Characteristics of a Freshwater Environment Water is plentiful, at least during the growing season. Oxygen concentration of oxygen in the water and in thick tissues of the underwater plant is low. Minerals and nutrients are scarce or dilute within the water medium, as compared with drier soil. Types of Leaves Many of the designs exhibited by plants living in water were obvious to early botanists. For example, Agnus Arber published a book in 1920 on aquatic plants, documenting many of the strategies that we still talk about today.
Light penetration is especially poor in turbid water with dense surface populations of algae.
On these leaves, stomates are generally absent, and would be useless for submerged plants, where water, not air, continually surrounds the photosynthetic organ. Intercellular air spaces are not well developed, thereby enabling this plant to remain submersed by having greater specific gravity. In swiftly running streams, these shoots and leaves wave and dance wildly. Floating leaves tend to be much broader, without major lobing, and remain flat on the water, taking advantage of full sun. The upper leaf surface tends to have a very prominent cuticle, thereby permitting water to roll off, and not interfering with photosynthesis or promoting growth of epiphytic algae.