Date of Award:

12-2024

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Committee Chair(s)

Bruce Bugbee

Committee

Bruce Bugbee

Committee

Paul Johnson

Committee

Grant Cardon

Abstract

Cannabis sativa L. is a crop with growing medical and commercial significance. However, cannabis is not as well studied or understood as many of the most common crops. A novel area of research surrounds how much light the plant can tolerate or use to keep increasing flower yield. In agriculture, light intensity is often measured by how many light particles interact with a given area in a second, referred to as photosynthetic photon flux density (PPFD). For example, at Utah State University in Logan, Utah, during the peak of summer, the sun's light intensity can reach about 2000 μmol·m-2·s-1 at solar noon. Light intensity varies throughout the day, so scientists also use a measurement called the daily light integral (DLI), which totals all the light a plant receives over a day. In Logan, the peak DLI during summer is around 60 mol·m-2·d-1. Based on what we observed with light responses with a single leaf measurement, cannabis, as an entire plant, could thrive under even more intense light than what it typically receives from the sun. Advances in LED technology now allow us to simulate such high-light conditions in controlled environments. We explored the effects of intense light on growth, yield, height, flower shape, plant shape, cannabinoid content, and cannabinoid concentration of medical cannabis. We observed that as light intensity increased, biomass, flower yield, and cannabinoid content (g·m2) increased. With increasing light intensity, we observed a reduction in height, higher flower compactness, and density in the cultivar "Fun-dip", a decrease in CBD concentration in the cultivar "Jack", and increased resource allocation to stems in the cultivar "Jack". Cannabis breeding may change to breed for genetics that can take advantage of high light by producing larger, denser, and more marketable flowers.

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