4. Understand the importance of photosynthesis, respiration, the movement of water and minerals through the plant.

Question 1

4. 1.1 State the equation for photosynthesis in words and state the necessity for chlorophyll and light.
5. 1.2 List the environmental factors that affect the rate of photosynthesis:
6. 1.3 Describe how these factors affect the rate of photosynthesis: to include Law of Limiting Factors and how growers can optimise the conditions for photosynthesis

Answer 1

4. 1.1 Carbon dioxide + water + energy from sunlight absorbed by chlorophyll —-> sugar + oxygen
5. 1.2 temperature, light (intensity, quality/PAR and duration), carbon dioxide, water and mineral nutrients.
6. 1.3 light, co2, water, warmth and chlorophyll must all be in pentiful supply to maximise the rate of photosynthesis. A shortage will reduce the rate. Whichever is in short supply is the LIMITING FACTOR

Question 2

4. 2.1 State the equations for aerobic and anaerobic respiration in words:
5. 2.2 List the factors that affect the rate of respiration:
6. 2.3 Describe how these factors affect the rate of aerobic respiration.
7. 2.4 Describe the significance of anaerobic and aerobic respiration in horticultural situations: waterlogging, propagation, produce storage, seed storage.

Answer 2

4.2.1

AEROBIC

the complete breakdown of sugars in the presence of oxygen to release a high yield of energy, carbon dioxide and water

sugars + oxygen—> water+ carbon dioxide>>> high yield of energy

ANAEROBIC

partial breakdown of sugars when oxygen is absent to release a low yield of energy, carbon dioxide and ethanol (alcohol).

sugars—–> ethanol+ carbon dioxide>>>>> low yield of energy.

4.2.2 Factors Affecting aerobic respiration rate

oxygen and temperature

4.2.3 How these factors affect the rate of aerobic respiration

Respiration is highest in actively growing cells when a seed germinates or when a cutting is producing new roots

Lowest when the seed is dormant or when the plant is inactive during winter

4.2.4 Horticultural Situations

By reducing the rate of respiration in stored crops, fruit, seeds and bulbs will keep fresh for longer. Storage facilities reduce temperatures and may also replace ambient oxygen with inert gases such as nitrogen to limit the rate of respiration.

Question 3

4. 3.1 Distinguish between diffusion and osmosis to include: gaseous and liquid diffusion, transportation, and water uptake. Identify examples of diffusion in plants, to include: transpiration and gaseous exchange.
5. 3.2 Identify examples of osmosis in plants,
6. 3.3 Describe the pathway of water movement from the soil through the plant into the atmosphere
7. 3.4 State what is meant by the term ‘transpiration’.
8. 3.5 List the factors that affect the rate of transpiration:
9. 3.6 Describe how the plant may limit water loss, to include: stomatal closure and leaf adaptations (hairs, thick cuticle, needles). ONE named plant example should be known for EACH adaptation.
10. 3.7 Describe Plant Mineral Nutrient Uptake

Answer 3

4.3.1

Osmosis - movement of water from area of low salt concentration to higher salt concentration

Diffusion - movement of gas/liquid from area of higher concentration to lower concentration

4.3.2

1. water uptake into cells,
2. turgor
3. cell expansion.

4.3.3

1. pathway across the root
2. transport through xylem of stem (transpiration pull):
3. pathway across leaf, (xylem in veins, osmosis across leaf cells,
4. flow through leaf cell walls,
5. evaporation from leaf cell walls into mesophyll spaces);
6. diffusion through stomata of leaf
7. 3.4 Transpiration –> diffusion of water molecules from the leaf to the air
8. 3.5 relative humidity, temperature, wind speed
9. 3.6
10. Hairy leaves - Stachys byzantia
11. Thick cuticle - Ilex aquifolium
12. Needles - Opuntia polycantha

4.3.7 Absorption is by minerals in soluble form in the water in the soil, and are absorbed through the root hairs

ACTIVE TRANSPORT

Uses energy from repspiration to move minerals across the root hair membranes into the plant. Then the solutions are moved around the plant in the xylem and the phloem

Question 4

4.4.1 Describe how the internal and external structure of the leaf is designed to maximise photosynthesis and minimise transpiration.

Answer 4

4.4.1

Stomata - tiny pores on the lower epidermis of leaves

Stoma - 2 guard cells that surround the stomatal structure . Guard cells open and close the stomatal aperture. Cells take up water and expand unevenly and the thickened walls are pulled apart to form an aperture

When cells lose water, they become flaccid and the aperture closes , as the plant loses turgidity.

Stomata are open in day, closed at night