Abstract
The effect of irrigation with increasing concentrations of salt [4.5 (control), 25,50,75, 100,150, and 200 mM] on shoot growth and the essential oil (EO) composition of Rosmarinus officinalis L. was investigated in 27year-old plants growing on dune-sand in pots. Shoot extension was riot affected by low NaCl concentrations in the soil solution (<= 25 mM); but it decreased with higher concentrations. NaCl at 150 mM and 200 mM was lethal and caused the plants to wilt after 1 month of culture. The Na+ content of both leaves and roots increased, whereas the K+ content decreased with the progressive increase in NaCl concentration in the growth medium. Rosemary plants maintained a higher K+:Na+ ratio in the shoots compared to roots. It appeared that rosemary is moderately salt tolerant. This tolerance is apparently due to the ability of these plants to accumulate Na+ in their old leaves and to maintain a higher K+: Na+ ratio in the leaves compared to the roots. During the period of study, the level of salinity in the soil solution affected the EO composition. There was a 50% decrease in the content of 1,8-cineole with increasing NaCl concentrations, concomitant with a slight increase in borneol content.