OF WETLAND PLANTS
GOAL: To enable students to demonstrate the process of science by posing questions and investigating phenomena through language, methods, and instruments of science.
To enable students to develop an understanding of how environmental aspects affect life.
OBJECTIVES 1. Compare and Contrast oxygen transport of land plants
and wetland plants
Theme 1.3: The acquiring, recording, arranging and storing of information must be performed in a complete, accrurate, concise, and user friendly manner.
2. Identify circumstance for which wetland plants have
developed their adaptations.
Theme 1.4: Data should be examined to find patterns and relationships that may sugguest cause and effect or supoport inferences and hypotheses.
There are four beakers containing water and a plant. Two of the plants looks healthy and the other two look wilty and on the verge of death, with one looking worse than the other. On each beaker is a label indicating the salinity of the water in the beaker. One healthy plant has 0.0% salinity and the other has 3.5%, the next one has 1.5% salinity, and the worse looking one has 3.5% salinity.
What has happened to these plants? They all three are in water, received the same amount of light.
What is the one thing that was different in the plants? Salinity is different among the three plants
What do we observe happening regarding, in general, the appearance of the plants verses the salinity? The plants look worse the greater the salinity of the water, except for the healthy plant in the 3.5% water.
Why do you think that plant remains healthy even though it is in salty water? It must have something helping it maintain that the other three plants do not. It is adapted to live in salt water and the others are not so it doesn't die or wilt when placed in it for a few days.
What adaptations do you think this plant must need to survive in this environment?
Wetland plants are referred to as hydrophytic plants because they live in water. These plants are herbaceous, shrubs, or trees that have developed a special adaptation that enable them to survive the stressful conditions characteristic of wetlands such as:
1. fluctuations in water levels
2. permanent saturation with water
3. decreased oxygen
There are many types of wetland plants:
- Phytoplankton: this is a microscopic algae and chlorophyll containing bacteria that liveon or near the surface of the water.
It is phytoplankton that produces the majority of the world's oxygen and are the basis for any aquatic food chain.
- Herbaceous plants: these are nonwoody plants and can be categorized by their location in the water:
Emergent plants are erect plants that are rooted in sediment but extend out of the water. These include cattails, and reeds.
Floating plants may be either free-floating or rootedin the soil. Their leaves, flowers, and fruit float on the surface of water. An example is
Frog in duckweed
Submergent plants grow completely under the surface of the water.
- Shrubs: these ar low,woody plants that are less than 20 feet high and have permanent stems instead of a single trunk.
ADAPTATIONS OF WETLAND PLANTS
1. Many wetland plants have special air or pore spaces in their roots and stems called aerenchyma through which oxygen can enter the plant and be transported to its roots.
2. Some plants have hollowed stems that transport oxygen to the roots
3. Woody plants pump oxygen from their stems to their roots.
4. Many wetland trees have very shallow root systems, swollen trunks, or roots that grow above the ground. Examples of this are the cypress knees seen in swamps.
5. Some plants develop adaptations that allow them to tolerate salt water. These plants are called halophytes. Some adaptations of these plants are:
- develop ways to reduce salt intake by the roots called salt water exclusion
- some take the salt in but have salt-secreting glands to remove the salt
- Some develop salt concentrating glands like fleshy leaves. They collect salt in these leaves and then shed them
- Some plants have succulent leaves, store water, and then use it to dilute the concentration of salt
- Some plants have salt water proofed theirselves by developing a waxy covering
- Some reduce their leaf surface to minimize exposure to salt
- some isolate salt into internal organs
COMMON PLANTS OF COASTAL SALT AND BRACKISH MARSHES
COMMON NAME Smooth Cordgrass Glasswort Prickly Pear Bayberry (wax myrtle) Bid Cordgrass Swithgrass Spike Rushes Knotgrasses
Now that we know that we know what some of the adaptations are that allow wetland plants to live in their aquatic environment, let's experiment with this and see how it works.
Stems from the following
- water-lily (freshwater)
-Spartima alterniflora (saltwater)
1. Lay each stem in front of you and observe
2. Cut a 1-inch section of each and observe under the magnifying glass
3. Cut this small piece of stem lengthwise. Describe it
4. Fill the glass 3/4 full of water
5. Place each stem, one at a time, in the water. Blow into the stem. Describe what happen
Based on your observations, explaing how wetland plants are adapted to transfer oxygen to thier roots.
Where in Tennessee do you think plants might have developed adaptations to survive their climate and environment?
Plants that live on mountain tops in the Great Smoky Mountains National Park have developed adaptations to help them survive the strong
winds and cold climate. Many trees do not grow as tall to avoid contact with the wind and many of them may have needles instead of leaves
to conserve heat and water in the cold dry climates.
- Students will be given an exam in which a particular situation (such as decreased oxygen, increased water heighth, etc) and must provide an adaptation that could help the plant overcome that obstacle and explain the process.
Tennessee State Science Framework
Olsen, Margaret. "Georgia's Wetland Treasures". pp 38-44. United State Environmental Protection Agency.