Effects of different nutrient solution concentrations on the growth and nitrate accumulation of hydroponic lettuce

Effects of four different nutrient solution concentration treatments(1/4, 1/2, 1 and 2 units of Yamasaki lettuce nutrient solution formula) on the growth and nitrate accumulation of lettuce(cv. Hongnong and Lvling) were investigated. The results showed that shoot and root fresh weights, leaf length and width were the biggest in the 1/2 unit nutrient solution treatment, whereas they were the least in the treatment of 2 unit nutrient solution. The accumulation of nitrate in the lettuce leaves in different nutrient solution treatments was 2s>1s>1/2s>1/4s, and the SOD activity and MDA content in lettuce leaves were the highest in the treatment of 2 unit nutrient solution. The nitrate content in the leaves increased significantly with the concentration of nutrient solution, and the highest nitrate content, soluble protein content and soluble sugar content were in the treatment of 2 unit nutrient solution. It was suggested that 1/2 unit of Yamasaki lettuce nutrient solution formula was the most economic nutrient solution formula suited for lettuce hydroponic production.