Production and Diversity of Volatile Terpenes from Plants on Calcareous and Siliceous Soils: Effect of Soil Nutrients
Résumé
Fertilizer effects on terpene production have been
noted in numerous reports. In contrast, only a few studies have
studied the response of leaf terpene content to naturally
different soil fertility levels. Terpene content, as determined
by gas chromatography/mass spectrometry/flame ionization
detector, and growth of Pinus halepensis, Rosmarinus
officinalis, and Cistus albidus were studied on calcareous
and siliceous soils under field conditions. The effect of
nitrogen (N) and extractable phosphorus (PE) from these
soils on terpenes was also investigated since calcareous soils
mainly differ from siliceous soils in their higher nutrient
loadings. Rich terpene mixtures were detected. Twenty-one
terpenes appeared in leaf extracts of R. officinalis and C.
albidus and 20 in P. halepensis. Growth of all species was
enhanced on calcareous soils, while terpene content showed
a species-specific response to soil type. The total monoterpene
content of P. halepensis and that of some major compounds
(e.g., δ-terpinene) were higher on calcareous than on
siliceous soils. A significant and positive relationship was
found between concentration of N and PE and leaf terpene
content of this species. These findings suggest that P.
halepensis may respond to an environment characterized by
increasing soil deposition, by allocating carbon resources to
the synthesis of terpene defense metabolites without growth
reduction. Results obtained for R. officinalis showed high
concentrations of numerous major monoterpenes (e.g., myrcene,
camphor) in plants growing on calcareous soils, while
α-pinene, β-caryophyllene, and the total sesquiterpene content
were higher on siliceous soils. Finally, only alloaromadendrene
and δ-cadinene of C. albidus showed higher concentrations
on siliceous soils. Unlike P. halepensis, soil nutrients
were not involved in terpene variation in calcareous and
siliceous soils of these two shrub species. Possible ecological
explanations on the effect of soil type for these latter two
species as well as the ecological explanation of rich terpene
mixtures are discussed.