Submitted to: Advances in Modeling Agricultural Systems
Publication Type: Book / Chapter
Publication Acceptance Date: 11/15/2007
Publication Date: 2/1/2009
Citation: Timlin, D.J., Yang, Y., Kim, S., Bunce, J.A., Anapalli, S., Fleisher, D.H., Quebedeaux, B., Reddy, V. 2009. Simulation of the effects of limited water on photosynthesis and transpiration in field crops: Can we advance our modeling approaches? In: Ahuja, L.R., Reddy, V.R., Saseendran, S.A., & Yu, Qiang, editors. Response of Crops to Limited Water: Understanding and Modeling Water Stress Effects on Plant Growth Processes: Vol. 1. Advances in Modeling Agricultural Systems. Madison, WI. American Society of Agronomy. p.105-143. Interpretive Summary: Scientists build computer simulation models of agricultural crops in order to predict how a crop will respond to management practices and weather. These problem solving tools are well-suited to addressing many challenges facing agriculture today. Many of the current models however, are still not accurate enough to respond to drought realistically. This research describes and compares several new approaches to predict the effect of drought on plant growth. These new approaches have been successfully incorporated into a new simulation model for corn developed by the ARS. This research will result in more robust crop models that can be used as assessment tools in agriculture.
Technical Abstract: The biggest challenge to simulation models of agricultural crops is the accurate quantification of the physiological responses of crop growth and development to non-optimal changes in its physical and chemical environment. A large body of research has addressed knowledge gaps in our understanding of how plants react to environmental stress. Much of the results from this research, however, have been qualitative and difficult to translate into quantitative relationships. As a result, plant response to environmental stress is often modeled using empirical relationships based on macroscopic observed behavior. The purpose of this review is to provide an 1) overview of how water impacts processes that are important from the perspective of simulation modeling of stomatal control and gas exchange, 2) summarize recent research in this area of plant response to water stress, and 3) show how these advances can be used to improve our abstractions of plant growth and development under non-optimal water availability. We review several new approaches to modeling stomatal conductance and photosynthesis using coupled models of stomatal control and gas assimilation. Models of stomatal control use some measure of vapor pressure deficit and carbon assimilation rate. Although they are more mechanistic than previous models, they are still based on correlative relationships. When coupled with models of photosynthesis, they do provide realistic simulations of carbon assimilation and transpiration over a range of water availability but still have a high level of empiricism. Other approaches to model of stomatal control accounting for effects of plant hormones, hydraulic conductance and guard cell dynamics are also promising. Use of these methods can improve crop models for prediction of transpiration and photosynthesis under water stress.