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Non‐uniform stomatal closure and the apparent convexity of the photosynthetic photon flux density response curve
Author(s) -
OLSSON T.,
LEVERENZ J. W.
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.tb00162.x
Subject(s) - photosynthesis , stomatal conductance , conductance , respiration rate , botany , flux (metallurgy) , respiration , convexity , transpiration , horticulture , atmospheric sciences , biology , physics , chemistry , organic chemistry , financial economics , economics , condensed matter physics
The photosynthetic response of leaves to photosynthetic photon flux density (PPFD) may be described by parameters for the rate of dark respiration ( R ), the initial slope (Ф), the PPFD‐saturated rate of net photosynthesis ( A mQ ) and the apparent convexity (θ a ). We tested the hypothesis that non‐uniformity in stomatal aperture across a leaf results in a clearly lower θ a because PPFD saturation will occur at different irradiances in different regions of the leaf. A computer model was constructed to simulate the effects of bell‐shaped and other distributions of stomatal conductance for CO 2 ( g s ) across a model leaf. In the model, Ф and A mQ decreased by up to 50% whereas θ a decreased by at most 8%, essentially negating the hypothesis. The relationship between photosynthetic rate and g s determined the size of the responses of θ a and Ф to non‐uniform g s . In support of the model, experiments on sunflower leaves showed that Ф and A mQ decreased by 32 and 52%, respectively, while no measurable change in θ a occurred, when abscisic acid was used to induce patchiness in g s . Although not all possible patterns of non‐uniform stomatal conductance have been tested, it appears that if large variations in θ a occur in nature they do not result from non‐uniform g s .