ORCID

0009-0004-3820-1817

Keywords

photosynthesis, function-valued traits, phylogenetics, Helianthus

Abstract

Photosynthesis is a critical metabolic process in plants involving ‘light reactions’ that capture solar energy to produce ATP and NADPH, and ‘dark reactions’ where these molecules power the enzyme Rubisco to synthesize sugars in the Calvin-Benson cycle. These processes serve as the primary energy source for plant growth and reproduction, displaying significant variation across species and environments. In Helianthus, distinct differences in photosynthetic traits are observed between annual and perennial species. Notably, carboxylation rates, photon capture, and maximum photosynthetic rates show strong phylogenetic signal (Pagel’s λ = 0.99) and are significantly higher in annuals. Photosynthesis is modeled here as a multivariate function-valued trait using the non-rectangular hyperbola model, and methods to test and compare different photosynthetic models are made accessible for researchers to implement in the R package photosynthesisLRC.

Genetic diversity in chloroplast genes related to photosynthesis reveal signs of positive selection on a suite of genes involved in the light reactions, and distinct genotypes are identified between annual and perennial species. Phylogenetic generalized least squares analysis indicate selective pressures from dry, arid environments as primary drivers of evolution in photosynthetic genes. These pressures promote increased CO2 specificity and catalytic activity in Rubisco, enhance the operations of light-harvesting complexes under high light intensities, and improve molecules responsible for energy production and chloroplast repair. The photosynthetic adaptations identified here have broad implications for evolutionary ecology and could be used to inform crop sunflower breeding programs aimed at improving photosynthetic efficiency and resilience to environmental stressors.

Completion Date

2025

Semester

Spring

Committee Chair

von Kalm, Laurence

Degree

Doctor of Philosophy (Ph.D.)

College

College of Sciences

Department

Biology

Identifier

DP0029285

Document Type

Dissertation/Thesis

Campus Location

Orlando (Main) Campus

Additional Files
Supplemental Data_CH1.zip (28042 kB)
Supplemental Data- Chapter 1 FVT analysis
Table S1_NLS fits for all observations_CH1.xlsx (34 kB)
Table S1 NLS fits
Table S2-S6_CH1.docx (187 kB)
Table S2-S6
Table S7_Univariate Signal_CH1.xlsx (32 kB)
Table S7 Phylogenetic signal in univariate traits
Table S8_BEB results M8_CH3.xlsx (33 kB)
Table S8 BEB results
Table S9_PGLS_CH3.xlsx (141 kB)
Table S9 Phylogenetic ANOVA
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