Date Available


Year of Publication


Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation


Agriculture, Food and Environment


Plant and Soil Sciences

First Advisor

Dr. Jan A. Smalle


Secondary metabolites are a broad class of specialized compounds that mediate plant-environment interactions and mitigate stress. It is increasingly clear that many phenylalanine-derived secondary metabolites are nearly indispensable for plant survival and that plants adjust their growth according to their secondary metabolic outputs. Consequently, many phenylalanine-derived secondary metabolites have influence over hormone activity. For instance, multiple phenylpropanoid intermediates and catecholamines alter the sensitivity of plants to the central hormone auxin, which in concert with cytokinin directs most aspects of plant growth and development. This dissertation reviews previous research on the influence of phenylpropanoid intermediates and catecholamines on plants, with a focus on their impact on auxin and cytokinin signaling. In addition, original data is presented on the impact of exogenous dopamine on auxin activity and plant physiology, illustrating that dopamine appears to affect plant growth by altering auxin transport, plant redox status and iron homeostasis. Expanding on the influence of phenylalanine-derived compounds on auxin signaling, data indicating that trans-cinnamic acid or its derivates influence auxin and cytokinin driven developmental processes. Collectively, this dissertation aims to highlight the profound impact of phenylalanine-derived secondary metabolites on plant growth and development, which presumably allows plants to simultaneously adapt their growth and metabolic outputs in response to their environment.

Digital Object Identifier (DOI)

Funding Information

This work was funded by United States Department of Agriculture / National Institute of Food and Agriculture pre-doctoral fellowship #2020-67034-31753 to T. E. Shull (2019-2022)