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: john.choinski@gmail.com or johnc@uca.edu
Courses
Taught:
Principles
of Biology I (Biology 1440)
Principles of Biology II (Biology 1441)
Economic Botany (Biology 3390)
Plant Ecophysiology (Biology 4450/5450)
Organisms in Extreme Environments (Biology 4412/5412)
Research:
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.
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