Studies On Stomas And Photosynthetic Characteristics Of Heteromorphic Leaves Of Populus Euphratica

The leave shapes of adult Populus euphratica varied from lanceolate to dentate broad-ovate. In order to discover the ecological adaptation mechanism of the varied typical leaves, the lanceolate(A), broad-ovate(B) and dentate broad-ovate(C) leaves were chosen to investigate their Properties of Photosynthetic Ecology and Physiology.The stomas on the upper and lower epidermis were measured using FEI QUANTA 200 san telescope. The results showed that The stomatal densities decreased from A to C. and the stomas open unequally, furthermore their sunken depth and chamber size varied obviously, which gradually reduced from A to C.The photosynthetic rate of the three typical leaves were investigated using Ciras-2 porable photosynthesis system. The results showed that the diurnal photosynthetic rate in sunny day varied with single peak curves. The results showed that under normal atmospheric CO₂ concentration and 1000 μnolm ^-2s^-1 of light intensity, the photosynthetic rates of A ,B and C were 11.6, 14.8 and 7. 9μnolm^-2s^-1respectively, and water use effcicency(WUE) were 1.63, 1. 53 å’Œ 1. 28 μ mol CO₂ mmor^-1H₂O. Under these conditions, the light saturation and compensation point of A were 1100 and 53μnolm^-2s^-1 respectively, while the corresponding values of B were 1100 and 42 μnolm^-2s^-1, the values of C were 800 and 86 μnolm^-2s^-1. When CO₂ concentration was 460 μnolmol^-1 and light intensity was 1000 μnolm^-2s(-1), water use effcicency(WUE) of A, B and C increased, in detail WUE of A increased by 0. 81 μmolCO₂CO₂ mmol^-1 H₂O WUE of B increased by 1.26μ mol CO₂ mmol^-1 H₂O and WUE of C just increased by 0. 25 μ molCO₂ mmol^-1 H₂O. The light saturation points of A, B and C showed significant change. The light compensation points of A and B increased a little, while the light compensation point of C increased obviously.The chlorophyll fluorescence parameters of the three typical leaves wereinvestigated using PAM2100. The results showed that the minimal fluorescence (Fo) of the A was the lowest and the maximal fluorescence (Fm) of the A was the highest. The relative electron transport rate(ETR) was B>A>C, the efficiency of solar energy conversion(Fv/Fm) and potential activity(Fv/Fo) of the PS II in the leaves were different, which of the A was the highest.The results implied that their leaf shapes, anatomic structures and photosynthetic characteristics varied during the leaf development to adapt them to the desert climate where they existed.