Photosynthetic characteristics of ear and flag leaves of wheat species, tetraploid Triticum dicoccoides Kom and hexaploid Bima1, were studied in plants grown under well-watered (WW) and water-stressed (WS) conditions. Compared to ears, flag leaves exhibited higher photosynthetic rate (PN) at the filling stage, but more severe decrease under WS. PN in the tetraploid wheat ear remained higher than that in the hexaploid wheat during the grain-filling stage. Water stress decreased PN in both the organs; this decline was caused by a reduction in Rubisco activity, not by drought-induced stomatal limitation. Tetraploid wheat ears exhibited higher relative water content and water-use efficiency than that of hexaploid wheat, under WS. The change in phosphoenolpyruvate carboxylase activity and carbon isotope composition indicated the absence of C4 metabolism in the ears of both species under both conditions. The improved performance of the tetraploid wheat ears under WS was associated with better water relations., Y. P. Li, Y. Y. Li, D. Y. Li, S. W. Wang, S. Q. Zhang., and Obsahuje bibliografii