Volatile diterpene emission by two Mediterranean Cistaceae shrubs

Area of Science:

• Atmospheric Chemistry
• Plant Physiology
• Ecology

Background:

• Mediterranean vegetation is a major source of biogenic volatile organic compounds (BVOCs).
• Isoprenoids are the most abundant class of BVOCs emitted by these plants.
• Diterpenes, like kaurene, have been less studied in terms of their atmospheric emissions compared to other isoprenoids.

Purpose of the Study:

• To investigate and quantify kaurene emissions from two Mediterranean Cistaceae shrubs: Halimium halimifolium and Cistus ladanifer.
• To determine the emission patterns and potential sources of kaurene.
• To assess the atmospheric significance of diterpene emissions from Mediterranean ecosystems.

Main Methods:

• Real-time detection of diurnal kaurene emission patterns using Proton-Transfer-Reaction-Time-of-Flight-Mass-Spectrometry (PTR-TOF-MS).
• Controlled laboratory experiments and natural field measurements.
• ¹³C-pyruvate labeling experiments to trace biosynthetic pathways.

Main Results:

• Kaurene emissions were detected in real-time, showing significant variability among individuals of H. halimifolium.
• Emission rates of kaurene were comparable to those of monoterpenes and sesquiterpenes.
• ¹³C-pyruvate labeling indicated that kaurene emissions are not from de novo biosynthesis, suggesting release from storage pools, especially at higher temperatures.

Conclusions:

• Mediterranean shrubs emit substantial amounts of kaurene, a diterpene.
• Kaurene emission is likely driven by stored compounds rather than active synthesis.
• The atmospheric contribution of diterpenes warrants increased attention in future research.