Understorey Rhododendron tomentosum and Leaf Trichome Density Affect Mountain Birch VOC Emissions in the Subarctic

Adedayo O Mofikoya,Rajendra P Ghimire,Toini Holopainen,James D Blande,Kazumi Miura,Minna Kivimäenpää,Jarmo K Holopainen

doi:10.1038/s41598-018-31084-3

Adedayo O Mofikoya, Rajendra P Ghimire + Show 5 more

Open Access

https://doi.org/10.1038/s41598-018-31084-3

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Journal: Scientific Reports	Publication Date: Sep 5, 2018
Citations: 18	License type: open-access

Affiliation: University of Eastern Finland

Abstract

Subarctic vegetation is composed of mountain birch [Betula pubescens ssp. czerepanovii (MB)] forests with shrubs and other species growing in the understorey. The effects of the presence and density of one understorey shrub, Rhododendron tomentosum (RT), on the volatile emissions of MB, were investigated in a Finnish subarctic forest site in early and late growing season. Only MB trees with an RT-understorey emitted the RT-specific sesquiterpenoids, palustrol, ledol and aromadendrene. Myrcene, which is the most abundant RT-monoterpene was also emitted in higher quantities by MB trees with an RT-understorey. The effect of RT understorey density on the recovery of RT compounds from MB branches was evident only during the late season when sampling temperature, as well as RT emissions, were higher. MB sesquiterpene and total emission rates decreased from early season to late season, while monoterpene emission rate increased. Both RT and MB terpenoid emission rates were linked to density of foliar glandular trichomes, which deteriorated over the season on MB leaves and emerged with new leaves in the late season in RT. We show that sesquiterpene and monoterpene compounds emitted by understorey vegetation are adsorbed and re-released by MB, strongly affecting the MB volatile emission profile.

Highlights

Plant-emitted VOCs mediate a number of ecological interactions including plant-to-plant interactions[11], where VOCs emitted by a plant may affect neighbouring plants via passive or active means
Total mountain birch (MB) emissions were highest in the Non-RT control group (NRT) group in June 2017, the same trend was observed in June 2015 and August 2017 (Fig. 3A,B)
Our results demonstrate the adherence and re-release of R. tomentosum (RT) VOCs by neighbouring mountain birch (MB) trees in the subarctic

Summary

Introduction

Plant-emitted VOCs mediate a number of ecological interactions including plant-to-plant interactions[11], where VOCs emitted by a plant may affect neighbouring plants via passive or active means. Passive adsorption and re-release of neighbouring plant VOCs has been reported to increase resistance to herbivores in boreal ecosystems[14] and is dependent on the distance between the emitter and receiver plant and the air temperature[14,16]. RT is a woody perennial evergreen shrub distributed throughout boreal and subarctic ecosystems[14] We observed that it is characterized by a dense distribution of glandular trichomes on stem and leaf surfaces (Fig. 1), and has a characteristic smell resulting from a high terpenoid content[24]. The temperature dependence of plant terpenoid emissions[4] as well as adsorption and re-release of VOCs by neighbouring plants[16] makes studying the process in the subarctic relevant. These temperature changes may result in a change in plant species composition and subsequently the quality and quantity of VOC emission profiles in the regions

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