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Crop Science Abstract -

Time Course of Photosynthesis and Stomatal Conductance Following Changes in Light Flux Density1


This article in CS

  1. Vol. 23 No. 4, p. 795-797
    Received: Oct 20, 1982

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  1. Tim Lloyd Setter and
  2. Brian A. Flannigan2



Natural fluctuations in light flux density occur in field conditions as a result of intermittent cloud cover. In this study photosynthetic CO2 exchange rates (CER) and leaf water vapor diffusive conductance (g3) were determined for the time course following light flux density transitions. Leaves of two maize hybrids at the grain-filling growth stage in field plots were enclosed in assimilation chambers and subjected to experimental increases and decreases in light flux density according to a prescribed schedule. Step increases in light required 2 to 3 min before steady-state CER were achieved. Stomatal opening occurring in response to the light increase showed a time course paralleling that for CER. In response to step decreases in light, photosynthetic rate declined rapidly to a new steady-state in less than 1 min while g3 continued to decline throughout the 4.3 min measurement period. The results show that water use efficiency for periods of fluctuating light was improved by rapid stomatal adjustment.

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