Chastain, Daryl , Hall, Trent , Brinker, Daniel , Choinski, John .
High leaf temperatures may induce elevated thermotolerance in young cotton leaves.
Previous research has documented increased photosynthetic thermotolerance and rapid recovery from heat damage in young leaves of various tree species, when compared to mature leaves. In this present study, we present evidence that young cotton leaves are similarly more tolerant to high leaf temperatures, but only for part of the growing season. During the early part of the season (50 days after planting, DAP) when the cotton canopy was open, young leaves were as much as 10 C warmer than mature leaves and 15 C above ambient air during periods of peak irradiance; this difference a consequence of reduced stomatal conductance values ~1/3 lower than mature leaves. During these periods of high thermal stress, (although chlorophyll content was lower) measurements of actual quantum yield of young leaves were similar to more mature leaves. Temperature response experiments done with detached leaves collected inthe field also showed photosynthetic thermal optima ~5 C warmer than mature leaves (35 C compared with 30 C for mature leaves). After canopy closure (83 DAP), leaf temperature and stomatal conductance was similar for all age classes, and pigments were comparable to open-canopy measurements, however actual quantum yield values of young leaves in the field were significantly lower than older leaves. Temperature response for detached leaves collected after canopy closure also differed from open-canopy leaves. In mature leaves, photosynthetic thermal optima broadened to 30-40 C, whereas young leaves optima decreased to 30 C (a decrease of 5 C). This effect may be due to microclimates formed by transpiration from nearby vegetative material resulting in a decreased vapor pressure deficit. We hypothesize that high leaf temperatures in young leaves may induce changes in leaf chemistry that can pre-adapt leaves to warmer, late-season air temperatures. We are currently investigating whether increased thermotolerance in young cotton leaves may be due a more thermally stable thylakoid membrane with higher lipid saturation levels.
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1 - University Of Central Arkansas, Biology Department, Conway, AR, 72035, UNITED STATES
3 - University of Central Arkansas, Biology, Conway, AR, 72035, USA
Presentation Type: Poster:Posters for Topics
Location: Battelle South/Convention Center
Date: Monday, July 9th, 2012
Time: 5:30 PM