Stick or twist? Decision-making and risk-aversion in plant development

Plants continually integrate environmental information into their developmental program, in order to achieve optimal shoot and root systems for prevailing conditions. Ultimately, this allows them to maximise their reproductive success in the face of an unpredictable climate. The process by which plants elaborate these optimal architectures can be characterised as 'decision-making', because it involves careful balancing of priorities, trade-offs and bet-hedging. These decisions are not simply a response to the environment, since these decisions are made in the absence of resource limitations. Rather, decision-making processes are geared around avoiding future resource limitations, and as such, plant development is characterised by a high degree of risk-aversion. In this seminar, I will discuss two key examples of decision-making in plants, and describe the regulatory mechanisms that permit plants to make complex calculations about their development. Firstly, I will focus on the phenomenon of root-to-shoot signalling, and how plants integrate information about their soil environment to make decisions about the size of their shoot system. Secondly, I will discuss reproductive development, and how plants decide how many flowers, fruits and seeds to make, and how to arrange them in time and space. A small number of hormonal signals, including auxin, strigolactones and cytokinins, seem to act the key informational conduits in both these decision-making systems. I will discuss how these hormonal systems allow individual organs to perceive the global resource and developmental status of the plant, and to make devolved local decisions which are nevertheless coherent across the plant.

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