Estresse salino na germinação, fase de muda e produção de alface (Lactuca sativa L.).

Abstract

The inadequate management of the irrigation may cause accumulation of soluble salts in soils which affects almost always negatively most of the crops, above all, the vegetables that are sensitive to the saline stress. Studies on tolerance of salinity on locally grown lettuce (Lacluca saliva L.) cultivars are inexistent; in that sense, two experiments were conducted with cultivar of lettuce 'Elba', the most planted in Campina Grande/PB region. In Experiment I, accomplished in greenhouse, in a completely randomized design the effect of six levels of salinity of the irrigation water - ECw (0.3, 1.0, 1.7, 2.4, 3.1 and 3.8 dS.m"1) was studied on the germination, vigor, scion and production of lettuce. In the second experiment, conducted in pots under plastic protection, also in a completely randomized factorial 5x2 design, effects of five levels of ECw (0.3, 1.0, 1.7, 2.4, 3.1 dS.m"1) in scion of lettuce 'Elba', produced under low (ECw 0.3 dS.m"1) and high (ECw 3.1 dS.m"1) salinity conditions were tested from transplanting to harvest. In the irrigation waters the equivalent proportion of Na:Ca:Mg was maintained as 7:2:1 respectively. The results obtained allow to affirm that in the germination of lettuce, the salinity affects more the vigor index (VI) than the percentage of germination (PG), the critical values of ECw, which cause decrease in PG and VI, compared to lowest level of salinity (0.3 dS.m"1) are of 2.81 and 2.42 dS.m"1, respectively, the vegetative growth of the aerial parts decreased linearly with the increase of ECw above 0.3 dS.m"1; the effect of the salinity, in the beginning and in the end of the growth cycle were found to be more intense on the roots, but in scion phase the effects were more severe on the aerial parts. The use of water of EC of 3.1 dS.m"1 in scion production did not show posterior influence on lettuce production though inhibited the root growth. The production of studied cultivar decreases 9% for each unit increase of ECw. Based on concept of relative decrease of production (value b), for unit increase of soil salinity (ECse), such decrease was 6.1%, it is concluded that cultivar 'Elba' of lettuce, under the conditions of the present study has higher tolerance to the salinity than that reported in the literature.