Effect of growth stages on phenolics content and antioxidant activities of shoots in sweet marjoram (Origanum majorana L.) varieties under salt stress

We investigated the contributions of salinity and development stage on total polyphenols, flavonoids,  condensed tannins contents, phenolic content, 1,1-diphenyl-2-picrylhydrazyl (DPPH) and superoxide  scavenging activities at three phenolic stages: early vegetative stage (EVS), late or prefloral vegetative (LVS) stage and flowering stage (FS). The total phenolic, flavonoids and condensed tannins contents were more  important in the presence and absence of salt at prefloral or building stage than at EVS and FS. In addition, salt stress increased total polyphenol and individual phenolic contents in shoots of Origanum majorana. This  increase was more important in LVS than in EVS and FS. Moreover, the antiradical activity of the shoots (DPPH) decreased with the addition of NaCl. In fact, LVS extracts showed the highest antioxidant properties.  Furthermore, at LVS, marjoram grown at 75 mM showed a higher antiradical ability against DPPH radical and antioxidant activity, compared to EVS and LVS. Data reported here revealed the variation of phenolic  compound contents at different stages of growth of O. majorana, and the possible role of these changes in the response of the plant to salt was also discussed.Key words: Antiradical activity, Origanum majorana, early vegetative stage (EVS), late or prefloral vegetative (LVS) stage and flowering stage (FS), phenolic content

Salt effects on trichome density in Ocimum basilicum L. leaves

Effects of equimolar concentrations of NaCl and Na2SO4 on trichome morphology and distribution were studied in Ocimum basilicum. Plants were treated with high salinity for 15 days. Under control conditions, four types of trichomes were observed, two non glandular trichomes (NGT, bicellular or multicellular) and two glandular trichomes (GT; peltate, P and capitate, C). In contrast with P, NGT were more represented on the adaxial than on the abaxial leaf side whereas the density of C ones was not significantly affected by the surface. Under salinity conditions, the density of P trichomes increased if plants were treated with 50 mM NaCl whereas an opposite pattern was observed following 25 mM Na2SO4 treatment. Changes in GT density under salinity was correlated with their role in essential oil production. However, the density of C, which is not considered being involved in this role, decreased regardless to the type of salt administered