Direct and indirect effects of light on stomata II. In Commelina communis L. |
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Authors: | J I L MORISON P G JARVIS |
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Institution: | Department of Forestry and Natural Resources, University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh EH9 3JU |
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Abstract: | Abstract. Two experiments are described which test the normal correlations that arise between stomatal conductance, net CO2 assimilation rate, and intercellular CO2 concentration (Ci), using whole shoots of Commelina communis L. In the first, conductance increased with decreasing Ci, at four different quantum flux densities, such that there was no unique relationship between conductance and quantum flux density or Ci, In the second, conductance increased hyperbolically with increasing quantum flux density while Ci was held constant at 466, 302, and 46 μmiolmol?1, and the response differed at each Ci. In neither experiment was conductance consistently related to net CO2 assimilation rate in the mesophyll. In both experiments high Ci suppressed the response of conductance to light, while there was a large response of conductance to light at low Ci, indicating an interaction between the effects of light and CO2 on stomata. The results show that the parallel responses of assimilation and conductance to light result in constant intercellular CO2 concentrations, and not that stomata maintain a 'constant Ci'. |
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Keywords: | stomata intercellular CO2 concentration light net CO2 assimilation rate |
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