Interactive Effects of Gibberellin Application and Shading Regimes on The Growth and Yield of Red Lettuce (Lactuca sativa L.) in Verticulture System

Background:. Red lettuce (Lactuca sativa var. Arista) cultivated in lowland areas often experiences growth constraints due to high temperature and excessive light intensity, resulting in reduced productivity. The application of gibberellin and shading is considered a potential strategy to improve plant growth and yield under these conditions. Methodology: This study aimed to evaluate the interaction between gibberellin concentration and shading percentage on the growth and yield of red lettuce cultivated using a vertical farming system. This study was conducted in Paji Village, Pucuk District, Lamongan Regency, at an elevation of 7 meters above sea level, with temperatures ranging from 24°C to 34°C and an average rainfall of 8–25 mm per month. A split-plot design with three replications was used, with shading levels of 0%, 50%, and 75% as main plots and gibberellin concentrations of 0, 50, 100, and 150 ppm as subplots. Data were analyzed using ANOVA, followed by a 5% HSD test when significant differences were detected. Findings: Significant interactions between gibberellin concentration and shading percentage were observed for plant height, leaf number, leaf area, and fresh canopy weight. Gibberellin concentration significantly affected harvest index, whereas shading significantly affected leaf color. The combination of 100 ppm gibberellin and 75% shading produced the highest growth and yield, while harvest index and leaf color were not significantly affected by the interaction. Contribusions: This study provides practical guidance for optimizing gibberellin concentration and shading to enhance red lettuce growth and yield in vertical farming systems, supporting urban agriculture practices in lowland areas