Changhai Shi

Comparison of the effects of symmetric and asymmetric temperature elevation and CO2 enrichment on yield and evapotranspiration of winter wheat (Triticum aestivum L.).

Under the changing climate, asymmetric warming pattern would be more likely during day and night time, instead of symmetric one. Concurrently, the growth responses and water use of plants may be different compared with those estimated based on symmetric warming. In this work, it was compared with the effects of symmetric (ETs) and asymmetric (ETa) elevation of temperature alone, and in interaction with elevated carbon dioxide concentration (EC), on the grain yield (GY) and evapotranspiration in winter wheat (Triticum aestivum L.) based on pot experiment in the North China Plain (NCP). The experiment was carried out in six enclosed-top chambers with following climate treatments: (1) ambient temperature and ambient CO2 (CON), (2) ambient temperature and elevated CO2 (EC), (3) elevated temperature and ambient CO2 (ETs; ETa), and (4) elevated temperature and elevated CO2 (ECETs, ECETa). In symmetric warming, temperature was increased by 3°C and in asymmetric one by 3.5°C during night and 2.5°C during daytime, respectively. As a result, GY was in ETa and ETs 15.6 (P < 0.05) and 10.3% (P < 0.05) lower than that in CON. In ECETs and ECETa treatments, GY was 14.9 (P < 0.05) and 9.1% (P < 0.05) higher than that in CON. Opposite to GY, evapotranspiration was 7.8 (P < 0.05) and 17.9% (P < 0.05) higher in ETa and ETs treatments and 7.2 (P < 0.05) and 2.1% (P > 0.05) lower in ECETs and ECETa treatments compared with CON. Thus, GY of wheat could be expected to increase under the changing climate with concurrent elevation of CO2 and temperature as a result of increased WUE under the elevated CO2. However, the gain would be lower under ETa than that estimated based on ETs due to higher evapotranspiration.

Effect of water stress on leaf level gas exchange capacity and water-use efficiency of wheat cultivars

Water stress constitutes one of the most important environmental constraints limiting wheat productivity worldwide. In an open pot experiments six spring wheat cultivars, viz., Barigom-23, Barigom-24, Barigom-25, Barigom-26, Barigom-27, and Barigom-28 were grown under control and water stress conditions to evaluate their genetic variations for gas exchange parameters and water-use efficiency. Results showed that genotypic variations for the gas exchange parameters and water-use efficiency were very prominent among wheat cultivars under control and water stress conditions. Water stress adversely affected net photosynthesis, stomatal conductance, internal CO2 concentration, transpiration rate, carboxylation efficiency, instantaneous and intrinsic water-use efficiencies compared to control condition. Wheat cultivars Barigom-23 showed best performances for most of the characters. Cultivars Barigom-26 and Barigom-27 showed medium performances, whereas Barigom-24 showed lowest performance for most of the characters under water stress condition. A clear significant positive linear relationship was observed between net photosynthesis and stomatal conductance which indicated that increase in stomatal conductance improves net photosynthesis.