Wetland plants grow submerged in water, either partially (e.g., water hyacinth) or completely (e.g.,
pond weeds), and show various adaptations to this habitat. Typically, there are numerous air spaces inside the stems, leaves, and roots; these aid gas exchange and buoyancy. Submerged parts generally have no cuticle (waterproof covering), enabling the plants to absorb minerals and gases directly from the water; in addition, being supported by the water, they need little of the supportive tissue found in land plants. Stomata, the gas exchange pores, are absent from plants that are completely submerged; in partially submerged plants with floating leaves (e.g., water lilies), stomata are found on the upper
leaf surfaces, where they cannot be flooded.
