Search

Affected by the extreme arid environment caused by salinization,high temperature and intensive radiation,desert plants change their structural characteristics,such as fleshy leaf,assimilating shoots,lots of epidermal hairs,thick cuticle and so on,to improve their water use efficiency.Structure being basis of function,the anatomic structure of photosynthetic organ(including leaf and assimilating shoot) of desert plants can indicate their water use efficiency.It has been improved that stable carbon isotope(δ13C value),an indicator of long-term water use efficiency(WUE) of desert plants and a comprehensive value reflecting the whole life history of plants,was widely applied to illustrate the response of δ13C values in plants to environment factors.Therefore,there must exist an important relevance between plant anatomical structure and δ13C value to some degree.However,most of studies on plant anatomical structure have been focused on its relationships with drought resistance,environmental plasticity and plant taxonomy for a long time,little was known about its response to WUE indicated by δ13C value.In this paper,the relationship between plant anatomical structure and δ13C value was analysed in the middle reaches of Heihe River basin,in order to find an effective indicator for WUE from the point of plant anatomical structure.The results showed that:(1)all the plants with axial photosynthetic organs had higher δ13C values that those with leafy organs but Hedysarum scoparium.(2) The variation range of thicknesses of the photosynthetic organs and different tissues among different desert plants was large.The maximum value of the leaf thickness(Tl) or axis diameter(Da) was 6.9 times higher than the minimum,and those of cuticle thickness(Tc),epidermis thickness(Te),palisade tissue thickness(Tp),spongy tissue thickness(Ts) and aqueous tissue thickness(Ta) were 5.8,11,4,3.5 and 3.5 times higher than the corresponding minimum,respectively.Tl or Da and Te of most desert plants with axial photosynthetic organs were higher than those with leafy organs.(3)The correlation analysis between different tissue thicknesses of desert plants and their δ13C values indicated that: there was a significantly positive correlation between δ13C value and Tl or Da,with the correlation coefficient 0.719(P0.01),while the correlations of δ13C value with other tissue thicknesses were not significant.In conclusion,from the point of the anatomic structure of photosynthetic organs of desert plants,WUE could be indicated by Tl or Da.The higher Tl or Da,the higher WUE desert plant possesses,and WUE of plants with axial photosynthetic organs are higher than those with leafy organs.