Descriptions and Structure
of Freshwater Aquarium Plants
The two main groups of plants are flowering and non-flowering
plants!
The majority of aquatic aquarium plants are flowering plants.
These plants can be grouped or categorized as: stem plants and rosette
plants. The plants which are not flowering plants can be grouped or categorized
as: ferns and mosses.
Note: For our purposes here, and to keep things simple, we are using flowering and non-flowering plants as our main groups. However as Travis Walker, a valuable contributor, has noted, "there are many other orders of plants not just flowering and non-flowering such as: Mosses, Algae, Fern Allies, Ferns, Conifers, Cycads and a few others each with their own unique adaptations for survival."
The structure of most of these plants includes:
Roots, stems, leaves, storage organs, and flowers (in the stem and rosette
groups).
Stems: The main stem of the plant is the aerial or above-ground stem. The aerial
stem then contains the stem axis, leaves, and flowers. The stem axis is
the main axis of all plants, and the tip of the stem is called a shoot
apex or vegetative point. The main functions of plant stems are transport
and support. Aquatic stems are much thinner and more flexible than land
plant stems, due to the support of the the surrounding water.
Here is more detailed information provided by Travis Walker:
- "Aerial Stem: Called a "petiole" because there are stems that grow underground (as well as others) called rhizomes (a potato is a good example).
- "Stem Axis: Known as the "Meristem" which is just a fancy word for a point at which growth occurs.
- "Shoot Apex: Also another form of "Meristem". The meristem that is the tallest is said to have "Apical Dominance" due to a hormone that runs down the stem to suppress growth of the other "Meristems". The Storage Organs are not usually referred to as these because the organs such as "Spongy Mesophyll" have many other functions other than storage of energy.
- "The Rosette Plants are known as "Monocots" or having one meristem and The Stem Plants are known as "Dicots" or having multiple meristems; both of which are in the order of flowering plants."
Leaves: Leaves then come from thickened areas on the stem axis called nodes. The
top of the leaves contains the chlorophyll, which is where photosynthesis
takes place. Stomata are on the underside of the leaves - the place where
gases are exchanged. However, in aquatic plants, stomata are often not
present - instead gas exchange occurs over the entire surface area of
the plant. Most flowers are produced above the water surface, to make
it easier for them to pollinate and spread.
Storage Organs: Plants also have storage organs where they can store the starch they make.
Storage organs can be located in several areas, including the leaves,
the stem axis, and the roots. The reproductive organs are located on the
top of the stem axis. The male organs are the stamens, and the female
organs are the carpels. There are generally asexual leaves or petals surrounding
them.
Roots: The roots are the part of the plant that are below ground - they anchor
the plant and receive nutrients from the soil.
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