Carbon Assimilation, Isotope Discrimination, Proline and Lipid Peroxidation Contribution to Barley (Hordeum vulgare) Salinity Tolerance

Ioannis Vasilakoglou; Kico Dhima; Anastasia Giannakoula; Christos Dordas; Vasiliki Skiada; Kalliope Papadopoulou

doi:10.3390/plants10020299

Carbon Assimilation, Isotope Discrimination, Proline and Lipid Peroxidation Contribution to Barley (Hordeum vulgare) Salinity Tolerance

Plants (Basel). 2021 Feb 4;10(2):299. doi: 10.3390/plants10020299.

Authors

Ioannis Vasilakoglou¹, Kico Dhima², Anastasia Giannakoula², Christos Dordas³, Vasiliki Skiada⁴, Kalliope Papadopoulou⁴

Affiliations

¹ Department of Agriculture-Agrotechnology, University of Thessaly, 415 00 Larissa, Greece.
² Department of Agriculture, International Hellenic University, 574 00 Echedoros, Greece.
³ Faculty of Agriculture, Forestry and Natural Environment, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece.
⁴ Department of Biochemistry and Biotechnology, University of Thessaly, 415 00 Larissa, Greece.

Abstract

Barley (Hordeum vulgare L.) exhibits great adaptability to salt tolerance in marginal environments because of its great genetic diversity. Differences in main biochemical, physiological, and molecular processes, which could explain the different tolerance to soil salinity of 16 barley varieties, were examined during a two-year field experiment. The study was conducted in a saline soil with an electrical conductivity ranging from 7.3 to 11.5 dS/m. During the experiment, a number of different physiological and biochemical characteristics were evaluated when barley was at the two- to three-nodes growing stage (BBCH code 32-33). The results indicated that there were significant (p < 0.001) effects due to varieties for tolerance to salinity. Carbon isotopes discrimination was higher by 11.8% to 16.0% in salt tolerant varieties than that in the sensitive ones. Additionally, in the tolerant varieties, assimilation rates of CO₂ and proline concentration were 200% and up to 67% higher than the sensitive varieties, respectively. However, in sensitive varieties, hydrogen peroxide and lipid peroxidation were enhanced, indicating an increased lipid peroxidation. The expression of the genes Hsdr4, HvA1, and HvTX1 did not differ among barley varieties tested. This study suggests that the increased carbon isotopes discrimination, increased proline concentration (play an osmolyte source role), and decreased lipid peroxidation are traits that are associated with barley tolerance to soil salinity. Moreover, our findings that proline improves salt tolerance by up-regulating stress-protective enzymes and reducing oxidation of lipid membranes will encourage our hypothesis that there are specific mechanisms that can be co-related with the salt sensitivity or the tolerance of barley. Therefore, further research is needed to ensure the tolerance mechanisms that exclude NaCl in salt tolerant barley varieties and diminish accumulation of lipid peroxides through adaptive plant responses.

Keywords: carbon isotope discrimination; gene expression; hydrogen peroxide; lipid peroxidation.