HydroShoot: a functional-structural plant model for simulating hydraulic structure, gas and energy exchange dynamics

A new model is able to predict the effect of training systems on grapevine gas-exchange dynamics under drought.

Combined water deficit and heat stress due to climate change are expected to negatively affect viticulture. One short-term solution is to modify grapevine training systems (i.e. canopy architecture management) so that to maximize the ratio between net photosynthesis and water loss through transpiration whilst minimizing the risk of heat stress. With a great number of possible canopy structure designs, computer models can be used to accurately predict the influence of canopy architecture on its gas exchange rates and leaves temperature under combined water and heat stress.

A computer model of a plant

Albasha and colleagues recently published a paper in in silico Plants that presented a new model, which was able to reproduce the effect of grapevine canopy architecture on plant-scale gas-exchange processes under varying soil water conditions. The model, HydroShoot, is a leaf-scale-based functional-structural plant model (FSPM) that allows predicting whole plant transpiration and photosynthesis rates by scaling-up these processes from the leaf-level.

HydroShoot is the first grapevine FSMP to account for the interactions between water status, energy budget and gas-exchange rates at the leaf scale. These are represented as three interacting modules:

  • hydraulic which calculates the distribution of xylem water potential across shoot hydraulic segments (i.e. shoot hydraulic structure),
  • energy, which calculates the complete energy budget of individual leaves, and
  • exchange which calculates net carbon assimilation and transpiration rates of individual leaves.

“Our team coded HydroShoot to complete earlier work on grapevine FSPM where simulations could only be run under well-watered conditions. We assumed that successfully accounting for drought conditions in an FSPM requires simulating both the hydraulic structure of the shoot together with the energy budget of individual leaves.” says Rami Albasha, Crop modeler at the Intelligence Technology Knowledge (itk) society, former postdoctorate in plant ecophysiology at the French National Institute for Agricultural Research (INRA).

Grapes on a vine
Frontenac grapes on the vine, Flying Otter Vineyard and Winery. Image: Dwight Burdette / Wikipedia

The authors found that although both hydraulic structure and energy balance simulations were required to reproduce accurately plant-scale gas-exchange rates under soil water deficit, yet, the hydraulic structure had, by far, the largest effect on the simulated rates, at least for the grapevines considered in this study.

HydroShoot is available through the OpenAlea platform (https://github.com/openalea/hydroshoot) as a set of reusable modules.