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The impact of elevated carbon dioxide on the growth and gas exchange of three C 4 species differing in CO 2 leak rates
Author(s) -
Ziska Lewis H.,
Sicher Richard C.,
Bunce James A.
Publication year - 1999
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.1999.105112.x
Subject(s) - photosynthesis , carbon dioxide , c4 photosynthesis , botany , rubisco , panicum , nutrient , biology , chemistry , horticulture , zoology , ecology
Recent work has suggested that the photosynthetic rate of certain C 4 species can be stimulated by increasing CO 2 concentration, [CO 2 ], even under optimal water and nutrients. To determine the basis for the observed photosynthetic stimulation, we tested the hypothesis that the CO 2 leak rate from the bundle sheath would be directly related to any observed stimulation in single leaf photosynthesis at double the current [CO 2 ]. Three C 4 species that differed in the reported degree of bundle sheath leakiness to CO 2 , Flaveria trinervia , Panicum miliaceum , and Panicum maximum , were grown for 31–48 days after sowing at a [CO 2 ] of 350 μl l −1 (ambient) or 700 μl l −1 (elevated). Assimilation as a function of increasing [CO 2 ] at high photosynthetic photon flux density (PPFD, 1 600 μmol m −2 s −1 ) indicated that leaf photosynthesis was not saturated under current ambient [CO 2 ] for any of the three C 4 species. Assimilation as a function of increasing PPFD also indicated that the response of leaf photosynthesis to elevated [CO 2 ] was light dependent for all three C 4 species. The stimulation of leaf photosynthesis at elevated [CO 2 ] was not associated with previously published values of CO 2 leak rates from the bundle sheath, changes in the ratio of activities of PEP‐carboxylase to RuBP carboxylase/oxgenase, or any improvement in daytime leaf water potential for the species tested in this experiment. In spite of the simulation of leaf photosynthesis, a significant increase in growth at elevated [CO 2 ] was only observed for one species, F. trinervia . Results from this study indicate that leaf photosynthetic rates of certain C 4 species can respond directly to increased [CO 2 ] under optimal growth conditions, but that the stimulation of whole plant growth at elevated carbon dioxide cannot be predicted solely on the response of individual leaves.