Gas exchange and Triticum sp. with different ploidy in relation to irradiance

Different species of Triticum were grown during a greenhouse experiment, including T. monococcum L., T. dicoccum Schrank, T. durum Desf., T. spelta L. and T. aestivum cv. Vánek. The goal was to establish the influence of irradiance on the parameters of photosynthetic performance in relation to their ploidy. Photosynthetic rate (Pn), transpiration (E) and stomatal conductance (gs) were measured at irradiance ranging from 217–1305 μmol/m2/s. In all monitored species, saturation irradiance for photosynthesis at the level of 609 μmol/m2/s was reached. The highest average Pn was measured in the diploid T. monococcum (32.5 μmol CO2/ m2/s) while the lowest Pn occurred in the hexaploid T. spelta (22.0 μmol CO2/m 2/s). The Pn in hexaploid T. aestivum (29.6 μmol CO2/m 2/s) was comparable with the tetraploid T. durum. Similarly, E also decreased with the increase of ploidy. The highest gs was measured in T. durum (1.03 mol CO2/m 2/s) and T. aestivum (0.99 mol CO2/ m2/s). In all monitored species a close linear dependency was recorded between Pn and gs. Species with lower ploidy reach maximum values of Pn with lower gs. Hexaploid T. aestivum and tetraploid T. durum, require higher gs in order to achieve higher Pn and yet they do not reach the Pn values of species with lower ploidy.