Humidity Response Curves
Humidity or Vapor Pressure Deficit (VPD) response curves measures the plant response to changing water vapor. Stomatal dynamics in response to H2O concentration can be studied without altering photosynthetic assimilation. Click here for more information on how the LI-6400XT controls humidity.
Controlling Temperature and HumidityWatch Webinar
Stomatal and photosynthetic response to vapor pressure deficit (VPD, difference in vapor pressure between leaf and chamber air). The photosynthetic rate (dashed lines) and stomatal conductance (solid lines) were measured at steady state over a range of VPD's as driven by changing the water mole fraction in the chamber. Intact leaves were measured in an experimental garden at growth CO2 and 1300 µmol m-2 s-1 until steady state was reached at each water mole fraction. Helianthus annuus (Sunflower, blue) and Glycine max (Soybean, orange) had very different (~10x) stomatal conductances and the percentage decreases in stomatal conductance were greater in sunflower.