Effects of elevated CO sub(2) on the tolerance of photosynthesis to acute heat stress in C sub(3), C sub(4), and CAM species

• Published in: American journal of botany Vol. 95; no. 2; pp. 165 - 176
• Main Authors: Wang, Dan, Heckathorn, Scott A, Barua, Deepak, Joshi, Puneet, Hamilton, EWilliam, LaCroix, Jacob J
• Format: Journal Article
• Language: English
• Published: 01-02-2008
• ISSN: 0002-9122

Determining the effect of elevated CO sub(2) on the tolerance of photosynthesis to acute heat stress (AHS) is necessary for predicting plant responses to global warming because photosynthesis is heat sensitive and AHS and atmospheric CO sub(2) will increase in the future. Few studies have examined this effect, and past results were variable, which may be related to methodological variation among studies. In this study, we grew 11 species that included cool and warm season and C sub(3), C sub(4), and CAM species at current or elevated (370 or 700 ppm) CO sub(2) and at species-specific optimal growth temperatures and at 30 degree C (if optimal [ne] 30 degree C). We then assessed thermotolerance of net photosynthesis (P sub(n)), stomatal conductance (g sub(st)), leaf internal [CO sub(2)], and photosystem II (PSII) and post-PSII electron transport during AHS. Thermotolerance of P sub(n) in elevated (vs. ambient) CO sub(2) increased in C sub(3), but decreased in C sub(4) (especially) and CAM (high growth temperature only), species. In contrast, elevated CO sub(2) decreased electron transport in 10 of 11 species. High CO sub(2) decreased g sub(st) in five of nine species, but stomatal limitations to P sub(n) increased during AHS in only two cool-season C sub(3) species. Thus, benefits of elevated CO sub(2) to photosynthesis at normal temperatures may be partly offset by negative effects during AHS, especially for C sub(4) species, so effects of elevated CO sub(2) on acute heat tolerance may contribute to future changes in plant productivity, distribution, and diversity.