Calcium induces salinity tolerance in pistachio rootstocks

Introduction. Saline soils may exert a different effect on seed germination and seedling growth. Materials and methods. The seeds of two rootstocks of pistachio (Pistacia vera), Ghazvini and Badami-e-zarand, were incubated at 20 °C in the dark in a 150 mM NaCl solution or in 150 mM NaCl solutions amended with (50, 100 and 150) mM CaSO4. Seeds were planted in pots containing a mixture of garden soil, sand and compost (1/3 v/v) to investigate the effect of calcium sulphate on plants grown under salt stress. Irrigation water treatments were control (deionised water alone); salinity stress (150 mM NaCl); salinity with 50 mM CaSO4; salinity with 100 mM CaSO4; and salinity with 150 mM CaSO4. Results and discussion. In all treatments, both the final germination percentage and the final percentage of seeds with emerging seedlings longer than 20 mm were higher in the Ghazvini rootstock than in the Badami-e-zarand rootstock. Both the final germination percentage and the final percentage of seeds with emerging seedlings were significantly increased with increasing CaSO4 concentration, except at the highest CaSO4 concentration. The plants grown under 150 mM NaCl produced less dry matter and had lower chlorophyll content than those grown without NaCl. Supplementary CaSO4 only at (50 and 100) mM concentrations ameliorated the negative effects of salinity on plant dry matter and chlorophyll content. Sodium (Na) concentration in plant tissues increased in both leaves and roots of plants under the NaCl treatment alone. The Ghazvini rootstock had much lower Na. Additions of CaSO4 significantly lowered the concentration of Na in both leaves and roots. The Ghazvini rootstock was more tolerant to salinity than the Badami-e-zarand rootstock. The accumulation of Na in leaves and roots indicates a possible mechanism whereby cv. Ghazvini copes with salinity in the rooting medium, and/or may indicate the existence of an inhibition mechanism of Na transport to leaves. Concentrations of Ca and K were lower in the plants grown at high NaCl concentration than in those under the control treatment, and, for the cv. Ghazvini, these two element's concentrations were increased in both leaves and roots for the plants with calcium sulphate treatment; for the cv. Badami-e-zarand, these concentrations were increased in only the roots