Effects of NaCl application to hydroponic nutrient solution on macro and micro elements and protein content of hot pepper (Capsicum annuum L.)

Growth and nutrient acquisition of pepper (Capsicum annuum L.) cv. Bonanza were studied under salt stress in Hoagland’s solution. The plants were treated for 23 days with salinity induced by incorporating different concentrations (0.0 (control), 50, 100, 150 or 200 mM) of NaCl to the nutrient solution. At harvest, shoot biomass, shoot length, fresh weight and dry weight of shoot and root were determined. Slight reduction was obtained in growth represented by shoot length and number, leaf number and dry weight when seedlings were directly exposed to NaCl stress from 0.0 to 100 mM. At higher concentrations (150 or 200 mM), growth parameters were adversely affected and seedlings died thereafter. Relative water content (RWC) of the plant decreased under saline conditions in both shoots and roots. Compared to the control, the relative water content (RWC) in the shoots and roots of pepper decreased by 7.2% for shoots and 14.8% for roots at 200 mM NaCl level, respectively. The total crude protein content of plants was substantially lower under salt stress as compared with the control. Elevated salinity significantly reduced crude protein in shoots and roots as well. Mineral elements K, P, N, Na, Fe, Zn, Cu and Mn in shoot and root were also analyzed. Increasing salinity levels reduced the uptake of N, P, K and Fe, and increased Na, Mn, Cu and Zn contents. Salinity changes the available concentration of these elements in soils due to an increase in the solubility of micronutrients under saline conditions. Reduction in pepper growth as a result of salinity may be attributed to ion toxicity associated with excessive uptake of Na. Pepper is susceptible and cannot survive under conditions of high salinity or can survive but with decreased yield.