Seeds of Ocimum basilicum cv. keskenylevelu provided from Hungary, were used in this study. Potted seedlings of Ocimum basilicum were subjected to study the effect of different irrigation rigimes on the essential oil content and composition at experimental farm of college of agriculture, Tarbiat Modarres, University, located in Tehran. (1215 m above sea level, latitude 35° 43′ north, altitude 51° 8′ east). The seeds were sown in spring of 2001 in pots. The irrigation regimes to induce of water stress were: 100%, 85%, 70% and 55% of field capacity. This percentage of field capacity kept constant in the soil by daily weighting of pots. The soil was sandy-loam with 22.6% of field capacity. The harvest of whole plants was performed at the beginning of the flowering stage.

The essential oil content of herb increased from 1.12 to 1.26% as plant water deficit increased (till 70% of field capacity). The number of component of the oil of Ocimum basilicum increased as water stress increase. Amount of the main constituents of the oil such as linalool, methyl chavicol, 1,8-cineole and trans alpha-bergamotene significantly affected by water stress.

The aerial parts (~35 cm) of each taxa growing wild in eight localities of Almeria province were collected in May 1996. All samples were collected at full flowering. Sideritis pusilla (Lange) Pau ssp. pusilla var. typica, Population/location (UTM): Los Matarines (30SWF7992); Sideritis pusilla ssp. pusilla var. carthaginensis Font Quer, Population/location (UTM): Rambla del Hacho (30SWF7178); Sideritis pusilla ssp. pusilla var. granatensis (Pau) Font Quer, Population/location (UTM): Gafarillos (30SWG8702); Sideritis pusilla ssp. almeriensis (Pau) Malagarriga var. typica, Population/location (UTM): Sierra de Gador, Cerro de los Lobos (30SWF3575); Sideritis pusilla ssp. almeriensis var. littoralis Font Quer, Population/location (UTM): Los Morales (30SWF6775); Sideritis pusilla ssp. almeriensis var. salina Font Quer, Population/location (UTM): Los Pedregales (30SWG7835); Sideritis pusilla ssp. flavovirens (Rouy) Malagarriga, Population/location (UTM): Velez Rubio, Cerro del Huezno (30SWG8965); Sideritis pusilla ssp. osteoxylla (Pau) Pallares, Population/location (UTM): Cabo de Gata, Cerro de S. Miguel (30SWF7165)

Monoterpene hydrocarbons, alcohols, sesquiterpenes and diterpenes were the main constituents in all samples. Among these, alpha-pinene (7.1-25.4%), sabinene (5.9-20.4%), fenchone (0.9-19.3%), limonene (1.2-7.4%) and 1,8-cineole (1.8-15.6%) were the major compounds. The results confirm that there are differences between varieties and subspecies, while cluster analysis revealed that the oil composition potentially has chemotaxonomical significance for this taxon.