth,development and reproduction of plants.For example,with the increase of altitude,the surrounding environment conditions will be more and more severe(such as strong ultraviolet radiation,strong wind,temperature and humidity),and in high altitude areas,because of the small number of insect species and the short growing season of plants,the pollination efficiency of plants is low.How the plants grown at different altitudes adapt to stressful environment is one of the hot issues in the field of ecology in recent years.In order to adapt to the complex and changeable environment,the leaf and flower characteristics are evolving with the changes of the surrounding environment.In this paper,Saussurea parviflora,S.epilobioides and the intermediate species of S.parviflora and S.epilobioides distributed in the eastern of the Qinghai Tibet Plateau were selected as research materials to analyze the variation of leaf and flower characteristics of each population at different altitudes.altitude and to explore the relationship between leaf,flower characteristics and plant size of populations at different altitudes.Through this study,the response mechanism of leaf and flower characteristics of three species of Saussurea at different altitudes was clarified,and their ecological adaptability was discussed,the results are expected to provide theoretical basis for the evolutionary ecology of the species of Saussurea,and also have important practical significance for the restoration of degraded grassland in the plateau.The main results show that:(1)The individual size and plant height of the three species of Saussurea showed a decreasing trend with the increase of altitude.It shows that in alpine areas,the species of Saussurea can respond to the stressful environment in high altitude areas by reducing individual size and plant height.(2)Altitude also has an important influence on the leaf characteristics of the three species of Saussurea.With the increase of altitude the leaf area and specific leaf area decreased significantly,but the leaf dry weight and leaf dry matter content increased significantly.The changes of leaf characteristics of three species of Saussurea may be related to the light intensity and temperature at high altitude,showing adaptive response to the changes of climate and temperature at high altitude.(3)There is a significant trade-off relationship between the floral characteristics(mass and amount of capitulum and tubular floret)of the three species of Saussurea(The biomass increased and the quantity decreased gradually),and the style length,style branch length,filament length and anther length gradually increase with the increase of altitude,The results showed that the three species of Saussurea put limited resources into flower display under high altitude stressful environment,in order to improve the floral components and attract a small number of pollinators in alpine areas.(4)The leaf and flower characteristics of the three species of Saussurea have a certain individual size dependence,and the dependence of the same trait on individual size is different in different species,and the individual size dependence of the same species is different due to different traits.To some extent,the size dependence of each trait reflects the phenotypic plasticity of plants under different environmental conditions.