Open Collections

Garen, Josef

University of British Columbia

Photosynthesis drives energetic processes in the biosphere and is the single largest terrestrial flux in the global carbon cycle. Climate change has already increased global mean temperatures by 1.1 °C above the preindustrial average, with substantial additional warming forecast under most climate change scenarios. Understanding and forecasting the effects of climate change on vegetation is therefore a task of extreme urgency, as photosynthesis plays a central role in climate mitigation strategies and provision of food and natural resources. In this dissertation, I endeavour to improve our understanding of plant photosynthetic temperature response through four studies. In Chapter 2, I derive and test predictions from an extended metabolic scaling model, showing that thermal acclimation of photosynthesis plays a central mediating role in structuring growth rate temperature response. In Chapter 3, I develop an improved method for measuring the acute temperature response of leaf-level photosynthesis. This method decreases measurement time by a factor of approximately 3.3 and increases data density by a factor of approximately 55 compared to conventional methods, while accurately reproducing temperature response parameter estimates. In Chapter 4, I employ the method developed in Chapter 3 to collect a large assimilation-temperature response dataset representing a wide range of phylogenetic and functional diversity in temperate-climate vascular plants. Using this dataset, I find that local environmental conditions are much stronger predictors of plant assimilation-temperature response than climate of origin, functional traits, or phylogeny. In Chapter 5, I investigate pathways of water loss in plant leaves. By partitioning leaf minimum conductance into stomatal and cuticular components at a range of temperatures, I find that the dominant pathway of water loss in leaves shifts increasingly toward cuticular transpiration with increasing temperature. Further, I show that cuticular conductance has large, temperature-dependent effects on estimates of photosynthetic capacity, particularly in species with low rates of stomatal conductance.

Text

2024-07-11

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/88623

Botany

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/