Calcium effects on changes in chlorophyll contents, dry weight and micronutrients of strawberry (Fragaria x ananassa Duch.) plants under salt-stress conditions

Introduction. Today, approximately one-third of the world's irrigated lands suffer some degree of salinity. Although there are several reports about the effects of calcium treatments on strawberry growth and development under saline conditions, there are no reports demonstrating the effect on micronutrient concentrations of strawberry due to supplementary calcium applied to the salt-stressed plants. Consequently, we investigated the effects of high salinity levels, with application of supplementary calcium, on chlorophyll contents, dry weight and micronutrients of strawberry. Materials and methods. Strawberry (Fragaria x ananassa Duch.) plants cv. 'Selva' were grown in hydroponic culture in a heated greenhouse to investigate the effectiveness of calcium (Ca) added to nutrient solution applied to plants. Six treatments were applied: nutrient solution alone (= [N]); [N] + NaCl salt (35 mM) (= [NS]); [NS] + CaCl2 (5 mM); [NS] + CaCl2 (10 mM); [NS] + CaSO4 (5 mM); and [NS] + CaSO4 (10 mM). The effect of calcium (different forms and different concentrations) on chlorophyll contents and dry weight of salt-stressed plants was determined. Additionally, micronutrient contents were studied. Results. The results indicated that chlorophyll contents and plant dry weight were decreased by salinity. NaCl application increased Cu, Zn, Mn and Fe concentrations of root parts. In shoot parts, Cu accumulation decreased, while other elements increased. Supplementary calcium could ameliorate the negative effects of salinity on chlorophyll and dry mass production. However, micronutrient concentrations of plant parts as influenced by calcium had contradictory results: calcium induced high levels of zinc, manganese and iron concentrations in roots, but high levels of copper and zinc concentrations in shoots. Moreover, there were significant differences between calcium forms in their actions. Conclusion. Our results suggest that CaSO4 could be applied to improve the growth of salt-stressed strawberry plants.