| Summary: | Background: Auxin, a plant hormone, has been shown to be integrally linked to plant growth. However, due to the small size of auxin molecules it is experimentally difficult to estimate the concentration of auxin within a cell. Therefore, mathematical modelling is a useful tool in testing predictions and understanding auxins behaviour. Two important systems relating to auxin are: auxin transport, the way auxin moves through plant tissue and the patterns it forms; and auxin signalling, the pathway through which auxin affects the activation and repression of genes through auxin sensitive proteins. However, the exact dynamics of auxin transport and auxin signalling remain unclear.
Aims: The aim of this thesis is to explore experimentally observed interactions relating to auxin signalling and transport in a modelling environment. This is in the pursuit of understanding their potential ramifications and interactions. Therefore, to address this aim we studie several pre-existing auxin transport and signalling models, altering them to introduce related phenomena and examining how they react.
Chapters (3-5): In Chapter 3 we examine the effects that cell growth and elongation has on concentration-based auxin transport models. In Chapter 4 we investigate how oscillations in auxin concentration affect auxin signalling models to study how oscillatory behaviour in an auxin transport model might affect auxin signalling. Finally, in Chapter 5 we explore auxin signalling in the ancestral plant Marchantia polymorpha, testing whether our current understanding of its auxin signalling system is sufficient to explain some experimentally observed behaviour.
Conclusions: Findings show that the introduction of growth may induce oscillations in auxin concentration within a concentration-based auxin transport model. We also go on to show that oscillations in auxin concentration, like the aforementioned ones, can alter the period of oscillations in an auxin signalling system and exhibit behaviour similar to resonance. Finally, we show that a mechanistic auxin signalling model for Marchantia is currently unable to produce the expected results at this time.
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