How Abscisic Acid Causes Depressions of the Photosynthetic Capacity of Leaves
When a solution of ABA is fed into an illuminated leaf, stomata begin to close about 10 min later and the rate of CO2 assimilation, A, declines. Simultaneous measurements of water-vapor loss and CO2 uptake allow the computation of the intercellular partial pressure of CO2, ci. Such computations showed that often ci remained constant when the assimilation rate decreased in response to an application of ABA. Apparently, ABA had affected the photosynthetic machinery directly to an extent that the CO2 available in the leaf was used with reduced efficiency [1, 9]. This phenomenon was observed to occur in leaves of numerous species, monocots as well as dicots, and employing the C3 as well as the C4 mechanisms of photosynthesis . In this contribution will be explained how application of ABA can cause depressions of photosynthesis at apparently constant computed ci.
KeywordsAbscisic Acid Stomatal Conductance Photosynthetic Capacity Assimilation Rate Stomatal Aperture
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