Indicative effect of the anatomical structure of plant photosynthetic organ on WUE in desert region

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 ( delta super(13) C 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 delta super(13) C values in plants to environment factors. Therefore, there must exist an important relevance between plant anatomical structure and delta super(13) C 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 delta super(13) C value. In this paper, the relationship between plant anatomical structure and delta super(13) C 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 < delta super(12) C 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 delta super(13) C values indicated that: there was a significantly positive correlation between delta super(13) C value and Tl or Da, with the correlation coefficient 0.719 (P