Abstract:

The annual herb Agriophyllum squarrosum is an important economic herb for vegetation restoration and construction in the arid area of Northwest China. At present,the impact of drought stress on the functional properties of its leaves has not been fully clarified,which limits the application scenario and ecological use of it to a certain extent. Taking A.squarrosum as the research object,this paper set up four pot water control experiments with water gradients (CK,LD,MD and ED treatments were 90% ± 5%,70%±5%,50%±5% and 30%±5% of the field water capacity respectively),to explore the response characteristics of structural characters of upper and lower leaves and photosynthetic pigment content of A.squarrosum to different degrees of drought stress. The results showed that:1) the response of leaf traits of A.squarrosum at different leaf positions to drought was basically the same. With the increase of drought stress,the specific leaf area (SLA),leaf relative water content (LRWC),total chlorophyll content (Chl) and chlorophyll a content of A.squarrosum leaves decreased significantly,but the time difference of light drought treatment (LD treatment) was not significant. 2) Although the leaf tissue density (LTD) and dry matter content (LDMC) increased gradually with the degree of drought stress,the difference among the treatments did not reach a significant level. 3) The content of chlorophyll b (Chl b) decreased only slightly under drought,and the content of carotenoid (Car) changed little among drought treatments. 4)Under the four water treatments,there were significant differences in leaf position between SLA and LRWC of A.squarrosum leaves,the SLA of upper leaves was 12.34% higher than that of lower leaves,and its LRWC was 4.37% lower than that of lower leaves. There was a significant interaction between drought stress and leaf position on LRWC in A.squarrosum leaves. Therefore,when selecting A.squarrosum for large-scale vegetation restoration,the relative water content of leaves can be used as an important physiological index to measure the individual adaptation of A.squarrosum to soil water changes. The results can provide a theoretical reference for vegetation restoration and sustainable ecological management of forest and grass in sandy areas.

Key words: Agriophyllum squarrosum, leaf functional traits, drought stress, Chlorophyll content, specific leaf area, leaf relative water content