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Foliar gas exchange responses of two deciduous hardwoods during 3 years of growth in elevated CO 2 : no loss of photosynthetic enhancement
Author(s) -
GUNDERSON C. A.,
NORBY R. J.,
WULLSCHLEGER S. D.
Publication year - 1993
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.1993.tb00501.x
Subject(s) - photosynthesis , stomatal conductance , carbon dioxide , acclimatization , deciduous , transpiration , water use efficiency , abscission , canopy , photosynthetic capacity , botany , horticulture , biology , chemistry , ecology
Responses of photosynthesis and stomatal conductance were monitored throughout a 3‐year field exposure of Liriodendron tulipifera (yellow‐poplar) and Quercus alba (white oak) to elevated concentrations of atmospheric CO 2 . Exposure to atmospheres enriched with +150 and +300 umol mol ‐1 CO 2 increased net photosynthesis by 12–144% over the course of the study. Net photosynthesis was consistently higher at +300 than at +150 umol mol ‐1 CO 2 . The effect of CO 2 enrichment on stomatal conductance was limited, but instantaneous leaf‐level water use efficiency increased significantly. No decrease in the responsiveness of photosynthesis to CO 2 enrichment over time was detected, and the responses were consistent throughout the canopy and across successive growth flushes and seasons. The relationships between internal CO 2 concentration and photosynthesis (e.g. photosynthetic capacity and carboxylation efficiency) were not altered by growth at elevated concentrations of CO 2 . No alteration in the timing of leaf senescence or abscission was detected, suggesting that the seasonal duration of effective gas‐exchange was unaffected by CO 2 treatment. These results are consistent with data previously reported for these species in controlled‐environment studies, and suggest that leaf‐level photosynthesis does not down‐regulate in these species as a result of acclimation to CO 2 enrichment in the field. This sustained enhancement of photosynthesis provides the opportunity for increased growth and carbon storage by trees as the atmospheric concentration of CO 2 rises, but many additional factors interact in determining whole‐plant and forest responses to global change.