The Effect Of Seed Size And Altitude On The N?P Content Of Seeds Of Common Plants On The Northeastern Qinghai-Tibet Plateau

The component and allocation of C?N?P content in plants has been a hot issue in ecological research as integral parts in the process of plant growth.These studies involved in different levels(individual?population?community),different functional groups and their correlation with environmental conditions.But the relationship between C?N?P percentage content of seeds and environmental conditions was rarely involved.Although seed size is a relatively stable trait,it is still great in interspecific and intraspecific variation with changeable environment.So the seed nutrients would be changed to adapt to changeable environmental with seed size variation.In this study,we discussed the effect of seed size and altitude on the C,N,P percentage content of seeds of 274 common plants species on the northeastern Qinghai-Tibet Plateau,and provided theoretical evidence for discussing the response of plants to environmental change.Seed size was defined by the average of three samples with hundred seeds,and element percentage content of seeds was measured with Dichromate External Heating and Flow Injection Analyzer.The results showed:(1)The seed size of most of 274 species were smaller and ranged from 0.0203 to 611.86 mg,the seed size of more than 50%of the species had the value between 0-1mg.Seed size was significantly negatively correlated with altitude gradients.(2)The C?N?P percentage content and its ratio were all significantly different in 274 species,the variation of C?N?P percentage content and its ratio were 39.43-76.68%(C)?0.655-9.485%(N)?0.067-1.465%(P)?4.729-77.44(C/N)?27.28-760.8(C/P)?2.968-29.45(N/P)respectively.(3)C?N?P percentage content were all significantly negatively correlated,and C/N?C/P?N/P values were significantly positively correlated with increasing seed size.The correlations between C?N?P percentage content and altitude were significantly positive,C/N?C/P values were significantly negatively correlated with increasing altitude,N/P value is negatively correlated with altitude,but not significantly.(4)Within Umbelliferae species,the C?N?P percentage content or its ratio didn't show significantly variation with increasing seed size or altitude gradients;within Legume species,the correlation between C?N?P percentage content or its ratio and seed size were also not significantly,N?P percentage content were not significantly positively correlated with altitude gradients,C percentage content and C/N?C/P?N/P values decreased with increasing altitude;within Asteraceae species,P percentage content were significantly negatively correlated with seed size,C/P?N/P values were significantly positively correlated with seed size.The correlation between C?N percentage content or C/N value and seed size were not significantly,and the similar correlation between C?N?P percentage content or its ratio and altitude;within Ranunculaceae species,the correlation between C?N?P percentage content or its ratio and seed size were not significantly,C percentage content?C/N?C/P?N/P values were negatively correlated with increasing altitude,N?P percentage content were positively correlated with increasing altitude.Studies suggested that:the decreased C percentage content and increased C/N?C/P values among larger seeds suggested that more accumulation in carbohydrates than lipids could provide more energy supply for the initial growth of seedlings come from larger,and then the seedlings could gain competitive advantage than those from smaller seeds.The lower C/N?C/P value of smaller seeds or species from high altitude suggested increased proportion of living material,such as proteins and phospholipids.More N and P percentage content in seeds could provided enough genetic materials and improve the ability of protein synthesis for earlier seedling growth,which could help the seedlings to gain rapid growth rate,enhance their adaptability to harsh environmental conditions at high altitude and their survival rate,and similarly,could overcome the disadvantages of smaller seedling from smaller seeds.Thus,the variation of C?N?P percentage content with increasing seed size and altitude might be the result of adaptation.