Response of salt-stressed strawberry plants to supplementary calcium nitrate and/or potassium nitrate
A pot experiment was carried out with two strawberry (Fragaria x ananassa Duch) cultivars, Oso Grande and Camarosa in sand culture to investigate the effects of supplementary calcium and potassium nitrate to plants grown at high NaCl (35mM) in complete nutrient solution supplied via roots. Treatments were (1) nutrient solution alone (C), (2) C+5mM Ca(NO)+5mM KNO (C+CaN+KN), (3) nutrient solution+35mM NaCl (C+S), (4) C+S+5mM Ca(NO) (C+S+CaN), (5) C+S+5mM KNO (C+S+KN), and (6) C+S+5mM Ca(NO)+5mM KNO (C+S+CAN+KN). The plants grown at high NaCl had less dry matter, fruit yield, and chlorophyll content than those grown in normal nutrient solution for both cultivars. Both supplementary Ca(NO) and KNO treatments significantly ameliorated the negative effects of salinity on plant growth and fruit yield. Treatment 4 (C+S+CaN) was slightly more effective in mitigating salt stress than treatment 5 (C+S+KN). However, neither of these was as effective as the combined treatment 6. Membrane permeability increased with high NaCl and was reduced by supplementary Ca(NO) and KNO. Sodium concentration in plant tissues increased in both cultivars in the high NaCl treatment. Leaf concentrations of calcium (Ca), potassium (K), and nitrogen (N) were much lower in plants grown at high NaCl than those in the unstressed treatment (C). Concentrations of these three nutrients were all significantly increased by both individual supplements but were generally highest, in some cases very close to control values in the C+S+CaN+KN treatment.