Heat Stress Effects on Cotton During Reproductive Development and Subsequent Acclimation Responses

High temperature stress is among the most difficult to control abiotic factors affecting crop yields in the Southern United States due to its wide regional influence. Cotton (Gossypium hirsutum L.) though a tropical plant in origin, it is sensitive to the effects of high temperature. This is of particular concern when the warmest temperatures coincide with the most sensitive developmental stage of flowering. Thus, the capacity to improve cotton’s ability to tolerate heat stress has been a significant focus for many decades. Therefore, this research was composed of several different components all designed to investigate heat stress effects. Using a combination of environmental growth chamber, field, and exploratory data modeling studies it appears that high temperatures affect cotton fruit production ubiquitously. This conclusion, based upon the results of several novel experiments of identifying heat stress effects were summarized under the following objectives: 1) Identify historic regional effects of high temperature for both irrigated and nonirrigated fields in the Mississippi Delta 2) Determine the impact heat has on the carbohydrate status of the flower and subtending leaf the days surrounding anthesis 3) Characterize acclimation potential to repeated periods of heat stress that emphasizes that the timing of analytical collections is an important underreported factor in plant development 4) Investigate well-irrigated cotton and its response to heat stress to ascertain if irrigation could provide protection from increased temperatures Acknowledgements The author would like to extend his deepest gratitude towards all who provided support and guidance for this massive undertaking. I would like to first thank Dr. Derrick M. Oosterhuis, my graduate professor, who was willing to take a chance on a student whom had near zero agricultural experience. His guidance and criticism has kept me in line as I explored new techniques and methods to extract the correct results. He has been a teacher, a moderator, and more importantly a friend who has continually pushed me to do more. I appreciate the efforts of my committee members, Dr. Fred M. Bourland, Dr. Bobbie L. McMichael, Dr. Richard J. Norman, and Dr. Curt R. Rom. They have been a quiet support team who have on occasion been a valuable resource in helping me complete this degree. I greatly appreciate the work of Johnathan R. Clark. He has been invaluable as a lab assistant, but most importantly as a friend. This project would not have been possible without his assistance in the field and countless hours helping with the environmental chamber experiments. Additionally, all the former graduate students who have come through the program with me, who taught me so much about foreign culture. Each in some way challenged me to become a better person now than when I started. The experience gleaned from assisting each of your experiments has had a positive impact on this manuscript; it is as much yours as it is mine. Finally, I would like to thank my family who have consistently pushed me to succeed even under the most challenging times during my career here. It has been a journey, and I am thankful that you came along for the ride.