Callus inRosmarinus officinalisL. (Lamiaceae): A morphoanatomical, histochemical and volatile analysis

This study aims to evaluate the anatomy of calli and their chemico-morphological characteristics after in vitro culture. Callus was induced from leaf explants of Rosmarinus officinalis derived from in vitro grown plants on media containing 2,4-dichlorophenoxyacetic acid (2,4D) and thidiazuron (TDZ) supplementation. Both capitate and peltate glandular trichomes were recognized in R. officinalis callus by light and electron microscopy. Histochemical tests showed positive reactions to lipophilic and terpenoid compounds for capitate trichomes and parenchyma or meristematic cells. Volatiles were isolated by simultaneous distillation–extraction and analysed by gas chromatography. Specifically, the use of 2,4D was shown to have a positive effect on the capacity of R. officinalis friable callus to produce volatile monoterpene compounds relative to TDZ. The main volatiles produced by callus were α-pinene, β-pinene and camphor produced in media containing 0.5 and 1.0 mg L− 1 of 2,4D. Significant quantities of α-pinene, β-pinene and camphor were produced with 0.5 mg L− 1 of 2,4D. On the basis of this accumulated evidence, it can be concluded that R. officinalis callus produces volatiles in developing glandular trichomes and that cellular aggregates and in vitro culture can be used for the production of volatiles under in vitro controlled conditions from selected plant material.