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LEAVES

The leaves are the stomach and lungs of the tree.

Their broad blades are a device to catch the sunlight which is needed in the process of digesting the food of the tree. The leaves are arranged on the twigs in such a way as to catch the most sunlight.

The leaves take up the carbonic acid gas from the air, decompose it under the influence of light and combine it with the minerals and water brought up by the roots from the soil.

The resulting chemical combinations are the sugars and starches used, by the cambium layer in building up the body of the tree.

A green pigment, chlorophyll, in the leaf is the medium by which, with the aid of sunlight, the sugars are manufactured.



CHLOROPHYLL

The chlorophyll gives the leaf its green color, and this explains why a tree pales when it is in a dying condition or when its life processes are interfered with.

The other colors of the leaf—the reds, browns and yellows of the fall or spring—are due to other pigments.

These are angular crystals of different hues, which at certain times of the year become more conspicuous than at others, a phenomenon which explains the variation in the colors of the leaves during the different seasons.

It is evident that a tree is greatly dependent upon its leaves for the manufacture of food and one can, therefore, readily see why it is important to prevent destruction of the leaves by insects or through over-trimming.

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

Leaf colors, such as reds, browns, and yellows, comes from many pigments, including shades of green from chlorophyll. In the autumn, the pigments of the reds, browns, yellows, and oranges become more conspicuous than the green of chlorophyll, causing the leaves of many deciduous trees to change color. The pigment chlorophyll plays an important role in generating energy for the trees and enabling them to grow.

Vocabulary

Chlorophyll: Any of a group of green pigments that are found in plants.
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.
Glucose: A simple sugar and a principle source of energy for cellular metabolism.

Concepts

PHOTOSYNTHESIS

Plants require the pigment chlorophyll and the additional items listed below to generate energy using photosynthesis:

  1. Sunlight
  2. Water from the ground
  3. Carbon dioxide gas from the air

Plants use these things for photosynthesis and create the following:

  1. Glucose/sugar as energy for the plant to grow
  2. Oxygen gas

Animals and plants enjoy a mutually beneficial relationship, as animals breathe in oxygen gas (O2) and breathe out carbon dioxide gas (CO2).

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: Can You Find It?

Review the diagram showing photosynthesis and find the following:

  • Light Energy
  • Carbon Dioxide Gas
  • Water
  • Chlorophyll
  • Sugar
  • Oxygen Gas

Activity 4: Take a Nature Walk

  • Bring a small collection bag and embark on a nature walk.
  • Collect multiple leaves of different colors.
  • Use the gathered specimens to create the field book entry.

Activity 5: Complete a Field Book Entry   

After your nature walk, complete pages 20-22 in 'Science Field Book for Fourth Grade.'

Review

Question 1

Why are leaves different colors?
1 / 4

Answer 1

The different pigments in leaves give them their different colors.
1 / 4

Question 2

What are three inputs for photosynthesis?
2 / 4

Answer 2

Water, carbon dioxide, and sunlight are needed for photosynthesis.
2 / 4

Question 3

What does photosynthesis output?
3 / 4

Answer 3

Photosynthesis outputs oxygen and sugar.
3 / 4

Question 4

Why do leaves of many deciduous trees turn from green to reds, browns, yellows, and oranges in the fall?
4 / 4

Answer 4

The pigments of the reds, browns, yellows, and oranges become more conspicuous in the fall.
4 / 4

  1. Why are leaves different colors? The different pigments in leaves give them their different colors.
  2. What are three inputs for photosynthesis? Water, carbon dioxide, and sunlight are needed for photosynthesis.
  3. What does photosynthesis output? Photosynthesis outputs oxygen and sugar.
  4. Why do leaves of many deciduous trees turn from green to reds, browns, yellows, and oranges in the fall? The pigments of the reds, browns, yellows, and oranges become more conspicuous in the fall.

References

  1. 'Studies of Trees' by Jacob Joshua Levison. gutenberg.org/ebooks/16116. n.p.
  2. 'Photosynthesis Image by Masroor.nida.ns. (CC BY-SA 4.0)' Wikimedia Commons. commons.wikimedia.org/wiki/File:Photosynthesis_Images.jpg. n.p.

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