Abstract
The true diversity of plant species with structural colour originating in their leaf surfaces has remained unknown despite decades passing since the first relevant scientific investigations. Only five species have been found with a helicoidal cellulose basis for their colour. Of the studies that discussed the ecology of these plants, all stated that they exist in extreme shade within tropical rainforests. From so few studies, the impression given is that such plants are extremely rare and that any adaptive significance of this trait is relevant only for the few plants specialised to tolerate this specific ecological niche.Until very recently, studies of plants with structurally coloured helicoidal cellulose have investigated novel structures in specific plants. These are illuminating and form the foundations for our knowledge, but there remains a great deal more to be understood. Does the small number of species described accurately reflect the abundance of this trait? How widespread is this mode of structural colour? How many times have such iridescent leaves evolved? Is there a link to plant ecology? And is it possible to hypothesise an adaptive significance for the structures that cause the colour?
This exploratory study demonstrates that helicoidal cellulose in the adaxial leaf epidermis is considerably more common than is currently known and is found in at least 85 species within 24 genera. These genera are either ferns or angiosperms, but the distribution of these plants in the fern and angiosperm phylogenies is markedly different. Convergent evolution has been found to have taken place numerous times and the ecology of these plants far more diverse, providing insights into why these photonic crystals may have evolved in their leaf surfaces.
| Date of Award | 23 Mar 2021 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Heather M Whitney (Supervisor), Paula J Rudall (Supervisor) & Ruth Oulton (Supervisor) |
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