Biomechanics and architecture of developing plant organs

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Plants are constantly challenged mechanically, by wind, heavy snow falls or even their own weight. In wood, mechanical resistance comes from lignified remains of dead cells. In contrast, shoots and roots need to keep their cells alive and grow quickly in search of light or nutrients. Young plant organs have therefore to use smart mechanical strategies to stay straight, e.g. when pushing through hard soil during germination, while remaining flexible and dynamic. Some of the genes essential for organ growth and posture have been identified, but genes can only act via controlling biochemistry at the cellular level. We still don't know how organ behavior emerges from the interactions between individual plant cells. In this project I propose to fill the gap between gene expression and organ mechanics by combining engineering and biological viewpoints on young plant organs. Root and stem tissues are highly organized into layers of different cell size and shape, reminding of composite materials. This leads to the idea that the structure and arrangement of cells and tissue layers, i.e. organ anatomy, could have been naturally selected to optimize key biological functions such as root growth or the ability of stems to respond to mechanical loads. I propose a multi-disciplinary approach to explore the mechanical strategies used by plants to grow fast while maintaining their strength and ability to sense external forces. Combining biological experiments and modelling, I will dissect the different levels of organization of plant organs during growth. My group will develop new methods to quantify mechanical properties at different scales, from single cells to tissues and organs. Using advanced microscopy techniques, we will investigate how external forces applied at the organ level are translated at the levels of tissues and cells. Experimental data at the single cell and tissue level will be then integrated into a physically-based 3D simulations of growing plant organs. Such computational models will help us understand which factors, from cell elasticity to anatomical features, control mechanical performance and growth of the whole organ. Beyond developmental research, this knowledge can provide keys to address agricultural issues - such as crop lodging and germination in compact soils - and contribute to developing new breeding practices for a changing climate.