Photosynthesis Research

, Volume 24, Issue 1, pp 27–34 | Cite as

A vapor pressure deficit effect on crop canopy photosynthesis

  • W. T. Pettigrew
  • J. D. Hesketh
  • D. B. Peters
  • J. T. Woolley
Regular Paper


Canopy CO2-exchange rates (CER), air temperatures, and dew points were measured throughout ten days during the 1987 growing season for cotton (Gossypium hirsutum L.), grain sorghum [Sorghum bicolor (L) Moench], and five soybean [Glycine max (L) Merr.] cultivars, and throughout seven days in 1988, on maize (Zea maize L.). The objective was to determine if the decline in CER per unit light during the afternoon is associated with a vapor pressure deficit (VPD) increase. Some of the soybean and maize plots were kept as dry as possible. A VPD term significantly contributed (P≤0.05) to a canopy CER regression model in 54 of 80 data sets in 1987. Grain sorghum was less sensitive than the well-watered soybean genotypes to an increasing VPD (P≤0.05) on three of the ten measurement days and less sensitive than cotton (P≤0.05) on only one day. Cotton demonstrated less VPD sensitivity than soybean (P≤0.05) on one day. The moisture stressed soybean plots showed a greater CER sensitivity to VPD (P≤0.05) than the well-watered soybean plots. In 1988, the frequently irrigated maize plots were less sensitive to VPD (P≤0.05) than the rain-fed plots early in the season, before the rain-fed plots were excessively damaged by moisture stress. These results indicate that the afternoon declines in canopy CER found in a number of different species are associated with increases in the VPD; recent work of others suggests that this may be due to partial stomatal closure.

Key words

CO2-exchange rate Glycine max Gossypium hirsutum humidity hysteresis moisture stress Sorghum bicolor and Zea maize 



carbon dioxide exchange rate


vapor pressure deficit


photosynthetic photon flux density


days after planning


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Copyright information

© Kluwer Academic Publishers 1990

Authors and Affiliations

  • W. T. Pettigrew
    • 1
  • J. D. Hesketh
    • 2
  • D. B. Peters
    • 2
  • J. T. Woolley
    • 2
  1. 1.USDA-ARSStonevilleU.S.A.
  2. 2.USDA-ARSUniv. of IllinoisUrbanaUSA

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