Public Thesis Defense - ELI

Quantifying soil-grapevine hydraulics from plant to field scale by Louis DELVAL

Pour l'obtention du grade académique de Doctorat en Sciences agronomiques et Ingénierie biologique

Grapevine (Vitis vinifera) is the world’s third most valuable horticultural crop. Today, climate change significantly threatens grape productivity, notably due to more frequent and extended drought periods. To address the critical issue of grapevine response to water stress, soil-plant hydraulic processes can be considered the cornerstone of the physiological mechanisms involved in grapevine tolerance to drought. Although recognized, the key role of belowground hydraulics on grapevine water status is rarely addressed because difficult to measure. This PhD thesis aims to understand how soil-grapevine hydraulics impacts the transpiration rate, water potential and root water uptake of in situ grapevine cv. Chardonnay. At the plant scale, we first revealed experimentally that the transpiration control of grapevine is soil texture specific and is triggered by a decrease of belowground hydraulic conductance, rather than xylem cavitation in the stem. We also highlighted the coordination of short-term hydraulic responses with longer-term growth strategies. Then, by using a biophysical model representing explicitly the series of hydraulic conductances between the bulk soil and the stem, we demonstrated that, during drought, root water uptake is mainly limited by the rhizosphere in coarse-textured soil, while it is the root system that controls root water uptake in fine-textured soil. Finally, a field scale experiment, in non-irrigated vineyards, provided evidence that the spatial distribution of grapevine leaf water potential is mainly governed by the within-vineyard soil hydraulic conductivity heterogeneity, especially during drought. By quantifying soil-grapevine water relations in different edaphic conditions during drought, this PhD thesis provides insights that could help winemakers to ensure better adaptation to climate change and enhance vineyard resilience.

Jury members :

• Prof. Mathieu Javaux (UCLouvain) (Supervisor)
• Prof. François Jonard (UCLouvain) (Supervisor)
• Prof. Marnik Vanclooster (UCLouvain) (Chairperson)
• Prof. Bruno Delvaux (UCLouvain)
• Prof. Xavier Draye (UCLouvain)
• Prof. Cornelis Van Leeuwen (Bordeaux Sciences Agro, Fr.)
• Prof. Jan Vanderborght (Forschungszentrum Jülich, Germ.)

Pay attention : the public defense of Louis DELVAL will also take place in the form of a videoconference

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