Hydraulic connections: Modeling shoots hydraulic architecture of grapevine to apprehend leaf-scale gas exchanges and WUE in complex canopies
Résumé
Although grapevine (Vitis vinifera) is reputed for its high adaptability to low water availability
conditions, global warming and the resulting aleatory water deficit events has raised concerns in
developing new training systems adapted to the changing climate context (Medrano et al., 2012).
Such training systems are thus called to optimize water use while preserving the production
quantity and quality.
In this study, the Functional-Structural Plant Models (FSPM) approach was used to estimate the
grapevine gas exchange dynamics resulting from different training systems under water deficit
conditions. The cornerstone of this work is the simulation of the stomatal conductance gs at the
leaf scale as a function of both the local micro-climate conditions and the plant/soil water status.
gs is simulated as a function of the net assimilation rate (An), vapor pressure deficit (VPD) and
inter-cellular CO2 concentration (Ci) as described by Leuning (1990). The soil/plant water status
effect on gs is accounted for by relating gs to the leaf water potential ΨL according to the empirical
approach (Damour et al., 2010). ΨL is related to the collar water potential ΨC (which represents
the averaged soil water potential in the root zone) using three methods of different degrees of
complexity: (1) ΨL is considered uniform among all the leaves and is equal to ΨC (assuming thus
that the stem conductance in negligible); (2) ΨL is function of ΨC and varies locally with the
transpiration flux density (E) but no hydraulic connection is considered between the leaves; (3) ΨL
is function of ΨC and E with leaves being hydraulically connected using a complete description of
the shoot hydraulic structure of the plant.
The results of this study aims at providing answers to leaf-scale physiological responses of
grapevine under water deficit conditions for different canopy structures. The resulting model
could be used to assist training systems design to optimize water use efficiency.
Format : Poster