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Response of Stomatal Numbers to CO₂ and Humidity: Control by Transpiration Rate and Abscisic Acid
J. A. Lake and F. I. Woodward
The New Phytologist
Vol. 179, No. 2 (Jul., 2008), pp. 397-404
Stable URL: http://www.jstor.org/stable/25150459
Page Count: 8
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The observation that stomatal density (number mm⁻²) on herbarium leaves had decreased over the last century represents clear evidence that plants have responded to anthropogenic increases in CO₂ concentration. The mechanism of the response has proved elusive but here it is shown that density responses to both CO₂ concentration and humidity are correlated with changes in whole-plant transpiration and leaf abscisic acid (ABA) concentration. The transpiration rate of a range of accessions of Arabidopsis thaliana was manipulated by changing CO₂ concentration, humidity and by exogenous application of ABA. Stomatal density increased with transpiration and leaf ABA concentration. A common property of signal transduction systems is that they rapidly lose their ability to respond to the co-associated stimulus. Pathways of water movement within the plant are connected and so variations in supply and demand can be signalled throughout the plant directly, modifying stomatal aperture of mature leaves and stomatal density of developing leaves. Furthermore, the system identified here does not conform to the loss of ability to respond. A putative mechanism is proposed for the control of stomatal density by transpiration rate and leaf ABA concentration.
The New Phytologist © 2008 New Phytologist Trust