Productive and physiological performance of lettuce cultivars at different planting densities in the Brazilian Semi-arid region

In regions of high temperature, production and quality in the lettuce is reduced. This requires finding of cultivars that are more adapted to such conditions and adjust the planting density for each cultivar. Consequently, the aim of this study was to evaluate the productive and physiological performance of lettuce cultivars at different planting densities under semi-arid conditions. The experiment was carried out at the Horticulture Teaching Garden of the Federal University of Ceara in Fortaleza, in a randomised block design with four replications, with the treatments arranged in a 4 × 4 factorial scheme. The first factor consisted of four lettuce cultivars (Red Salad Bowl, Salad Bowl Green, Mimosa Green Salad Bowl and Crespa Lollo Bionda) and the second factor of four planting densities (0.20 × 0.20 m, 0.25 × 0.25 m, 0.20 × 0.25 m 0.25 × 0.30 m between plants and rows). The characteristics of the lettuce such as qualitative (age at bolting and flowering, and state of health - pests and diseases), quantitative (plant height and diameter, fresh and dry commercial weight, fresh and dry non-commercial weight, and total fresh and dry weight), and physiological (gas exchange) were evaluated. The Salad Bowl Green and Mimosa Green Salad Bowl cultivars displayed average tolerance to bolting (63 days after sowing, DAS) and late flowering (95 DAS). ‘Salad Bowl Green’ had the highest total fresh and dry weight. For density, greater individual plant production was seen at 0.25 × 0.30 m; greater productivity of commercial fresh weight and total fresh weight was seen at 0.20 × 0.20 m for all cultivars. ‘Salad Bowl Green’ is the most promising for cultivation under semi-arid conditions when grown at lower densities. Key words: Lactuva sativa L., early bolting, productivity, dry weight, gas exchange.