Nutrition in plants

Question 1

What is the word equation for photosynthesis?

Answer 1

Carbon dioxide + water → glucose + oxygen.

Question 2

What is the balanced chemical equation for photosynthesis?

Answer 2

6CO₂ + 6H₂O → (light) C₆H₁₂O₆ + 6O₂.

Question 3

What adaptations help the leaf with photosynthesis?

Answer 3

• The leaf is thin, leading to a shorter diffusion distance for quicker diffusion.
• The leaf is thin, allowing light to easily penetrate through.
• Leaves in the shade have more chloroplasts and a darker color to absorb more light.

Question 4

What is the function of the waxy cuticle?

Answer 4

It reduces water loss from the leaf.

Question 5

What is the function of the upper epidermis?

Answer 5

It is thin and transparent to allow light to pass through.

Question 6

How is the palisade mesophyll adapted for photosynthesis?

Answer 6

1. Contains a large number of chloroplasts for photosynthesis.
2. Tightly packed and close to the upper epidermis for maximum light absorption.

Question 7

How is the spongy mesophyll adapted for gas exchange?

Answer 7

1. Loosely packed with air gaps to increase surface area for rapid diffusion of gases.
2. Has a layer of moisture to dissolve gases.

Question 8

What is the function of the lower epidermis?

Answer 8

1. Contains stomata through which gases diffuse in and out.
2. Has guard cells that control the opening and closing of stomata.

Question 9

How does light intensity affect the rate of photosynthesis?

Answer 9

As light intensity increases, the rate of photosynthesis increases.

Question 10

How does CO₂ concentration affect the rate of photosynthesis?

Answer 10

As CO₂ concentration increases, the rate of photosynthesis increases.

Question 11

How does temperature affect the rate of photosynthesis?

Answer 11

• As temperature increases, the rate of photosynthesis increases because particles gain kinetic energy and collide more.
• At very high temperatures, the rate decreases because enzymes denature, and stomata close to prevent water loss, stopping CO₂ from entering the leaf.

Question 12

What is the function of nitrates in plants?

Answer 12

Nitrates are needed to make amino acids, which build proteins.

Question 13

What is the function of magnesium in plants?

Answer 13

Magnesium is needed to make chlorophyll, which absorbs light for photosynthesis.

Question 14

How does light intensity affect the rate of photosynthesis?

Answer 14

The closer the light source, the higher the rate of photosynthesis, as more stomata remain open, allowing more CO₂ to enter.

Question 15

How does temperature affect the rate of photosynthesis in an experiment?

Answer 15

• Higher temperature increases the kinetic energy of gas particles, increasing the rate of diffusion and photosynthesis.
• At very high temperatures, stomata close to reduce water loss, stopping CO₂ from entering and stopping photosynthesis.

Question 16

How can CO₂ concentration be manipulated in an experiment?

Answer 16

By adding different concentrations of potassium hydrogen carbonate (KHCO₃).

Question 17

Why is a plant kept in a dark room for 24 hours before testing for starch?

Answer 17

To destarch the plant, ensuring only respiration occurs and no photosynthesis.

Question 18

• How is starch tested in a leaf?
• What are the possible results of the starch test?

Answer 18

1. Cover part of the leaf with black paper and expose the plant to light.
2. Boil the leaf in water to denature enzymes.
3. Boil the leaf in ethanol in a water bath to remove chlorophyll.
4. Soften the leaf in cold water.
5. Add iodine solution.

Possible results:
* Positive (+ve): Blue-black (starch present).
* Negative (-ve): Brown (no starch present).