Abstract
Plants produce specific terpenes, secondary metabolites conferring tolerance to biotic and abiotic stresses. Our study aims to investigate the effects of altitude, light intensity and season on contents of mono- and sesquiterpenes in needles of coniferous Norway spruce (Picea abies). Needles of current shoots representing upper and lower canopy were collected from adult trees growing along an altitudinal gradient (400–1100 m a.s.l.) in summer and autumn. After the extraction in cold heptane, the content of extractable terpenes was determined by gas chromatography coupled with mass spectrometry. Our results show that the total content of terpenes decreases with increasing altitude regardless of canopy position and season. Needles of the upper canopy have a higher total content of terpenes than lower canopy needles, but this difference decreases with increasing altitude in summer. Total content of extractable terpenes increases in autumn when compared to summer particularly in upper canopy needles of trees from high altitudes. Limonene, camphene, α-pinene and myrcene are the most abundant monoterpenes in spruce needles forming up to 85% of total monoterpenes, while germacrene D-4-ol is the most abundant sesquiterpene. Altitude, canopy position and season have a significant interactive effect on most monoterpenes, but not on sesquiterpenes. Terpenoid biosynthesis is thus tightly linked to growth conditions and likely plays a crucial role in the constitution of stress tolerance in evergreen conifers.
Highlights
All compounds detected are shown in Appendix A Table A1
Contents of some monoterpenes were substantially reduced at the highest altitude or completely disappeared (Appendix A)
We have found that the total content of terpenes increases from summer to autumn, due to increases in contents of camphene, α-pinene and myrcene
Summary
Environmental conditions such as precipitation, temperature, sky turbidity, intensity of solar radiation and/or nutrient availability vary along altitudinal gradients [1,2]. Physiological and biochemical plant traits change to ensure the adaptation and survival of plant species in different altitudes. Previous studies reported altitude-induced changes in leaf mass per area [3], stomatal density [4], CO2 assimilation rate and Rubisco carboxylase activity [5,6], and/or production of secondary metabolites [7]. Altitudinal studies enable the identification of the most relevant environmental factors affecting plant communities and mechanisms involved in plant acclimation and adaptation responses to environmental conditions
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