Chapter 1, Plants and their Parts
Lesson 3, the Importance of Plants
VOCABULARY
Photosynthesis
Respiration
Objectives:
 Explore how light affects the plant’s leaves.
 Describe the process of photosynthesis and respiration.
 Describe how roots, stems, and leaves work together to get water and minerals to all
parts of the plant.
 Understand the role of plants as food producers and oxygen suppliers.
MAIN IDEA:
Plants make food and produce oxygen through photosynthesis.
Pre knowledge  All living things need energy to survive. Animals get their energy from plants.
Plants make their own food. Where do plants get energy? From sunlight. LIGHT = ENERGY
1. What is Photosynthesis?
a. Light is a form of energy that plants use to make their own food.
b. Plants capture the energy of light and trap it in the foods they make.
c. Later, when they need this energy, they get it back from the food.
d. The FOOD MAKING PROCESS is called photosynthesis.
i. Greek for “putting together by light”
ii. This is a complex process, but to put it simply.
First, sunlight strikes a green part of a plant, the leaf
a.
b.
c.
d.
e.
f.
g.
h.
The leaf is green because of chlorophyll.
Chlorophyll helps the plant make its own food.
Chlorophyll is found in plant parts called chloroplasts.
The chloroplasts are like tiny chemical factories.
Inside water and CO2 combine to make sugar and oxygen.
This reaction happens because of SUNLIGHT
The sugars (food) the plants make stay in the plant
The oxygen the plant makes is released in the air.
Once the sun’s energy is trapped in the sugars that the
plant made, the plants cells use oxygen to break apart the
sugars, called respiration.
How is photosynthesis different from respiration?
During photosynthesis, plants change carbon dioxide and water into sugars and oxygen.
During respiration, plants and animals use oxygen to break down sugar to produce energy,
water, and carbon dioxide.
2. How Do Leaves Change Color?
a. Fall/autumn leaves change color, yellow, orange, and red.
i. All the yellows and oranges were in the plants leaves ever since
summer!!!!!
ii. You cannot see them because there was so much chlorophyll.
b. As temperatures drop the leaves stop making chlorophyll.
i. Slowly, the chlorophyll that remains begins to break down and then
vanishes.
3. How Does Water Get from Roots to Leaves?
a. Plants are made of 70-95% water
b. Cells in all parts of plants need water to carry out important chemical reactions
like photosynthesis.
c. They also need water to stay firm and not wilt.
d. Plants constantly lose water through transpiration.
Transpiration Process
1. Water and dissolved minerals enter the plant’s root hairs from the soil.
2. The water passes through the cortex of the root, enters the xylem, and travels up the
stem.
3. Transpiration up in the leaves helps draw the water into the xylem of the plant’s stem.
4. Water moves up the stem, through the leaf’s petiole, and into its veins. The veins carry
the water to the leaf’s cells.
5. Almost 99% of the water that entered the roots is given off into the air by transpiration
through the leaf’s stomata.