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Effects of elevated CO 2 on the tolerance of photosynthesis to acute heat stress in C 3 , C 4 , and CAM species
Author(s) -
Heckathorn Scott A.,
Barua Deepak,
Joshi Puneet,
Hamilton E. William,
LaCroix Jacob J.
Publication year - 2008
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.3732/ajb.95.2.165
Subject(s) - photosynthesis , stomatal conductance , biology , photosystem ii , acclimatization , electron transport chain , heat stress , botany , horticulture , zoology
Determining the effect of elevated CO 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 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 3 , C 4 , and CAM species at current or elevated (370 or 700 ppm) CO 2 and at species‐specific optimal growth temperatures and at 30°C (if optimal ≠ 30°C). We then assessed thermotolerance of net photosynthesis ( P n ), stomatal conductance ( g st ), leaf internal [CO 2 ], and photosystem II (PSII) and post‐PSII electron transport during AHS. Thermotolerance of P n in elevated (vs. ambient) CO 2 increased in C 3 , but decreased in C 4 (especially) and CAM (high growth temperature only), species. In contrast, elevated CO 2 decreased electron transport in 10 of 11 species. High CO 2 decreased g st in five of nine species, but stomatal limitations to P n increased during AHS in only two cool‐season C 3 species. Thus, benefits of elevated CO 2 to photosynthesis at normal temperatures may be partly offset by negative effects during AHS, especially for C 4 species, so effects of elevated CO 2 on acute heat tolerance may contribute to future changes in plant productivity, distribution, and diversity.