ROOTSTOCK - Plant root development affected by soil mechanical stresses

ROOTSTOCK
- Plant root development affected by soil mechanical stresses

20/08/2026 Financement de l'Union européenne

ROOTSTOCK
- Plant root development affected by soil mechanical stresses

Biomechanics, plant roots, C storage, mechanical stresses, morphogenesis

PRISM programme

The PRISM (PhD Research Programme for International Training in Sustainable Soft Matter) programme has launched its first call for applications, offering up to 14 fully funded PhD fellowships starting from 1 March 2027 at Paris Sciences & Lettres (PSL) University. The programme trains researchers to address ecological transition challenges through sustainable soft matter science, with projects focused on eco-friendly chemical processes, circular economy, renewable energies, and carbon capture, storage, and valorisation. Co-funded by the European Union under Horizon Europe MSCA COFUND (Grant Agreement 101261637) and partner institutions, PRISM provides interdisciplinary, international, and intersectoral training, including mobility opportunities, secondments, and courses in sustainability, innovation, entrepreneurship, career development, and transferable skills.

Applications must be submitted only via the PRISM website (https://prism.psl.eu/en/) between 1st September to31 October 2026 (23:59 Paris time).

The PhD project

In the context of climate change mitigation, the ‘4 per 1000 Soils for Food Security and Climate’ initiative launched during the COP21 states that an increase in global soil organic matter stocks in agricultural soils by +0.4% per year could offset 20-35% of anthropogenic greenhouse gas emissions. Thanks to photosynthesis, plants are one of the most efficient system to transfer C from atmosphere to soils and to capture C through biomass increase via the development of plant roots. However reliable estimations of root C inputs to soil are currently lacking, partly because of the difficulty in quantifying and predicting the root system extent in opaque and heterogeneous soils. Responsiveness to change in environmental cues, called developmental plasticity, is markedly large for roots. Root system development is highly modulated by biological (competition and symbiosis with other organisms), chemical (nutrient availability, oxygen supply, pH…) and physical properties of soils. The architecture of the root system, that is its three-dimensional shape, largely derives from the distribution and diversity of individual root apical meristems, which continuously sense and adjust their growth according to their local environment. In particular, root growth is affected by the mechanical strength of the soil and by the presence of obstacles which scale match or exceed that of the root. As a consequence, the presence of zones of high mechanical resistance in the soil is one of the most common physical limitations to soil exploration by roots, with direct consequences on the C sequestration but also on the agricultural yield. In contrast to aerial organs, roots apices must exert a growth pressure to penetrate strong soils and reorient their trajectory to cope with obstacles like stones or to follow the tortuous paths of the soil porosity. When the soil becomes too compact due for instance to droughts, the mechanical strength of the soil increases and the distribution of poral network changes, resulting in growth arrest.

In this interdisciplinary context, we have developed at PMMH experimental model systems to study the biophysical mechanisms underlying root responses to obstacles. The model systems include single or a collection of obstacles mimicking the mechanical heterogeneities in a soil. In particular, we investigate the growth response of a root pushing against a single obstacle such as a force sensor or growing inside a 3D-printed array of stiff obstacles. By coupling force and growth kinematics measurements under infra-red lighting, we probed the force-growth relationship of a primary root contacting a stiff resisting obstacle.

The PhD-project aims at identifying the biophysical laws governing the spatial extent of a root system in an heterogeneous soil. A first approach is to investigate the response of the root to prescribed compression steps with controlled force to study its time-dependent mechanical properties and to decouple the mechanical responses from the biological feedbacks. Another approach is to use microfluidic systems to build arrays of granular substrates of soft hydrogel to vary the stiffness of obstacles encountered by roots as well as controllig the osmolarity of the external medium.

INTERNATIONAL: The current project follows a previous PhD project on the effect of the structure of granular media on root growth (Jiaojiao YAO, 2025). It was conducted as part