The Interactions Between Circadian Rhythms and Herbicides

Abstract

Global food production is required to increase by more than 70% by 2050 in order to feed the growing population, since global population is expected to increase by more than 2 billion. A major constraint on crop yield is weeds; within the field, weeds compete with crops for resources such as light, space, and nutrients. Herbicides are used to control weeds; however, herbicide overuse has led to increased resistance of plants in addition to environmental pollution. Furthermore, over $11 billion is spent per year on herbicides in the USA alone. As such, it would be beneficial to use herbicides more effectively.

Plants, as sessile organisms, possess a circadian oscillator that is responsible for adapting the timing of processes within the plant to the changing environment, in order to enhance fitness. The circadian oscillator can also restrict responses to stimuli to specific times of day, which is known as circadian gating. Herbicides have previously been observed to have fluctuating efficacy dependent on the time of application. Therefore, it was hypothesised that the circadian oscillator might restrict certain responses to herbicides to specific times of day. The interactions between herbicides and the circadian oscillator were investigated in depth in this thesis.

Three different mode-of-action herbicides were investigated: glyphosate, mesotrione and terbuthylazine. This thesis presents data relating to two overarching findings. (i) The circadian oscillator can regulate signalling or metabolism to produce varying levels of efficacy depending on the time of herbicide application. (ii) Herbicides can alter the emergent properties of the circadian oscillator, potentially causing dissonance between the plant and its environment.

These results led to the proposal of a new concept that we have termed agricultural chronotherapy. In a wider context, this could improve the use of agrochemicals in the future.

Date of Award	28 Nov 2019
Original language	English
Awarding Institution	University of Bristol
Supervisor	Keara A Franklin (Supervisor) & Antony Dodd (Supervisor)