[Effects of drought, CO2 concentration and temperature increasing on photosynthesis rate, evapotranspiration, and water use efficiency of spring wheat].

The effects of drought, CO2 concentration and temperature increasing on development period, photosynthesis rate (Pn), evapotranspiration (ET), and water use efficiency of spring wheat were investigated. The results showed that elevated CO2 concentration (550, 700 mumol.mol-1) could lengthen heading-ripening period, but high temperature (average diurnal temperature increase 4.8 degrees C), which made heading-ripening period shorten and speeded the seedling under treatment of both high CO2 concentration and high temperature, affected growing period more than high CO2 concentration. The combined effects of elevated CO2 concentration and temperature enhanced Pn, stomatal resistance (r), leaf water use efficiency (WUEl), and whole-canopy water use efficiency (WUE), while transpiration rate (E) were not significantly affected. The effects on ET depended on soil moisture. High CO2 concentration and high temperature enhanced ET under high (75%-85% field water capacity) and middle (55%-65% field water capacity) soil moisture, but decrease ET under low soil moisture (35%-45% field water capacity).