Guard cells help in

Which element takes part in the opening and closing of stomata?

Define the location and function of the following:
$(1)$ Stomata
$(2)$ Matrix

The process of photosynthesis requires water. The system of xylem vessels from the root to the leaf vein can supply the needed water. But what force does a plant use to move water molecules into the leaf parenchyma cells where they are needed?

Transpiration increases by

According to the proton transport theory,which ion plays an important role in the opening and closing of stomata?