Which type of aquatic plants are characterized by their leaf stems not being submerged?

Emergent aquatic plants are unique because they have leaf stems that extend above the water's surface, allowing the leaves to be exposed to the air while their roots remain submerged in the water. This characteristic distinguishes them from other types of aquatic plants. Submersed plants, in contrast, are completely underwater, meaning their leaf stems and leaves do not come above the surface at all. Floating plants remain on the water's surface, but their leaves typically float on top, rather than having stems that rise up from the water. Terrestrial plants, while they may be found near aquatic environments, do not possess the adaptations required to thrive in an aquatic setting since they are primarily adapted to grow on land. Therefore, emergent plants specifically have the adaptation of rising above the water, making them the correct choice in this context.