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Aquarium Plant Description and Structure

Plant Types, Parts of a Plant and Plant Growth

Flowering and Non-Flowering Plants
Flowering Plants:   Rosette Plant (left) - Stem Plant (right)
Non-Flowering Plant:   Java Fern (center)Microsorum pteroptusPhoto © Animal-World

   Two main groups of plants are flowering and non-flowering plants!

   Plants live in all sorts of environments ranging from those that we see all around us and are familiar with, to those plants that live in incredible, far out places. Plants can be found from the desert to the arctic tundra, in bubbling hot springs to the depths of the ocean, in lakes, marshes and fast moving streams, with some even found living on other plants, like the bark of trees.

   There are several hundred thousand plants found all around the world, yet only about 200 species are suitable as aquarium plants. Most of the aquatic plants are decendents of terrestrial plants. There are around 1,600 kinds of water-loving plants (excluding the algae types), but not all water loving plants make good aquarium plants.

   Many water loving plants simply grow too big to be kept in the aquarium or need too much light. Of the approximately 200 plant species that are actually good candidates for the aquarium, only about 100 of those are available to the aquarium hobbyists.

Types of Plants Suitable for Aquarium Use    Of the water loving aquarium plants, there are true aquatic plants, amphibious plants, and land plants. Relatively few of the aquarium plants that are available for the aquarium are strictly aquatic.

• Aquatic Plants:
  Strictly aquatic plants have completely lost their ability to live on land. True aquatic plants include the bunch plants such as the Hornworts, Vallisnerias, Duck Weeds, Water Lilies, and Aponogetons.
  
  
• Amphibious Plants:
  Many favorite aquarium plants, such as the Swordplants, are what is known as amphibious. This means they are highly adaptable to fluctuating water conditions, and can live entirely submerged for long periods of time. These plants cannot actually compete with terrestrial plants, so are never found far from water.
  
  
• Land Plants::
  Finally there are the land plants, which are not fully adaptable to being submerged. Some of these, like the Water Orchid and the Brazilian Fern, will hold up under water for a long time, but they cannot grow in an aquarium.

Plant Structure
   The structure of most of the aquarium plants includes: roots, stems, leaves, storage organs, and flowers (in the stem and rosette groups). Both Rosette Plants and Stem Plants are in the order of flowering plants. Actually, the majority of aquatic aquarium plants are types of flowering plants
   For our purposes here, and to keep things simple, we are using flowering and non-flowering plants as our main groups in describing plant structure and growth. 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.

• 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. There are other types of stems as well. Those that grow underground are called rhizomes. A potato is a good example of a rhizome. Ferns, also examples of rhizomes, produce roots from rhizomes.
     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.
  
  Aerial Stem:The aerial or above-ground stem, called the Aerial Stem, is a stem with an erect or vertical growth habit above the ground.
  Petiole: The petiole is the small stalk attaching the leaf blade to the stem.
  Stem Axis: The stem axis Is known as the "Meristem" which is just a fancy word for a point at which growth occurs. It refers to the tissue on plants where growth can take place.
  Rosette Plants are known as "Monocots" or having one meristem
  Stem Plants are known as "Dicots" or having multiple meristems
  

   The primary meristem, called the apical meristem, are responsible for the primary plant growth. The apical meristem, or growing tip, is found in the buds and growing tips of roots in plants. Apical meristems are found in two locations: the root and the stem. There are several specific apical meristems including: Shoot apical meristems (shoot apex), Root apical meristems, Intercalary meristems, Floral meristems.

• 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.

Plant Growth:    The primary plant growth occurs where there is Apical dominance. This is when one meristem prevents or inhibits the growth of other meristems. Often there is one dominant apical meristem, but if it is removed, or is incomplete, then branching occurs leading to a bushy growth.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.

To learn about individual types of plants, see:

• Ferns and Mosses, Non-Flowering Aquarium Plants, Rhizomes
• Rosette Plants, Flowering Aquarium Plants, Floating Plants
• Aquarium Stem Plants, Flowering Aquarium Plants
  

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