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Correlation of Stomatal Conductance with Photosynthetic Capacity of Cotton Only in a CO₂-Enriched Atmosphere: Mediation by Abscisic Acid?

John W. Radin, Wolfram Hartung, Bruce A. Kimball and Jack R. Mauney
Plant Physiology
Vol. 88, No. 4 (Dec., 1988), pp. 1058-1062
Stable URL: http://www.jstor.org/stable/4271710
Page Count: 5
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Correlation of Stomatal Conductance with Photosynthetic Capacity of Cotton Only in a CO₂-Enriched Atmosphere: Mediation by Abscisic Acid?
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Abstract

Some evidence indicates that photosynthetic rate (A) and stomatal conductance (g) of leaves are correlated across diverse environments. The correlation between A and g has led to the postulation of a "messenger" from the mesophyll that directs stomatal behavior. Because A is a function of intercellular CO2 concentration (ci), which is in turn a function of g, such a correlation may be partially mediated by ci if g is to some degree an independent variable. Among individual sunlit leaves in a cotton (Gossypium hirsutum L.) canopy in the field, A was significantly correlated with g (r2 = 0.41, n = 63). The relative photosynthetic capacity of each leaf was calculated as a measure of mesophyll properties independent of ci. This approach revealed that, in the absence of ci effects, mesophyll photosynthetic capacity was unrelated to g (r2 = 0.06). When plants were grown in an atmosphere enriched to about 650 microliters per liter of CO2, however, photosynthetic capacity remained strongly correlated with g even though the procedure discounted any effect of variable ci. This "residual" correlation implies the existence of a messenger in CO2-enriched plants. Enriched CO2 also greatly increased stomatal response to abscisic acid (ABA) injected into intact leaves. The data provide no evidence for a messenger to coordinate g with A at ambient levels of CO2. In a CO2-enriched atmosphere, though, ABA may function as such a messenger because the sensitivity of the system to ABA is enhanced.

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