Exploring the Limitations for Cotton Growth and Yield K. Raja Reddy Harry F. Hodges ABSTRACT. Most crops do not achieve their genetic potential, even under the best crop husbandry, because of environmental constraints. Improvements in crop adaptation to environmental stresses can be better assessed if the maximum potential is known. Here, we report the results' from cotton plants grown in naturally lit growth chambers in which tem- perature and atmospheric carbon dioxide concentration [CO2] were con- trolled and varied systematically under optimum water and nutrient c conditions. Photosynthesis of cotton canopies was measured continu- ously along with other related vegetative growth parameters and abiotic variables. Cotton canopies growing under potential growth conditions intercept most of the radiation available in the US Midsouth after begin- ning f1owering and are not light-saturated. Present-day cotton cropping practices schedule the maximum crop demand for photosynthates to oc- cur during declining solar radiation. Growing plants in high CO2 results K. Raja Reddy is Professor of Plant Physiology, and Harry F. Hodges is Emeritus Professor. Both are affiliated with Department of Plant and Soil Sciences, Box 9555, i 117 Dorman Hall, Mississippi State University, Mississippi State, MS 39762. Address correspondence to: K. Raja Reddy at the above address (E-mail: krreddy@ pss.MsState.edu). The authors thank Drs. Tom Cothren, John Hesketh, Steven Hollinger, Mike Jones, Yokov Pachasky, and Richard Vanderlip for critical review and suggestions and the contribution from the Department of Plant and Soil Sciences, Mississippi State Univer- sity, Mississippi State, MS as journal paper no. J9338. Appreciation is expressed for the excellent technical assistance provided by Gary Burrell, Kim Gourley, Wendell Ladner, and Sam Turner; and Dr. James McKinion for the SPAR facility. This research was funded by the USDOE National Institute for Global Environment Change through the South Central Regional Center at Tulane University (DOE cooper- ative agreement no. DE-FC03-90ER 61010). Journal of New Seeds, Vol. 8(2) 2006 Available online at http://jns.haworthpress.com @ 2006 by The Haworth Press, Inc. All rights reserved. doi: 10.1300/Jl 53v08n02_01 1