Carbon balance of cultivated and wild barley under salt stress and calcium deficiency

Combined effects of mixed sulphate salinity (Na2SO4 + MgSO4) and contrasting calcium supply on whole-plant daily carbon balance, and on growth and maintenance respiration were investigated in cultivated barley (Hordeum vulgare L. cv. Harrington) and wild barley (H. jubatum L.) grown hydroponically in a controlled environment chamber. Daily carbon balance was more positive in wild barley than in barley in the salinity plus low calcium treatment (LCa). The additional calcium in the salinity plus high calcium treatment (HCa) lessened part of the adverse effects of salinity on carbon balance in H. vulgare. The LCa treatment reduced whole-plant growth conversion efficiency (Y-g) more in H. vulgare than in H. jubatum. HCa treatment significantly improved Y-g in H. vulgare, but not in H. jubatum, relative to the LCa treatment. The maintenance coefficient (m) remained unchanged from the control in treated H. jubatum, while it showed a slight increase under HCa but a significant reduction under LCa in H. vulgare. The greater salt tolerance in H. jubatum under LCa can be attributed, at least in part, to its ability to maintain a greater Y-g than H. vulgare. Supplemental calcium ameliorated the deleterious effects of salinity on H. vulgare growth, thereby improving its salt tolerance. Differences in tissue composition could not explain the effects of salinity and calcium supply on growth and maintenance respiration components in either species.