Effect of arsenic on trichome ultrastructure, essential oil yield and quality of <i>Ocimum basilicum</i> L.

Abstract

An experiment was carried out to study the effect of various arsenic (As) treatments on growth, essential oil (EO) yield, composition of oil and morphology and ultrastructure of glandular trichomes of Ocimum basilicum (sweet basil) an important EO yielding plant. As in the form of disodium hydrogen arsenate [Na2HAsO4.7H2O] was added in the soil in the range of 0, 10, 50, 150 mg/kg As. As stress caused reduction in growth and biomass of shoot system at 50 and 150 mg/kg As. EO yield increased by 3.5-4 times at 10 and 50 mg/kg As, but decreased significantly by 0.08% at 150 mg/kg As. GC analysis revealed that linalool the main EO compound present in the leaves augmented 3 to 4 times under 10-150 mg/kg As as compared to control. Other compounds such as 1,8-cineol and methyl eugenol decreased with increased As treatments whereas methyl cinnamate was not detected at 50 and 150 mg/kg As in chromatographs. Camphor did not appear in any of the As treated plants. Light microscopic studies and electron micrographs revealed that As stress affected glandular trichome morphology and ultrastructure. Premature senescence was observed in trichomes of leaves at 150 mg/kg As and noticeable changes were observed in cell organelles of secretary cells. A positive correlation between EO yield and trichome density was observed in the present study.