In aquatic plants, large air sacs provide them with buoyancy, allowing them to float in water. The large air sacs are surrounded by parenchyma tissue. Parenchyma is a type of simple plant tissue that is composed of thin-walled cells with a large central vacuole. It is the most common and versatile type of tissue in plants.

Parenchyma tissue is responsible for various functions in plants, including storage, photosynthesis, and gas exchange. In the case of aquatic plants, parenchyma cells in the air sacs contain air spaces that help in buoyancy. These air spaces contribute to the overall volume of the plant and enable it to remain buoyant in water.

Collenchyma tissue, option 2, is another type of simple plant tissue. However, it provides mechanical support and is not typically associated with air sacs or buoyancy effects.

Similarly, sclerenchyma tissue, option 3, is a type of plant tissue that provides structural support. It has thick cell walls and is not directly involved in buoyancy effects.

Option 4, complex tissue, is a broad term that refers to tissues composed of multiple types of cells. While complex tissues exist in plants, they are not specifically related