# Can we estimate tree hydric status thanks to a transportable MRI sensor?

Guilhem Pagés, Shannan Blystone, Jean-Marie Bonny, Hervé Cochard

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Guilhem Pagés, Shannan Blystone, Jean-Marie Bonny, Hervé Cochard. Can we estimate tree hydric status thanks to a transportable MRI sensor?. GERM 2025, Jun 2025, Autrans (Grenoble), France. hal-05119044

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Submitted on 18 Jun 2025

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# Can we estimate tree hydric status thanks to a transportable MRI sensor?

Guilhem Pagés, Shannan Blystone, Jean-Marie Bonny, Hervé Cochard

Grasslands and forests play a crucial role in mitigating global warming due to their significant capacity to store carbon. Water is essential in this process, as it acts as a reactant in converting carbon dioxide into sugars during photosynthesis. In the context of global warming and climate change, understanding how plants manage water is critical. However, there is currently no sensor capable of locally probing water content and its movement directly in plants within their natural environment—i.e., *in situ*.

Magnetic resonance imaging (MRI) is the preferred analytical tool for non-invasive, localized measurement of water properties. To make these instruments transportable, low-magnetic-field devices have been developed,¹ including unilateral magnets.² With such unilateral instruments, like the NMR-MOUSE,³ the sample is placed at the magnet's surface, and the signal is recorded in a thin slice at a known distance from the surface. By precisely adjusting the magnet's position using a high-precision lift, a 1D image or profile can be obtained.

Few portable devices have been used to study plant function in situ.⁴ We have customized an NMR-MOUSE to readily perform measurements outside the laboratory and demonstrated that the measurements were quantitative. To go further, we evaluated the sensor sensitivity by performing drought experiments on pine trees in pots. We demonstrated that the information obtained thanks to the transportable MRI sensor were complementary to the ones obtained from classical ecophysiological sensors. The vulnerability curve, which reports on the tree hydric status by linking the xylem pressure to a mortality probability, is a value highly used by plant physiologists. We compared the classical vulnerability curve for our pine trees with a similar plot obtained by our transportable MRI sensor. One main hypothesis was raised to explain the differences observed between both methods.

## REF

1. Nagata, A.; Kose, K.; Terada, Y. *J. Magn. Reson.* 2016, **265**, 129-138.
Meixner, M.; Kochs, J.; Foerst, P.; Windt, C. *J. Magn. Reson.* 2021, **323**, 106879.

2. Blümich, B.; Blümler, P.; Eidmann, G.; Guthausen, A.; Haken, R.; Schmitz, U.; Saito, K.; Zimmer, G. *Magn. Reson. Imag.* 1998, **16**, 479-484.

3. Rehorn, C.; Blümich, B. *Angew. Chem. Int. Ed.* 2018, **57**, 7304-7312.

4. Blystone, S.; Nuixe, M.; Traoré, A.; Cochard, H.; Picon-Cochard, C.; Pagés, G. *Plant Meth.* 2024, **20**, 31.

## IMAGE

<figure><img src="image_2.png" /><figcaption>**Figure:** (Left) Illustration of in situ experiments using our transportable MRI and (right) comparison of the vulnerability curve obtained by using the classical approach (grey) and the MRI sensor (colored dots). The vulnerability curve links the xylem pressure to a mortality probability, e.g., at a xylem pressure around -5 MPa, 50% of the pine trees are dead.</figcaption></figure>