Three winter wheat (Triticum aestivum L.) cultivars, representatives of those widely cultivated in Beijing over the past six decades, were grown in the same environmental conditions. Net photosynthetic rate (PN) per unit leaf area and instantaneous water use efficiency (WUE) of flag leaves increased with elevated CO2 concentration. With an increase in CO2 concentration from 360 to 720 µmol mol-1, PN and WUE of Jingdong 8 (released in 1990s and having the highest yield) increased by 173 and 81 %, while those of Nongda 139 (released in 1970s) increased by 88 and 66 %, and Yanda 1817 (released in 1945, with lowest yield) by 76 and 65 %. Jingdong 8 had the highest PN and WUE values under high CO2 concentration, but Yanda 1817 showed the lowest PN. Stomatal conductance (gs) of Nongda 139 and Yanda 1817 declined with increasing CO2 concentration, but gs of Jingdong 8 firstly went down and then up as the CO2 concentration further increased. Intercellular CO2 concentration (Ci) of Jingdong 8 and Nongda 139 increased when CO2 concentration elevated, while that of Yanda 139 increased at the first stage and then declined. Jingdong 8 had the lowest Ci of the three wheat cultivars, and Yanda 1817 had the highest Ci value under lower CO2 concentrations. However, Jingdong 8 had the highest PN and lowest Ci at the highest CO2 concentration which indicates that its photosynthetic potential may be high. and H. Q. Liu ... [et al.].
We studied the responses of gas exchange, leaf morphology, and growth to irradiance in Taihangia rupestris, a naturally rare herb inhabiting only vertical cliff faces. In low irradiance (LI, 10 % of full sun) T. rupestris had lower net photosynthetic rate (PN) and produced much less leaves, total leaf area, and biomass than in high (HI, full sun) or medium irradiance (MI, 50 % of full sun). PN of T. rupestris was higher in HI than in MI on August 8, but lower in HI than in MI on September 22. T. rupestris had shorter petioles and lower leaf area ratio, and produced more but smaller and thicker leaves in HI than in MI. In HI the fast production of new leaves may guarantee T. rupestris to maintain higher PN at the whole plant level and thus accumulate more biomass at harvest, although the single-leaf PN may become lower as found on September 22. Hence T. rupestris possesses a latent capacity to acclimate and adapt to full sun. Irradiance, therefore, may not be a responsible factor for the restricted distribution of T. rupestris on vertical cliffs. and Min Tang ... [et al.].