Alleviation of salinity-induced stress in lettuce growth by potassium sulphate using nutrient film technique

Abstract

Salinity in soil, or irrigation water, can reduce plant growth, interfere with nutrient balance, and reduce crop yields. The effects of NaCl salinity and potassium level on the plant growth and severity of gray mold [Botrytis cinerea (De Bary) Whetzel] were investigated in lettuce (Lactuca sativa L. cvs. Beta and Paris Island) grown with the nutrient film technique (NFT) under greenhouse conditions during early spring. Plants were supplied with nutrient solutions containing 40 mM of sodium chloride (NaCl) and/or 10 mM potassium sulphate (K2SO4). Salinity or K-enrichment mainly affected the upper part of lettuce plants and reduced leaf fresh weight and leaf area. However, their combination reversed the negative impact of salinity on plant growth. Salinized and/or potassium-enriched plants did not differ in root length, leaf dry weight, leaf length, or numbers of leaves produced. Photosynthetic rate and the intercellular CO2 concentration did not differ among treatments, whereas stomatal conductance was reduced in salt-treated plants of cv. Paris Island. Salinity induced plant disease only for cv. Beta and greater disease severity was observed when salinity was combined with potassium. Total nutrient uptake was reduced 2-fold in salt-treated plants compared to controls. Lettuce grown in NFT had tolerance to NaCl salinity, and this method could be used to exploit saline water in soilless culture. These findings also suggest that a proper management of the salt concentration of the nutrient solution can provide an effective tool to improve the quality of leafy vegetables with little effect on yield.