Abstract
Blue leaf iridescence has been observed in several plant species growing under the canopy of rainforests. In Phyllagathis rotundifolia, this iridescence was thought to originate from epidermal organelles termed iridoplasts. This thesis aimed to determine if the iridoplasts are the source of the iridescence, and to explore the photoprotective capabilities of these organelles.I built an epi-illumination reflectance microscope to characterise the iridescence by measuring the reflectance spectra of individual iridoplasts in vivo, as well as study the time- dependent changes in reflectance by using different light conditions, spectral and intensity, aiming to identify what triggered the changes of reflectance. Through electron microscopy (EM), I characterised the microstructure of the iridoplasts before and after light irradiation of the leaf, and correlated them with the observed changes in reflectance.
I constructed two kinds of time-correlated single photon counting (TCSPC) experiments: bulk and spatially resolved. With these instruments, I studied the fluorescence lifetimes of whole leaves and individual iridoplasts and chloroplasts of P. rotundifolia. From the bulk experiments I concluded a very fast photoprotective response of these leaves when exposed to high light, in addition to showing a higher recovery of the fluorescence when compared to other species. With spatially resolved TCSPC, the iridoplasts were observed to have a shorter fluorescence lifetime than chloroplasts. These observations could imply that iridoplasts are better adapted to react to sudden changes in light environments.
| Date of Award | 27 Sept 2022 |
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| Original language | English |
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| Supervisor | Tom Oliver (Supervisor) & Heather M Whitney (Supervisor) |