Coupled gas-exchange model for C4 L=leaves: Comparing stomatal conductance models

Authors: YUN, KYUNGDAHM - University Of Washington; Timlin, Dennis; KIM, SOO-HYUNG - University Of Washington

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/4/2020
Publication Date: 10/20/2020
Citation: Yun, K., Timlin, D.J., Kim, S. 2020. Coupled gas-exchange model for C4 L=leaves: Comparing stomatal conductance models. Plants. 9/1358-1386. https://doi.org/10.3390/plants9101358.
DOI: https://doi.org/10.3390/plants9101358

Interpretive Summary: Plant simulation models are abstractions of plant physiological processes that are useful for investigating the responses of plants to changes in their environment and physical structure. Photosynthesis is a basic plant process that drives growth and biomass accumulation and a basic requirement for any plant simulation model. We developed an improved computer simulation model of coupled photosynthesis and water evaporation from plant leaves as a combination of two existing approaches. We tested the model and found that the model behavior is reasonably sensitive and reliable in a wide range of environmental conditions. The new model showed improved predictions at low values of relative humidity. The coupled model, however, underestimated evaporation from leaves in very high temperatures. This limitation will be addressed in future research. This study is useful to scientists who investigate and model plant photosynthesis, greenhouse managers, ecologusts and plant breeders.

Technical Abstract: Plant simulation models are abstractions of plant physiological processes that are useful for investigating the responses of plants to changes in their environment and physical structure. Photosynthesis is a basic plant process that drives growth and biomass accumulation and a basic requirement for any plant simulation model. Here, we present a coupled gas-exchange model for C4 leaves incorporating two widely used stomatal conductance submodels: Ball -Berry and Medlyn models. The output variables of the model includes steady-state values of CO2 assimilation rate, transpiration rate, stomatal conductance, leaf temperature, internal CO2 concentrations, and other leaf gas-exchange attributes in response to light, temperature, CO2, humidity, leaf nitrogen, and soil water availability. We test the model behavior and sensitivity, and discuss its applications and limitations. The model was implemented in Julia programming language using a novel modeling framework. Our testing and analyses indicate that the model behavior is reasonably sensitive and reliable in a wide range of environmental conditions. The behavior of the two model variants differing in stomatal conductance submodels deviated substantially from each other especially in low humidity conditions. The model was capable of replicating the behavior of transgenic C4 leaves found in the literature in moderate temperatures. The coupled model, however, underestimated stomatal conductance in very high temperatures. This is likely an inherent limitation of the coupling approaches using Ball -Berry type models in which photosynthesis and stomatal conductance are recursively linked as an input of the other.