Three different altitudes were selected to study the variability of terpenoid composition from leaves of female plants of Pistacia lentiscus L. throughout the elevation gradient. GC-MS analyses showed that terpenoid contents change with altitude. Forty nine compounds were identified with a high interpopulation variability for low- and midaltitude sites that also exhibited the same major components when data were expressed on dry weight basis. However, Two-Way-ANOVA followed by Tukey’s post hoc test showed that monoterpene hydrocarbons increased with elevation, giving values of 21.7, 37.5 and 221.5 µg g−1 dw for low- mid- and highlands, respectively. On the other hand, applying P.C.A. with data expressed in percentage of the chromatogram of the volatile extract led to the identification of three chemotypes associated with altitudinal levels. In highlands (Group I), the major compounds were β-caryophyllene (12%), δ-cadinene (9.3%) and α-pinene (6.3%) while in midlands (Group II), β-caryophyllene (11.5%), δ-cadinene (8.6%) and caryophyllene oxide (6.8%) were the main components. In lowlands (Group III) δ-cadinene (10.9%), cubebol (10.5%) and β-bisabolene (7.7%) were chiefly present. Hence, the involvement of genetic factors, temperature and drought in the chemical polymorphism of P. lentiscus associated with elevation is discussed in this report.

a b s t r a c tThree Algerian populations of female Pistacia atlantica shrubs were investigated in order to check whether their terpenoid contents and morpho-anatomical parameters may characterize the infraspecific variability. The populations were sampled along a gradient of increasing aridity from the Atlas mountains into the northwestern Central Sahara.As evidenced by Scanning Electron Microscopy, tufted hairs could be found only on seedling leaves from the low aridity site as a population-specific trait preserved also in culture. Under common garden cultivation seedlings of the high aridity site showed a three times higher density of glandular trichomes compared to the low aridity site. Increased aridity resulted also in reduction of leaf sizes while their thickness increased. Palisade parenchyma thickness also increases with aridity, being the best variable that discriminates the three populations of P. atlantica.Analysis of terpenoids from the leaves carried out by GC-MS reveals the presence of 65 compounds. The major compounds identified were spathulenol (23 g g −1 dw), ␣-pinene (10 g g −1 dw), verbenone (7 g g −1 dw) and ␤-pinene (6 g g −1 dw) in leaves from the low aridity site; spathulenol (73 g g −1 dw), ␣-pinene (25 g g −1 dw), ␤-pinene (18 g g −1 dw) and ␥-amorphene (16 g g −1 dw) in those from medium aridity and spathulenol (114 g g −1 dw), ␣-pinene (49 g g −1 dw), germacrene D (29 g g −1 dw) and camphene (23 g g −1 dw) in leaves from the high aridity site. Terpene concentrations increased with the degree of aridity: the highest mean concentration of monoterpenes (136 g g −1 dw), sesquiterpenes (290 g g −1 dw) and total terpenes (427 g g −1 dw) were observed in the highest arid site and are, respectively, 3-, 5-and 4-fold higher compared to the lower arid site. Spathulenol and ␣-pinene can be taken as chemical markers of aridity. Drought discriminating compounds in low, but detectable concentrations are ␦-cadinene and ␤-copaene. The functional roles of the terpenoids found in P. atlantica leaves and principles of their biosynthesis are discussed with emphasis on the mechanisms of plant resistance to drought conditions.