Chapter 6 - Plant nutrition

Question 1

What is photosynthesis?

Answer 1

It is a metabolic reaction occurring in plants in which light energy converts raw materials into carbohydrates such as glucose which can be stored and used as an energy resource via respiration

Question 2

Where does photosynthesis occur?

Answer 2

It takes place in chloroplasts of plant cells, Chloroplasts contain chlorophyll that transfers light energy into chemical energy.

Question 3

Write down the word equation and symbol equation for photosynthesis:

Answer 3

Carbon dioxide + water —-> glucose +oxygen

6CO2 + 6H2O —-> C6H12O6 + 6O2

Question 4

List the factors that affect the rate of photosynthesis and how it affects it:

Answer 4

Carbon dioxide concentration - As CO2 concentration increases rate of photosynthesis increases
Temperature - Photosynthesis requires enzymes to carry reaction, Enzymes have an optimum temperature usually 25 C
Light intensity - As light intensity increases rate of photosynthesis increases sometimes it may heat plant which could make that the limiting factor

Question 5

What is a limiting factor?

Answer 5

It is the factor that is least available. For example in photosynthesis if the CO2 is less but the other factors in great supply the CO2 is the limiting factor meaning less photosynthesis occurs.

Question 6

Plant leaves must be adapted to allow photosynthesis to occur. This means limiting water loss, absorbing as much light and allowing for efficient gas exchange, Explain the adaptations of the plant leave:

Answer 6

• Chloroplasts: At top of leaf to maximise light absorbed, have chlorophyll which allows light energy to be absorbed and converted into chemical energy
• cuticle: Waxy layer surrounding leaf. Provides waterproofing and reduces water loss
• Guard cells and stomata: stomata located underneath and allow CO2 in via diffusion, and water vapor and oxygen out. Guard cells close and open stomata to limit water loss. Guard cells close when limited water supply.
• Upper and lower epidermis: acts as a protective barrier around leaf to prevent pathogens entering. Transparent
• Palisade mesophyll: Near top of leaf where most light therefore adapted to absorb light efficiently. Contains chloroplasts. Gaps between cells to allow gas exchange and Osmosis
• Spongy mesophyll: Lower layer of leaf, Cells loosely placed and have large surface area to allow rapid diffusion
• Vascular bundles: plants transport system. Xylem and phloem
• Xylem: Used to transport water from roots in transpiration, made of dead hollowed cells with ends removed to make tube for water to pass through. Thick cell wall for strength.
• Phloem: Made of living cells used to transport sugars and food. Have no nucleus

Question 7

Study the diagram on page 60 fig 6.3

Answer 7

Test self with fig 6.3

Question 8

What is the use of nitrate ions in plants?

Answer 8

Used to build amino acids, thus proteins and enzymes.

Question 9

What is the use of magnesium ions in plants?

Answer 9

Used to make chlorophyll.

Question 10

What happens if a plant doesn’t have enough nitrate ions?

Answer 10

Plant would not be able to grow or repair itself. Leads to yellow leaves and poor growth.

Question 11

What happens if a plant doesn’t have enough magnesium ions?

Answer 11

Leads to lack of chlorophyll, photosynthesis doesn’t occur. Sugars cannot be formed, plant doesn’t have enough energy to grow and repair itself.