Effect of cobalt salts on certain biological indicators of lettuce (Lactuca sativa L.) grown under hydroponic system

Abstract

Cobalt plays an essential role in plant metabolism and is considered a beneficial element at low concentrations for many plants. This study aimed to examine the impact of adding two types of cobalt salts, namely cobalt(II) sulfate heptahydrate (CoSO₄.7H₂O) and cobalt(II) nitrate hexahydrate (Co(NO₃)₂.6H₂O), on the levels of proline, malondialdehyde, protein, carbohydrates, and allantoin content in the leaves of lettuce, and Comparing different forms of cobalt salts and determining which are less harmful to lettuce plants grown under hydroponic system. The study found that adding cobalt salts led to an increase in the accumulation of proline and malondialdehyde in plant leaves. The highest value for both compounds was observed when cobalt nitrate was added at a concentration of 50 mg L^-1. However, the addition of both cobalt salts resulted in a decrease in the total protein content of lettuce plants. The lowest value was observed when treated with cobalt sulfate and cobalt nitrate at a concentration of 50 mg L^-1. Both cobalt salts also had an effect on the total carbohydrate content in the plant. The highest total carbohydrate content values were observed when treated with 30 mg L^-1 of cobalt nitrate. Also, the study found that cobalt salts had a significant effect on the allantoin content, as the highest value was observed at a concentration of 10 mg L^-1 of cobalt nitrate. Finally, using cobalt salts in concentrations lower than 10 mg L^-1 is recommended as higher concentrations are toxic to most biological indicators in lettuce.