Effect of Gibberellic Acid on Growth, Yield, and Quality of Leaf Lettuce and Rocket Grown in a Floating System

Gibberellins (GAs) are growth hormones strongly involved in a wide variety of physiological activities. Currently, gibberellins are commercially used to enhance phenotypic characteristics, earliness, and productivity of many vegetable and ornamental crops. In this work, the effcacy of supplementation of low levels of gibberellic acid (0, 10-8, 10-6, and 10-4 M GA3) through the mineral nutrient solution of a floating system on yield and quality of leaf lettuce and rocket plants was tested. The marketability of plants was lost when 10-4 M GA3 was added to the mineral nutrient solution. This study demonstrated that the addition of 104 M GA3 exceeded the acceptable threshold for use in hydroponics production systems. Below the concentration of 10-4 M, the presence of GA3 in the mineral nutrient solutions (MNS), especially at 10-6 M GA3, stimulated plant growth and enhanced the yield. Various morphological and physiological traits were enhanced by GA3 treatments (biomass accumulation, leaf expansion, stomatal conductance, water use eciency (WUE), Nitrogen use eciency (NUE), etc.), with superimposable trends in both lettuce and rocket. The addition of 10-6 M GA3 to the nutrient solution of a hydroponic floating system can promote growth and quality of lettuce and rocket plants.