Journal Article

Low temperature effects on leaf physiology and survivorship in the C<sub>3</sub> and C<sub>4</sub> subspecies of <i>Alloteropsis semialata</i>

Colin P. Osborne, Emily J. Wythe, Douglas G. Ibrahim, Matthew E. Gilbert and Brad S. Ripley

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 59, issue 7, pages 1743-1754
Published in print May 2008 | ISSN: 0022-0957
Published online April 2008 | e-ISSN: 1460-2431 | DOI: http://dx.doi.org/10.1093/jxb/ern062
Low temperature effects on leaf physiology and survivorship in the C3 and C4 subspecies of Alloteropsis semialata

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The species richness of C4 grasses is strongly correlated with temperature, with C4 species dominating subtropical ecosystems and C3 types predominating in cooler climates. Here, the effects of low temperatures on C4 and C3 grasses are compared, controlling for phylogenetic effects by using Alloteropsis semialata, a unique species with C4 and C3 subspecies. Controlled environment and common garden experiments tested the hypotheses that: (i) photosynthesis and growth are greater in the C4 than the C3 subspecies at high temperatures, but this advantage is reversed below 20 °C; and (ii) chilling-induced photoinhibition and light-mediated freezing injury of leaves occur at higher temperature thresholds in the C4 than the C3 plants. Measurements of leaf growth and photosynthesis showed the expected advantages of the C4 pathway over the C3 type at high temperatures. These declined with temperature, but were not completely lost until 15 °C, and there was no evidence of a reversal to give a C3 advantage. Chronic chilling (5–15 °C) or acute freezing events induced a comparable degree of photodamage in illuminated leaves of both subspecies. Similarly, freezing caused high rates of mortality in the unhardened leaves of both subtypes. However, a 2-week chilling treatment prior to these freezing events halved injury in the C3 but not the C4 subspecies, suggesting that C4 leaves lacked the capacity for cold acclimation. These results therefore suggest that C3 members of this subtropical species may gain an advantage over their C4 counterparts at low temperatures via protection from freezing injury rather than higher photosynthetic rates.

Keywords: Alloteropsis semialata; C3 photosynthesis; C4 photosynthesis; chilling; cold acclimation; freezing; photodamage; quantum yield; temperature

Journal Article.  8637 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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