John S Choinski, Jr.
Professor of Biology
Department of Biology
University of Central Arkansas
Conway, AR 72035
Telephone: (501) 450-5918
Fax: (501) 450-5914
Email: email@example.com or firstname.lastname@example.org
Principles of Biology II (Biology 1441)
Economic Botany (Biology 3390)
Plant Ecophysiology (Biology 4450/5450)
Organisms in Extreme Environments (Biology 4490/5490)
I am a plant physiologist interested in how photosynthesis rates change during leaf expansion. My students and I have discovered that young, immature leaves have higher midday temperatures than more mature leaves because of limited transpirational cooling capacity. Additionally, young leaves are more photosynthetically thermotolerant than mature leaves possibly because of differences in chloroplastic membrane fatty acid saturation levels. Although I have worked with many different species of trees, recently we have been focusing on the important crop plant, cotton. The image below is of 50-day-old field grown Gossypium hirsutum (Upland Cotton) showing leaves in various stages of expansion. In bright sun, the smallest leaves are sometimes 10¡C or more warmer with photosynthetic thermal optima 10-15¡C higher than larger, more mature leaves. Understanding the mechanisms behind changes in temperature tolerance in expanding leaves will be an important part of learning how cotton and other plants adapt to predicted rises in global temperature, increasing desertification and other environmental changes.