The effect of vapor pressure deficit on diffusion resistance inOpuntia compressa

摘要

Measurements of the diffusion resistance ofOpuntiaplants that were growing in a controlled environment were made with a porometer to determine the effect of vapor pressure deficit (vpd) on the diurnal pattern of diffusion resistance. When the vpd was high during the light period and low in darkness, diffusion resistance was greater during the day than at night. However, when the vpd was low during the day, diffusion resistance was lower during the day than at night. Thus diffusion resistance ofOpuntia, at least under some conditions, is affected by the vpd of the atmosphere. This may explain the contradictory results that are reported by investigators working in different environments.