Calcium improves the leaf physiology of salt treated Limonium stocksii: A floriculture crop

Abstract

Calcium acts as a signaling molecule in many plants to improve resistance during unfavorable environments. Limonium stocksii (Boiss.) Kuntze seedlings were grown in 0 and 600 mmol L−1 NaCl (with and without additional 15 mmol L−1 Ca2+) for 15 d. The effects of these treatments were studied on plant growth, leaf water relations, malondialdehyde (MDA) content, ion-flux, Na+ secretion rate and photosynthesis. Plant biomass declined by 50% and MDA content increased by 50% in plants treated with 600 mmol L−1 NaCl for 15 d. Leaf water content (WCFM) and relative water content declined and sap osmolality increased after 3 d of 600 mmol L−1 NaCl treatment. Leaf Na+, Na+/K+ ratios and Na+ secretion rate were increased in salinity treatment. Decrease in photosynthesis was coupled with lower stomatal conductance and intercellular CO2, however, instantaneous water use efficiency was improved under salinity treatment. Efficiency of PSII, relative electron transport rate, photochemical quenching and non-photochemical quenching were reduced by salinity treatment compared to non-saline control. The Ca2+ application yielded 25% higher fresh mass at enhanced water contents while lowers tissue osmotic potential and membrane damage in plants exposed to high salinity. The Na+ accumulation in the leaf was reduced, while the secretion was increased in the presence of additional Ca2+. However, Ca2+ application did not improve either the photosynthetic gas exchange or light reactions of photosynthesis under saline conditions. Our results indicated that L. stocksii decreases its growth, water content, photosynthesis and dark respiration under increased leaf Na+ concentrations. Whereas, application of Ca2+ enhanced plant salinity resistance by improving water balance, Na+-secretion and membrane integrity.