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Crop Science Abstract -

Water Use Efficiency of Cassava. I. Effects of Air Humidity and Water Stress on Stomatal Conductance and Gas Exchange1


This article in CS

  1. Vol. 24 No. 3, p. 497-502
    Received: Jan 3, 1983

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  1. Mabrouk A. El-Sharkaway and
  2. James H. Cock2



Measurements of CO2 and H2O exchange of attached cassava (Manihot esculenta Crantz) leaves in water stressed and control plants of cultivars M Col 90 and M Col 88 were made at various leaf-air vapor pressure differences (VPD) (0.8 to 4.5 kPa). Apparent photosynthesis and transpiration were sharply reduced by increase in VPD above 1.8 to 2.0 kPa in both stressed and nonstressed plants. This trend coincided with changes in leaf conductance over similar ranges of VPD. The rapid closure of stomata in dry air was independent of bulk leaf water potential (ψl). Furthermore, the response was completely reversible in humid air after short exposure to dry air, suggesting a direct response to changes in air humidity. Water use efficiency decreased as VPD increased over the range of 1 to 4 kPa. The significance of the Stomatal response to humidity is discussed in relation to WUE in long dry periods.

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