Abstract:

In order to elucidate the adaptation and ability of different xerophilous plants to soil water availability and provide the theories of vegetation regeneration for western desert areas in China, the photosynthetic physio_ecological characteristics and the contents of leaf chlorophyll, soluble sugar, starch, nitrogen, phosphorus and kalium of two desert plants (Atraphaxis frutescens and Elaeagnus angustifolia in response to ground water availability were investigated in a controlled environment at the Plant Transpiration Consume Water Observation Station in Minqin Desert Botanical Garden, Gansu province. In this experiment, the depths of groundwater (DGW) were set at three levels: 1.4 m, 2.4 m and 3.4 m. In each treatment, the two desert plants were transplanted to the observation sites with different DGW after growing naturally for 3 or 4 years. The contents of leaf chlorophyll, soluble sugar, starch, nitrogen, phosphorus and kalium of the two desert plants were measured by the methods described in “Experimental manual of plant physiology” and the photosynthetic measurements were conducted by using an open gas_exchange system (LI_6400P, LI_COR Inc. Lincoln, NE,USA).The results showed that: 1) the three different DGW treatments resulted in a marked soil moisture gradient; 2) The changes of DGW led to significant changes in the leaf content of chlorophyll a (Chl a), chlorophyll b (Chl b), total chlorophyll (Chl a+Chl b) and the ratio of Chl a to Chl b (Chl a/Chl b) (p<0.01); 3) The increment of DGW depths caused the increase of soluble sugar content and the decrease of starch content irrespective of plant species, but the extent of these changes varied between the two species; 4) Increased DGW caused a decrease in the content of nitrogen, phosphorus and kalium; 5) The changes of either increase or decrease in chlorophyll a, chlorophyll b, total chlorophyll, nitrogen, phosphorus, kalium, soluble sugar, starch and the ratio of Chl a and Chl b of A. frutescens and E. angustifolia varied with DGW. The original conclusions were drawn as follows: compared with A. frutescens, E. angustifolia may be more adaptive to the dry desert environment. Since E. angustifolia is a nitrogen_fixing species, further studies are needed to verify whether the differences between these two species are related to nitrogen fixation. 