Physiological permanent wilting point and osmotic potential of cowpea grown in saline soils/Ponto de murcha permanente fisiologico e potencial osmotico de feijao caupi cultivado em solos salinizados

In order to evaluate the physiological wilting point, the moisture content and leaf osmotic potential in cowpea, two experiments were carried out in a greenhouse of the Federal Rural University of Pernambuco (Recife, PE, Brazil). Two stress conditions were evaluated: salinity and salinity + water stress. The experimental design was completely randomized, in factorial arrangement of 2 x 4, composed of two classes of soil texture and four levels of soil salinity (control, 4, 8 and 12 dS [m.sup.-1]), with five replications. The species cowpea [Vigna unguiculata L. (Walp.)], cultivar Pele de Moca was used as test crop. It was concluded that the permanent wilting point of cowpea is smaller when determined by the physiological method than by Richards chamber method; the increase in soil salinity ([CE.sub.es]) up to 12 dS [m.sup.-1] does not influence the leaf moisture content, regardless of soil texture; and the leaf osmotic potential of cowpea decreases with the increasing soil salinity, which can be used as an important variable in saline environments.