Effect of salt stress on the growth of Lippia gracilis Schauer and on the quality of its essential oil

This study evaluated the effect of salt stress on the growth of Lippia gracilis Schauer, a species native to the caatinga (shrublands) of Brazil and rich in essential oils, as well as on the quality of its oil. We exposed individuals of L. gracilis to NaCl, in the following concentrations, for a period of 40 days: 25 mM; 50 mM; 75 mM; and 100 mM. An additional group of plants was not exposed to NaCl (controls). Data were collected on days 20 and 40. We evaluated relative growth rate; shoot and root dry weight; relative water content; proline concentration in leaves; and chemical composition of the essential oil. At all concentrations, NaCl reduced the relative growth rate in comparison with that observed for the controls. No significant difference in relative water content was observed among treatments. In all treatments, the proline concentration in leaves was highest on day 40. Salt stress did not affect the yield or the concentrations of the constituents of the essential oil of L. gracilis, carvacrol and thymol showing the highest concentrations in all treatments.