Physiological alterations in ‘Rubinela’ lettuce (Lactuca sativa L.) cultivated in conventional and hydroponic systems

Lettuce (Lactuca sativa L.) is the most consumed leafy vegetable in Brazil. It is cultivated using at least four distinct systems, the most common of which are conventional and hydroponic systems. These systems provide different cultivation conditions for plants, causing physiological changes that are important for commercial production, such as nutrient uptake and biomass accumulation. However, only a few studies have compared the physiological aspects of these two cultivation systems. The objective of this study was to evaluate the physiological behavior of ‘Rubinela’ lettuce plants grown in hydroponic and conventional pot systems, by comparing dry mass (DM) and fresh mass (FM) production, number of leaves (NF), stomatal density, and contents of chlorophyll, carotenoids, anthocyanin, sugars, and starch. Plants cultivated in hydroponic systems presented significant differences in chlorophyll content, producing more biomass than plants cultivated in conventional pot systems, probably because of better nutritional conditions, primarily with respect to macronutrients, provided by the nutrient solution of the hydroponic system. The lower water availability encountered by plants cultivated in conventional pot systems influenced the increased sugar and starch concentrations, as well as the anthocyanin content, which may be a strategy to mitigate the possible damage caused by hydric stress conditions.