Abstract: As an important supplementary water source, dew plays an irreplaceable role in the desert ecosystem. Changes in input amount of dew can exert an important impact on the ecological processes of ephemerals. The effect of dew input on water and photosynthetic physiology of Lappula semiglabra seedlings were investigated under three simulated dew levels, reduced amount (W₀), natural amount (W₁) and doubled amount (W₂), in Ebinur Lake Wetland National Nature Reserve in Xinjiang, China. The results showed that doubled dew treatment significantly improved plant water status of seedlings, whereas reduced dew treatment decreased leaf water potential and water content of seedlings to some degrees. Under reduced dew treatment, the transpiration rate and net photosynthetic rate of seedlings (P<0.05) decreased significantly, moreover, the net photosynthetic rate changed from doublepeak curve to singlepeak curve. Doubled dew treatment delayed the reduction process of stomata conductance of seedlings, while reduced dew treatment decreased stomata conductance of seedlings. Difference in dew input amount had no significant effect on intercellular CO₂ concentration. The instantaneous water use efficiency of the leaves of L. semiglabra seedlings did not exhibit marked difference (P>0.05) under different dew input amounts (P>0.05), which indicated a stable water use strategy of desert ephemerals.

Key words: Euphausia superba, population structure, sexual maturity stage, Scotia Sea, sex ratio