A study on physiological parameters of barley with an emphasized comparison between two-rowed and six-rowed types.

摘要

Several physiological parameters including carbon isotope discrimination, gas-exchange, and chlorophyll fluorescence parameters were studied on several barley cultivars/breeding lines under field and greenhouse conditions. Gas-exchange parameters include carbon assimilation rate, transpiration rate, stomatal conductance, and instantaneous water-use efficiency. Barley has two ear structures, two-rowed and six-rowed, which are simply controlled at their genetic level. Under field conditions, these two ear types were compared with all the physiological traits listed above under irrigated and non-irrigated environments. It was found that these two ear types had different carbon isotope discrimination values for grain, awn, and flag leaf. Carbon atoms in two-rowed types were usually isotopically heavier than that in six-rowed barleys, indicating higher water-use efficiency. There was a strong correlation between grain yield and carbon isotope discrimination of flag leaf, awn, and grain when these two ear types were combined for analysis. Carbon isotope discrimination of mature awns and grains was a good predictor of grain yield for both ear types under low to moderate water stress. There were significant differences in ear but not in flag leaf or awn gas-exchange parameters with the exclusion of instantaneous water-use efficiency. Awns significantly contributed to ear gas-exchange under growth-chamber conditions. The minimum, maximum, and steady chlorophyll fluorescence parameters for light-adapted leaves showed differences between these two ear types when cultivars/breeding lines were used in field conditions with high irradiance. In greenhouse environments, 14 barley genetic lines were studied for their saltinity tolerance using these physiological parameters. A two-week saline treatment decreased gas-exchange parameters, carbon assimilation rate and stomatal conductance, chlorophyll fluorescence parameters (i.e., effective quantum yield of photosystem II, photochemical quenching), and carbon isotope discrimination. Relations between stomatal conductance and aboveground dry matter, carbon assimilation rate, actual quantum yield of photosystem II electron transport, and the ratio of electron transport rate over net assimilation rate were strongly significant. Stomatal conductance could provide the best information to assess how different barley lines respond to salinity stress. Other parameters were of limited value as criteria to assess salinity tolerance.