Productive and physiological performance of lettuce cultivars under hydroponic cultivation in the semi-arid region of the Northeast

Lettuce is the most-produced leafy vegetable in Brazil; however, to achieve satisfactory production in the different regions, it is necessary to choose the correct cultivar. The aim of this work was to evaluate the productive and physiological performance of lettuce cultivars in a hydroponic system located in Caucaia, in the state of Ceará. A completely randomised design was used, with four cultivars (Isabela, Vanda, Elba and Summer Crisp) and four replications. The following were evaluated: plant height and diameter (PH and PD), total fresh and dry weight (TFW and TDW), commercial fresh weight (CFW), internal CO2 concentration (Ci), stomatal conductance (gs), photosynthesis (A), ratio between internal and external CO2 concentration (Ci/Ca), and transpiration (E). Differences were seen between cultivars in the production and physiological characteristics, except for Ci and Ci/Ca. The ‘Elba’ and ‘Summer Crisp’ cultivars were the first to show signs of bolting (32 and 36 days) and greater height, 38.7 and 31.8 cm respectively. The ‘Isabela’ and ‘Vanda’ cultivars obtained the greatest values for CFW (43.5 and 41.13 g) and TFW (49.38 and 46.46 g). In relation to physiological performance, the ‘Isabela’ and ‘Summer Crisp’ cultivars presented the most photosynthesis. The ‘Isabela’ cultivar had the best productive and physiological performance, in addition to being the only cultivar that presented no signs of bolting, and is therefore strongly suggested for hydroponic production under the conditions of this study.