Abstract

Lettuce (Lactuca sativa L.) is considered as the main leafy vegetable in Brazil. In the last decades, there had been many changes in the predominant varietal types in the country, however, issues regarding the use of saline water inhibit the growth by the osmotic effect. The aim of this study is avaliate the effect of water salinity on physiological in lettuce cultivars. The experiment was carried out at the Alagoas Federal University, Arapiraca Campus, in a completely randomized design and with a 5 × 2 factorial scheme, with six replications. Five treatments of water salinity levels were analyzed (ECw: 0.14, 1.54, 2.94, 4.34, and 5.74 dS m^-1 at 25 °C) in two types of lettuce crops (Saia Véia and Vitoria Verdinha). Stomatal conductance, net photosynthesis, transpiration rate, water use efficiency, leaf temperature, and green index were assessed at 10, 20, and 30 days after the application of the treatments. The saline stress caused by the increase in saline concentrations decreased the photosynthesis and transpiration rates, which were associated with the reduction of stomatal conductance in both cultivars. Nevertheless, Saia Véia cultivar was higher tolerance in all tested saline levels compared to Vitória Verdinha. The green index for Vitoria Verdinha was seven times higher when compared to Saia Véia from the lowest to the highest saline levels. The cultivars differ in salt sensitivity, which could be useful for producers to choose the cultivar that is most adapted to the region and breeders regarding improvement prospects for adaptation of the lettuce under saline stress. In addition to osmotic stress, which is the first to happen, there are others.

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