Salt Stress Effect on Photosynthetic Parameters of Three Quinoa Accessions Grown in Open Field

This study has focused on salt stress effect on photosynthetic parameters of three quinoa accessions (18GR, R-132 and DE-1), grown in open field that were measured at the end of panicle, flowering and fruiting stages. At panicle stage, when these accessions were irrigated by 100 and 150 mM of NaCl, they showed an increase of chlorophyll relative content compared to the control (41.8 and 42.5 mmol for 18GR; 39.2 and 43.8 mmol for R-132 and 38.4 and 37.4 mmol for DE-1, respectively). An increase of stomatic conductance was noted also under these concentrations (3193.9 and 2313.5 µmol/m2/s for 18GR, 2225.5 and 3189.3 µmol/m2/s for R-132 and 2025.4 and 1556.1 µmol/m2/s for DE-1, respectively). Photosynthetic activity of 18GR and DE-1was stimulated at 100 mM NaCl by 14 and 44%, respectively, and at 150 mM NaCl by 18% and 22%, respectively. However, this activity showed a decrease for R-132 by 11% compared to the control at 100 mM NaCl treatment. But under 200 mM of NaCl, a decrease of these traits was noted compared to the control and DE-1 accession seems to be less affected. In fact, chlorophyll relative content decreased by 6, 3 and 3%, respectively for 18GR, R-132 and DE-1. Stomatic conductance and photosynthetic activity showed a decrease also by 53.5% and 50.9% for 18GR, 51.6% and 42.9 for R-132 and by 5% and 18.8 for DE-1, respectively. At flowering and fruiting stages, a similar variation of photosynthetic parameters evolution was shown. These latter were positively and significantly correlated (p < 0.01) with total grain yield (from r = 0.5 to r = 0.7) and aerial dry matter (from r = 0.7 to r = 0.9).