PLANT MODELING: ADVANCES AND GAPS IN OUR CAPABILITY TO PROJECT FUTURE CROP GROWTH AND YIELD

Authors: BOOTE, K. - UNIVERSITY OF FLORIDA; PICKERING, N. - UNIVERSITY OF FLORIDA; Allen Jr, Leon

Submitted to: American Society of Agronomy Special Publication
Publication Type: Book / Chapter
Publication Acceptance Date: 10/2/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Global atmospheric carbon dioxide (CO2) is increasing. These increases are expected to cause climate changes that may affect crop productivity. In addition to experimental information, we need improved crop computer simulation models to more accurately predict the effects of rising CO2 and future climate changes on yields. In recent years, we have improved our understanding of the way that CO2 concentration drives leaf photosynthesis. Scientists in the Crop Genetic and Environmental Research Unit in Gainesville, FL have incorporated this knowledge into a few crop models. Also, the effects of CO2 on leaf temperature and transpiration rates have now been included in some crop models. Two important gaps in our knowledge need to be resolved. The first is the need for a better explanation of crop species differences in acclimation of photosynthesis to elevated CO2. The second is the need for a better mechanism for coupling the photosynthesis supply to the plant growth requirements under elevated CO2 and changed climate conditions. Although crop responses to climate change scenarios have been predicted with simple plant growth models in the past, these assessments can now be performed more reliably with new, improved models.

Technical Abstract: Rising carbon dioxide (CO2) and climate changes can alter crop yields. Crop simulation models can predict physiological and yield responses to climate for various species. Much has been learned about CO2 effects on rubisco kinetics, stomatal function, photosynthesis, and leaf feedback mechanisms during the past 15 years. However, few crop models use leaf rubisco kinetics to simulate photosynthetic sensitivity to CO2 or an energy balance to predict foliage temperature and CO2-induced decreases in transpiration. We have incorporated these two advances into a canopy model that provides direct sensitivity of photosynthesis and transpiration to CO2, temperature, and humidity. Species differences in photosynthetic acclimation to elevated CO2 via regulation of the amount and activity of rubisco represent significant knowledge gaps. We need better information on CO2-enrichment effects on partitioning and source:sink imbalances for simulating feedback inhibition effects on photosynthesis. Although crop responses to climate change scenarios have been assessed with simple models, these analyses can now be performed with more mechanistic models.