When plants don’t get enough water, they close their stomata– tiny openings in leaves that allow carbon dioxide in and oxygen out. What effect will this have on photosynthesis?

Question

A diagram of a leaf showing the role of stomata in gas exchange during photosynthesis. The main image shows the leaf with a circled area magnified on the right. The magnified section reveals plant cells and stomata, which are small openings. Arrows illustrate the intake of carbon dioxide (CO2) through an open stoma and the release of oxygen (O2) through another. A closed stoma is also indicated.

A
Photosynthesis slows down because the plant doesn’t get enough oxygen

B
Photosynthesis slows down because the reactants are in short supply

C
It has no effect because photosynthesis depends on energy from the Sun

D
Photosynthesis speeds up because glucose is trapped in the plant’s leaves
3
Why does photosynthesis occur during the day?

A
Oxygen levels increase during the night and decrease during the day

B
Carbon dioxide enters stomata during the day, and oxygen leaves during the night

C
Light from the Sun is only available during the day and not at night

D
High temperatures during the day provide energy for photosynthesis
After photosynthesis, plants immediately use some glucose for growth and maintenance. Leftover glucose can be stored for later use in large starch molecules. Glucose is also the primary source of energy for animals, including humans. How do we get our glucose? Well, we eat plants. And we eat animals that eat plants, and animals that eat animals that eat plants. You get the idea!

Even oxygen—a waste product of photosynthesis—supports life on Earth. In fact, photosynthetic organisms have gradually increased the amount of oxygen in our atmosphere over the last 3 billion years. For every wonderful, oxygen-filled breath you take, thank a plant. Without photosynthesis, we wouldn’t be here today!

4
What two things can a plant do with glucose produced from photosynthesis?

Convert glucose to oxygen and release it into the air

Store glucose in starch molecules

Release glucose back into the soil

Release energy from glucose to grow
5
Fill in the blanks to complete the sentence. Not all answer choices will be used.

Plants store some
produced during daylight hours. This allows
to continue at night when
is unavailable.

6
When you eat a sweet potato, digestion releases the chemical energy it stores. What is the original source of this energy?

A
Starch molecules in the plant

B
Water found in the soil

C
Carbon dioxide found in the air

D
Light energy from the Sun

Answer 1

Here are the answers based on your questions:

1. What effect will this have on photosynthesis? B: Photosynthesis slows down because the reactants are in short supply.
   When stomata close, carbon dioxide intake is reduced, which limits the availability of one of the key reactants needed for photosynthesis.

2. Why does photosynthesis occur during the day? C: Light from the Sun is only available during the day and not at night.
   Photosynthesis requires light energy, which is provided by the Sun during the day.

3. What two things can a plant do with glucose produced from photosynthesis?

   • Store glucose in starch molecules
   • Release energy from glucose to grow
     Both actions are essential for the plant's growth and energy management.

4. Fill in the blanks to complete the sentence. Not all answer choices will be used. Plants store some glucose produced during daylight hours. This allows photosynthesis to continue at night when light is unavailable.
   This indicates that plants can store glucose for use when they cannot photosynthesize.

5. What is the original source of chemical energy released when you eat a sweet potato? D: Light energy from the Sun.
   The energy in sweet potatoes comes from sunlight that was converted into chemical energy by the plant during the process of photosynthesis.