Question

Compare the water loss rates from a lizard here in the desert during a typical early summer day and night. Assume that the aperture of the pores and any other openings (that allow water vapor loss) from the lizard are similar day and night. Also assume that the air vapor pressure is similar day and night (a reasonable assumption unless a storm system happens to come through). The temperature during the day is many degrees higher than at night. Assume the lizard's surface temperature is the same as its surrounding air temperature. The rate of water loss from the lizard would be much lower at night because the VPD is lower at night. Why is the VPD lower at night

Answer 1

Answer: The VDP ( Vapour Pressure Deficit) of the lizard is lower at night because lower nighttime lizard surface temperatures indicates that there is a lower saturation vapour pressure.

This lower saturation vapour pressure simply implies that there is a lower lizard to air vapour pressure Deficit.(VPD).

So assuming the surface temperature of the lizard is the same as its surrounding air temperature,this means that the rate of water loss from the lizard would be much lower during night because the vapour pressure deficit of the lizard is lower at night.