The shaping of plant axes and crowns through tropisms and elasticity: an example of morphogenetic plasticity beyond the shoot apical meristem

What is it about?

What drives the shaping of plant stems and crowns, from herbs to trees ? Crown shape is a recognizable feature of a plant; yet it is able to change drastically with changing environment, a process known as phenotypic plasticity. Indeed, plant stems and branches are shaped in response to external physical cues such as light and gravity . This is called tropism. However, they also sense their current shape through proprioception, and their position relative to their neighbours. Besides, lateral axes display an anti-gravitropic offset. Major genes such as TAC1 LAZY or WEEP have be found to control these responses, through pathways involving major plant hormones such as auxin. Linking all this into the dynamics of plant shaping requires interdisciplinary cross-talk between physics and physiology. In this review, we explain pedagogically how biophysical modelling has been used to unravel the interactions between these various sensing and the way they drive the morphogenesis of plant stems and crowns. And we show that this is giving insights on how genes control stems and crowns shapes, as well as on how this shaping can be so plastic.

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