Macquarie University
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On the physiology and evolution of volatile isoprenoid emission in plants

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posted on 2022-03-28, 11:03 authored by Srikanti Dani Kaidala Ganesha
Isoprenoid emission by plants (1 PgC/yr) via the chloroplast localised methyl-erythritol phosphate (MEP) pathway is a significant source of carbon that influences atmospheric oxidation chemistry and global carbon cycle. Despite significant progress in isoprenoid research, many deeper questions surround the biochemical regulation of the MEP pathway and the physiological adaptations of emitters that determine the observed diversity in emission rates, hindering our ability to estimate and forecast global emissions. In this thesis, we present the results of a comprehensive set of experiments on the physiology of isoprenoid emission in selected species of Eucalyptus, a diverse native Australian tree genus (>900 species) that is adapted to a wide ranging climate and habitats in Australia and emits both isoprene and monoterpenes at significant measurable quantities. Addressing some of the outstanding questions in complex interactive effects of abiotic stresses on isoprenoid emission, our experiments show how increased isoprenoid emission rate by plants under abiotic stresses (low CO2, heat and drought) is sustained by increased ratio of electron transport rate to net carbon assimilation rate. We also show how the MEP pathway competes with photorespiration for the residual reducing power not invested in carbon assimilation. Our results highlight the importance of species-specific tolerance for drought and provide a basis to observed variability and uncertainty in emission responses to drought. Tackling another important question pertaining annual cycles in emission, we establish an independent role for photoperiod in seasonal oscillations in emission. Experiments show that temperature entrains seasonal rhythms in isoprenoid emission rates and it is likely gated by a photoperiodic clock. Sensitivity of emission to photoperiod means that increasing global mean temperature could interfere with the photoperiod signaling pathway in major emitting tree genera, altering their seasonal emission responses. Using a comprehensive data set, we trace the patterns in the origin and evolution of isoprene emission in land plants and propose a novel hypothesis. We discuss various levels of natural selection acting on isoprenoid emission whilst we put the most important of our experimental results in a global perspective.


Alternative Title

Volatile isoprenoid emission in plants

Table of Contents

1. Introduction -- 2. Phtosynthesis and isoprene emission in eucalypts from contrasting environments -- 3. Paper 1: Increased ratio of electron transport to net assimilation rate supports elevated isoprenoid emission rate in eucalypts under drought -- 4. The curious case of post-illumination monoterpene burst (PiMB) -- 5. Paper 2: Seasonal rhythm of volatile isoprenoid emission in eucalypts is entrained by temperature and is photoperiod-gated -- 6. Paper 3: Evolution of isoprene emission capacity in plants -- 7. Paper 4: Biogenic volatile isoprenoid emission and levels of natural selection -- 8. Conclusion -- Appendices.


Includes bibliographical references Thesis abstract in English and in Kannada. Thesis by publication.

Awarding Institution

Macquarie University

Degree Type

Thesis PhD


PhD, Macquarie University, Faculty of Science, Department of Biological Sciences

Department, Centre or School

Department of Biological Sciences

Year of Award


Principal Supervisor

Brian J. Atwell


Copyright Kaidala Ganesha Srikanta Dani 2015. Copyright disclaimer:




1 online resource (196 pages) colour illustrations, colour maps

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