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Elevated atmospheric CO 2 alters stomatal responses to variable sunlight in a C 4 grass
Author(s) -
KNAPP A. K.,
FAHNESTOCK J. T.,
OWENSBY C. E.
Publication year - 1994
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.1365-3040.1994.tb00282.x
Subject(s) - stomatal conductance , sunlight , andropogon , shading , transpiration , chemistry , horticulture , canopy , photosynthesis , botany , atmospheric sciences , biology , art , physics , astronomy , visual arts , geology
Native tallgrass prairie in NE Kansas was exposed to elevated (twice ambient) or ambient atmospheric CO 2 levels in open‐top chambers. Within chambers or in adjacent unchambered plots, the dominant C 4 grass, Andropogon gerardii , was subjected to fluctuations in sunlight similar to that produced by clouds or within canopy shading (full sun > 1500 μmol m −2 s −1 versus 350 μmol m −2 s −1 shade) and responses in gas exchange were measured. These field experiments demonstrated that stomatal conductance in A. gerardii achieved new steady state levels more rapidly after abrupt changes in sunlight at elevated CO 2 when compared to plants at ambient CO 2 . This was due primarily to the 50% reduction in stomatal conductance at elevated CO 2 , but was also a result of more rapid stomatal responses. Time constants describing stomatal responses were significantly reduced (29–33%) at elevated CO 2 . As a result, water loss was decreased by as much as 57% (6.5% due to more rapid stomatal responses). Concurrent increases in leaf xylem pressure potential during periods of sunlight variability provided additional evidence that more rapid stomatal responses at elevated CO 2 enhanced plant water status. CO 2 ‐induced alterations in the kinetics of stomatal responses to variable sunlight will likely enhance direct effects of elevated CO 2 on plant water relations in all ecosystems.