Answer: The correct answer for the blank is - transpiration.
Transpiration can be described as the process of movement of water across plant and its evaporation in the environment primarily through leaves (with the help of small pores present on the leaves, called stomata).
Water is first absorbed from roots of the plants and then it is transported to various parts (along with essential minerals and nutrients).
Water is evaporated in the surrounding through leaves, stem, and flowers.
Thus, through the process of transpiration, plant adds water in the atmosphere.