Investigating Synthetically and Naturally Augmented Photosynthesis in Chlamydomonas reinhardtii, Begonia and Selaginella

Abstract

Photosynthesis is fundamental to the survival of all life on Earth. Light harvesting and photoregulation are critical elements of the intricate processes and are key determinants of growth and survival of photosynthetic organisms. Both natural and synthetic nanostructures have been shown to augment these processes, however, the precise mechanisms by which this occurs are not fully understood. Two different systems were investigated to further probe this. The first system was chosen to explore if functionalised nanoparticles could augment photosynthetic function and enhance growth rates. The second probed photosynthesis which is enhanced by naturally occurring photonic effects in the chloroplasts of understory species.

The effect of carbonaceous nanoparticles, carbon dots (CDs), on the growth of microalgae Chlamydomonas reinhardtii were investigated with an array of techniques. The CDs were shown to have switchable effects on growth depending on surface functionalisation; unfunctionalised CDs led to cell death and complete growth inhibition, while glucose/biomolecule functionalised CDs significantly increased cell density by (~170%). The induced toxicity was determined to be a result of photoinduced ROS production from CDs, while the precise mechanism of enhancement was unclear, changes in non-photochemical quenching induction and relaxation were induced by CD treatment.

Some species of Begonia and Selaginella have highly ordered ultrastructures in their upper epidermal chloroplasts, termed iridoplasts and bizonoplasts. The nanoscale ordering of these photosynthetic structures has been previously demonstrated that they possess photonic properties. Time-resolved fluorescence lifetime measurements of individual chloroplasts and iridoplasts within five different species were investigated. The chlorophyll fluorescence lifetimes of the iridoplast/ordered regions of bizonoplasts were shown to be significantly shorter than their typically disordered counterparts. These differences potentially occur due to the Purcell effect within the chloroplasts, and if so, are to the best of our knowledge the first report of this phenomenon in a living organism.

Date of Award	18 Jun 2024
Original language	English
Awarding Institution	University of Bristol
Supervisor	Tom Oliver (Supervisor) & Heather M Whitney (Supervisor)