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.