Effect of light intensity and water availability on plant growth, essential oil production and composition in Rosmarinus officinalis L.

Abstract

The effect of light intensity (LI) and water availability (WA) on rosemary (Rosmarinus officinalis L.) plant growth, essential oil (EO) production and composition was investigated by a two-factorial field experiment, where the first factor was LI (100%, 50% or 25% of natural sunlight) and the second factor was WA (irrigation set at 85%, 70% or 55% of field capacity during plant growing). The EO obtained by steam distillation of the dried aerial part of the plant was analysed by GC/MS. Reduction of LI from 100 to 25% of natural sunlight markedly lowered plant biomass production, whereas reduction of WA from 85 to 55% had a smaller lowering effect on plant growth. High shading (25% of LI) markedly reduced EO yield on a plant basis (− 43%), whereas intermediate shading (50% of LI) increased EO yield as % content of the fresh biomass (+ 29%) when compared to full solar radiation. WA markedly influenced EO yield, as expressed on a plant basis, but only in plants exposed to 100% LI. Moreover, changes in LI and WA seemed to have an opposite effect on the relative abundance of EO constituents that are formed through the activity of two groups of enzymes, pinene synthases (α- and β-pinene, camphene and myrcene) and, respectively, bornyl diphosphate synthases (borneol, camphor and bornyl acetate). Accurate management of light conditions and water availability, in greenhouse as well as open field conditions, may allow to optimize rosemary EO yield and modulate EO profile in view of different potential uses.