Salt effects on the growth, mineral nutrition, essential oil yield and composition of marjoram (Origanum majorana)

The aim of this work was to investigate the growth, mineral nutrition and essential oil composition of marjoram aerial part. Seedlings were cultivated for 20 days on nutrient solution, and then transferred to hydroponic solution with different NaCl concentrations (0, 50, 100, 150 mM). Plants were harvested after 17 days of treatment. Mineral nutrition and essential oil composition of shoots were determined. Results showed that growth, water content and development of the different organs of marjoram plant were affected just at the highest NaCl concentration (150 mM). Furthermore, salt did not seem to affect leaf area and root length but reduced the number of leaves. An increase in the total leaf surface and its thickness was observed at different NaCl concentrations. At 50 mM NaCl, sodium was primarily accumulated in roots but at 150 mM, it was strongly accumulated in leaves. However, Cl(-) accumulation was lower at higher NaCl concentrations. Essential oil yield of marjoram shoots was 0.12% in the control and 0.10% at 50 mM but an important decrease was observed at 100 mM (0.05%). Thirty-three components were identified belonging to different chemical classes. In the control, the essential oil was found to be rich in trans-sabinene hydrate (47.67%), terpinen-4-ol (20.82%) and cis-sabinene hydrate (7.23%). The proportions of these main compounds were differently affected by salt.