Sensitivity to far-red radiation in stomata of Phaseolus vulgaris L.: Rhythmic effects on conductance and photosynthesis |
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Authors: | M. G. Holmes J. C. Sager W. H. Klein |
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Affiliation: | (1) Smithsonian Environmental Research Center, 12441 Parklawn Drive, 20852 Rockville, MD, USA;(2) Department of Botany, University of Cambridge, Downing Street, CB2 3EA Cambridge, UK |
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Abstract: | The influence of far-red (FR; 700–800 nm) radiation on steady-state stomatal conductance and net photosynthesis in P. vulgaris has been studied. Whereas FR radiation alone was relatively ineffective, addition of FR to a background of white light (WL; predominantly 400–700 nm) resulted in increased stomatal conductance. Stomata exhibited a marked diurnal sensitivity to FR. The action maximum for enhancing stomatal conductance was near 714 nm. A combination of FR and infra-red (IR; >800 nm) enhanced net photosynthesis when added to a background of WL. When IR alone was added to WL, there was a net decrease in photosynthesis, indicating that it is the FR waveband which is responsible for the observed photosynthetic effects. Naturally occurring levels of FR radiation (235 mol·m-2·s-1) in vegetation-canopy shade enhanced net photosynthetic CO2 gain by 28% when added to a background of 55 mol·m-2·s-1 WL.Abbreviations BL blue - FR far-red - IR infra-red - PAR photosynthetically active radiation - R red - WL white light |
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Keywords: | Phaseolus (photosynthesis, stomatal opening) Photosynthesis (active radiation) Phytochrome and stomatal opening Stomatal opening Transpiration |
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