(b) Transpiration : creates a suction force which pulls water inside the plant.
The diagram shows water vapour escaping from leaves through stomata — this is transpiration. Its key significance is that it creates a suction (transpiration pull) that draws water upward from roots through xylem. Options (a), (c), and (d) are incorrect as evaporation is a physical process, excretion refers to waste removal, and translocation involves transport of food, not water vapour loss.