EFFECTS OF CALCIUM AND SALINITY STRESS ON QUALITY OF LETTUCE IN SOILLESS CULTURE

Abstract

Lettuce (Lactuca sativa L.) var. ‘Lollo rossa’ was grown in a floating hydroponic system. Six saline treatments were used, adding different concentrations of calcium chloride (CaCl₂) to the nutrient solution (mol m⁻³): 0, 2.5, 5, 10, 15, 20, which, respectively, corresponds to an electrical conductivity of 2.5, 3, 3.5, 4.4, 5.4, 6.3 dS m⁻¹. In plants subjected to moderate salinity stress the growth was not affected and yields were not statistically significant; however, the data shows a slight decline in 20 mol m⁻³ CaCl₂ treatments. Nitrate contents in the leaf decreased when the concentration of CaCl₂ in nutrient solutions increased. Other quality parameters were positively affected by treatment with CaCl₂, especially at moderate concentrations such as 5 and 10 mol m⁻³. In fact, both the content of phenols and antioxidant power increased at moderate salt concentrations and reduced in the treatment with 20 mol m⁻³ CaCl₂. The content of chlorophyll and carotenoids were not affected by treatment even at high salt concentrations. The use of CaCl₂ did not result in nutrition imbalances in plants either. In fact, the ratio K/Na remained unchanged in the various treatments, as well as the contents of microelements.

Keywords:

• floating system
• leafy lettuce
• Lactuca sativa L.
• calcium chloride
• antioxidant capacity
• ABA