Degree
Doctor of Philosophy (PhD)
Department
Biological Sciences
Document Type
Dissertation
Abstract
Photosynthetic organisms convert sunlight into chemical energy while the light they receive fluctuates unpredictably over timescales from seconds to days. The photosynthetic electron transport chain carries out this conversion and is protected by overlapping regulatory mechanisms. How these mechanisms respond to the predictability of light rather than its average intensity has remained unclear. This dissertation treats photosynthetic regulation as a feedback control system and asks how that predictability shapes photosynthetic performance. Chapter 1 develops a control-theoretic framework in which four regulatory layers act on the electron transport chain. These are non-photochemical quenching as proportional control, cyclic electron flow as integral control, the flavodiiron proteins as a fast valve, and state transitions as a gain scheduler. The framework predicts that the loss of each layer should produce a distinct failure under a distinct light statistic. Chapter 2 tests these predictions in Chlamydomonas reinhardtii. Mutants lacking each control layer were examined under diurnal and total-variation-matched fluctuating-light regimes. The predictability of light sets a reversible limit on photosynthetic capacity. The daily light dose does not. Genotype-specific signatures map onto distinct control layers. Loss of the flavodiiron valve remodels photosystem stoichiometry. Loss of state transitions unmasks a response of non- photochemical quenching to predictability that is otherwise suppressed. Chapter 3 turns to the donor side of Photosystem II and the dynamics of water oxidation. The empirical wavelet transform decomposes a flash-oxygen sequence into the period-four oscillation of the oxygen-evolving complex and the overlapping period-two oscillation of the acceptor side. The separation improves recovery of the catalytic S-state parameters and is validated on simulated, newly measured, and archival datasets. These chapters together establish the temporal predictability of light as an independent axis of the light environment. They also show that the time-resolved dynamics of photosynthetic regulation and catalysis can be dissected with tools drawn from control theory and signal processing.
Date
7-15-2026
Recommended Citation
Ferrari, Nicholas, "Dynamics and Acclimation of the Photosynthetic Electron Transport Chain in Stochastic Environments" (2026). LSU Doctoral Dissertations. 7138.
https://repository.lsu.edu/gradschool_dissertations/7138
Committee Chair
Vinyard, David J.
LSU Acknowledgement
1
LSU Accessibility Acknowledgment
1