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6. INFLUENCE OF AIR

On the underside of leaves and on other surfaces of a tree little pores known as stomata may be found.
Leaf Stomata
In the bark of birch and cherry trees these openings are very conspicuous and are there known as lenticels.
Cherry Tree Lenticels
These pores are necessary for the breathing of the tree (respiration), whereby carbonic acid gas is taken in from the air and oxygen given out.
Photosynthesis
The process of assimilation depends upon this breathing process and it is therefore evident that when the stomata are clogged as may occur where a tree is subjected to smoke or dust, the life processes of the tree will be interfered with.
Industrial Pollution
The same injurious effect results when the stomata of the roots are interfered with. Such interference may occur in cases where a heavy layer of soil is piled around the base of a tree, where the soil about the base of a tree is allowed to become compact, where a tree is planted too deep, or where the roots are submerged under water for any length of time.
Flooded Tree Roots
In any case the air cannot get to the roots and the tree suffers.

Nature takes special cognizance of this important requirement in the case of cypress trees, which habitually grow under water. Here the trees are provided with special woody protuberances known as "cypress knees," which emerge above water and take the necessary air.
Cypress Knees

Directions

Study the lesson for one week.

Over the week:

  • Read the lesson.
  • Review the synopsis.
  • Recite aloud the vocabulary words and their definitions.
  • Learn the concepts.
  • Complete the enrichment activities.
  • Study the review questions.

Synopsis

This lesson overviews air as a requirement of trees. Trees take carbon dioxide gas in from the air and expel oxygen gas out through stomata and lenticels. Stomata are small pores on the underside of leaves, and lenticels are openings in the bark of certain trees. Trees may be injured if their ability to exchange gases with the air is hindered by pollution or flooding.

Vocabulary

Stomata: The tiny pores in the epidermis of a leaf or stem through which gases and water vapor pass.
Lenticel: One of many raised pores in the stem of a woody plant that allows gas exchange between the atmosphere and the internal tissues.
Photosynthesis: Any process by which plants convert light energy into chemical energy.
Oxygen Gas (O2): Molecular oxygen, a colorless, odorless gas at room temperature.
Carbon Dioxide Gas (CO2): A colorless, odorless gas formed during respiration and combustion and consumed by plants during photosynthesis.
Cypress Knees: A woody projection forming above the roots of certain cypress species, perhaps to aid in oxygenation to the roots or to anchor the tree in soft, muddy soil.
Atmosphere: The gases surrounding the Earth.

Concepts

OUR ATMOSPHERE

The Earth's atmosphere encompasses the Earth, shielding its living organisms from the following hazards:

  1. Cosmic Rays: A stream of energetic particles originating outside our solar system.
  2. Solar Wind: The outflow of charged particles from the sun into space
  3. Ultraviolet Radiation: Electromagnetic radiation beyond (higher in frequency than) light visible to the human eye

The Earth's atmosphere contains the following gases and their percentages:

  1. Nitrogen (78%)
  2. Oxygen (21%)
  3. Argon (0.9%)
  4. Carbon Dioxide (.04%)
  5. Trace amounts of other gases.

Find a nitrogen molecule (N2), an oxygen molecule (O2), a carbon dioxide molecule (CO2), and a water molecule (H2O) in the image below.

As you know, plants take in carbon dioxide and expel oxygen to/from the atmosphere, while humans do the reverse.

Enrichment

Activity 1: Narrate the Lesson

  • After reading or listening to the lesson, narrate the lesson aloud using your own words.

Activity 2: Study the Lesson Pictures

  • Study the lesson pictures and describe how they relate to the lesson.

Activity 3: Examine the Layers of the Earth's Atmosphere

The Earth's atmosphere can be divided into layers.

Zoom in to study the image of the layers of the Earth's atmosphere and to answer the following:

  • How many layers are shown on the diagram?
  • What is the name of the layer closest to Earth?
  • What is the name of the layer farthest from Earth?
  • Into which layer does the highest mountain on Earth (Mount Everest) reach?
  • In which layer did the space shuttle orbit?
  • Into which layer can a weather balloon ascend?
  • In which layer does the Aurora Borealis (Northern Lights) glow?

Activity 4: Take a Nature Walk

  • Bring a small sketchbook and embark on a nature walk.
  • Study the form and habitat of any tree of your choice.
  • Use the gathered information and sketches to create the field book entry.

Activity 5: Complete a Field Book Entry   

After your nature walk, complete page 35 in 'Science Field Book for Fourth Grade.'

Review

Question 1

Through what openings do trees exchange carbon dioxide and oxygen with the air?
1 / 5

Answer 1

Trees exchange carbon dioxide and oxygen with the air using their stomata and lenticels.
1 / 5

Question 2

What consists of 78 percent nitrogen, 21 percent oxygen, and other gases?
2 / 5

Answer 2

The atmosphere consists of 78 percent nitrogen, 21 percent oxygen, and other gases.
2 / 5

Question 3

How does the atmosphere protect living organisms from harm?
3 / 5

Answer 3

The atmosphere shields living things from cosmic rays, solar wind, and harmful radiation coming from outer space.
3 / 5

Question 4

Which gas do trees take in?
4 / 5

Answer 4

Trees take in carbon dioxide gas.
4 / 5

Question 5

Which gas do trees expel
5 / 5

Answer 5

Trees expel oxygen gas.
5 / 5

  1. Through what openings do trees exchange carbon dioxide and oxygen with the air? Trees exchange carbon dioxide and oxygen with the air using their stomata and lenticels.
  2. What consists of 78 percent nitrogen, 21 percent oxygen, and other gases? The atmosphere consists of 78 percent nitrogen, 21 percent oxygen, and other gases.
  3. How does the atmosphere protect living organisms from harm? The atmosphere shields living things from cosmic rays, solar wind, and harmful radiation coming from outer space.
  4. Which gas do trees take in? Trees take in carbon dioxide gas.
  5. Which gas do trees expel Trees expel oxygen gas.

References

  1. 'Studies of Trees' by Jacob Joshua Levison. gutenberg.org/ebooks/16116. n.p.
  2. 'Atmosphere.' Wikipedia. Wikipedia.org. n.p.

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