Abstract:

Leaf shapes are not only useful indicators in plant taxonomy, but also important factors affecting energy and material exchange in leaves. In this paper, we collected and scanned the leaves of Nitraria tangutorum in Dengkou and Minqin and N.sphaerocarpa in Dunhuang, and then analyzed leaf shape parameters with Image-Pro Plus6.0 image processing software and leaf δ¹³C values in the isotope laboratory of the Chinese Academy of Forestry. The result showed that: 1) as leaf area increased with increasing water availability the increases in the leaf length and width were asynchronously. 2) with the same leaf width, the leaves of N. tangutorum and N. sphaerocarpa were significantly longer in high water available conditions. 3) although there were significantly differences in water availability between Dengkou and Minqin, as well as between the bottom and middle of the alluvial fan near the East Lake in Dunhuang, the leaf δ¹³C values of N. tangutorum or N. sphaerocarpa were similar in different water conditions (P>0.05). Our results suggested that the ratio of leaf perimeter to area would be an important factor which linked leaf shape to plant water physiology. During growing procedure of leaf area, leaf length increase was prior to its width to alleviate the reduction in ratio of perimeter to area and maintain water use efficiency of the plant.

Key words: Nitraria tangutorum, Nitraria sphaerocarpa, leaf shape, water availability, leaf &delta, ¹³C