Why is it that guttation is most commonly observed in the morning?

Question

Knowing that guttation occurs through a plant's hydathodes due to root pressure forcing liquid water out of the leaves, I am curious as to why so many small drops of water are observable on plants in the morning. Could this potentially have to do with the moisture in the air at night vs day? Since humidity tends to increase at night? Thanks in advance!

Answer 1

The relative humidity is the ratio of the actual amount of water vapor in the air (absolute humidity in g/m³) to the maximum possible water vapor the saturated air can hold at that temperature. So, at night when temperature decreases and the air begins to cool, it can hold very little moisture which is seen mostly during the night and early morning time compared with warmer air during the daytime. Hence the quotient ( actual amount of water vapor) has a greater value when the temperature decreases explaining an increase in the relative humidity during the night and early morning time.

The rate of transpiration and relative humidity have an inverse relationship. When relative humidity increases, thereby increasing the moisture content in the atmosphere, the amount of water vapor released through the stomata (transpiration) decreases and the stomata close at night. But the water and nutrients still rise in the plant at night and early morning through the vascular system(Xylem and Phloem) by the action of root pressure( cool air and warm soil create a root pressure) and water intake exceeds evaporation rate( transpiration). In this situation, guttation occurs, which is considered a technique where the plant eliminates the excess and surplus water absorbed, through specialized water pores called hydathodes otherwise water pressure can build up in their tissues during the night and early morning. Hence guttation is more prominent during these times.