Answer:
Guard cells
Step-by-step explanation:
Guard cells are can be described as a special group of plant cells that are located or can be found in the epidermis of plants. They come in the shape of a kidney.
They help to control the rate at which air moves in and out of the plant, the is achieved by periodically opening the stoma and blocking it back. They are also responsible for the regulation of water movement in and out of the plant.
This essential material in which the guard cell regulates/ control is an important part of plant photosynthesis, therefore they play an important role in the process through which plants manufacture their food.