Abstract:

The shapes of the leaves of adult Populus euphratica are varied from lanceolate to dentate broad-ovate. In order to find the ecological adaptation mechanism of the varied typical leaves, the dentate broad-ovate、broad_ovate and lanceolate leaves as the typical leaves were chosen to study their stomatal and photosynthetic characteristics. It is observed that the stomas on the adaxial and abaxial epidermis of the same leaves open unequally and their densities are similar. The stomatal densities of the three typical leaves are different, which decrease from broad-ovate to lanceolate leaves. Their stomatal sunken degree varies obviously, which is lessened from broad-ovate to lanceolate leaves. The changes of the diurnal photosynthetic rate of the three typical leaves are basically accordant with a curve of single apex. The average values of the diurnal photosynthetic rate of these leaves are different, which decrease from broad-ovate, dentate broad-ovate leaves to lanceolate. The compensation points of light are similar in the three typical leaves, while the saturation points of light are varied obviously among them. The efficiency of solar energy conversion and potential activity of the PSⅡ in the leaves are distinct, which of the dentate broad-ovate leaves is the highest. The results imply that their leaf shapes, anatomic structures and photosynthetic characteristics are varied during the leaf development.

Key words: Populus euphratica, polymorphic leaves, stoma, photosynthetic characteristics, chlorophyll fluorescence