Date of Award:

8-2021

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Plants, Soils, and Climate

Committee Chair(s)

Bruce Bugbee

Committee

Bruce Bugbee

Committee

Lawrence Hipps

Committee

Marc van Iersel

Committee

Lance Seefeldt

Committee

Raymond Wheeler

Abstract

Photons are the primary energy source for most life on Earth, as they drive photosynthesis, a process that turns the CO2 in air into food. One crucial parameters for the optimization of growth is leaf area, which determines the ability of a plant to capture photons for photosynthesis. In order to gain access to photons in shaded environments, plants have evolved unique sensors, called photoreceptors, which respond to changes in the color and intensity of light.

Far-red photons (photons at the edge of human vision that appear as dim red light) hold particular promise in regulating plant shape and photon capture. These photons are minimally absorbed by chlorophyll, and are thus enriched in the shade – making them a potent signal of the presence of shade. These photons have been shown to increase leaf area and stem elongation, which increase access to photons, and thus increase plant growth. Additionally, the lower energy of far-red photons make them particularly useful for reducing the massive requirement for electrical power in indoor agriculture.

Here, I describes how far-red interacts with blue, green, and red photons to affect plant morphology. I compare traditional and newly developed models/metrics that predict the action of far-red through a photoreceptor called phytochrome. Additionally, I discuss their interactions with total photon intensity.

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