Topic 6 - Plant Structures & Their Functions

Question 1

Photosynthetic organisms

Answer 1

• Main producers of food and therefore biomass

Question 2

Balanced equation of Photosynthesis

Answer 2

• 6C02 + 6H2O → C6H12O6 + 6O2

Question 3

Description of Photosynthesis

Answer 3

• Endothermic reaction
• Uses light energy to react with CO2 and water
• Produces glucose and oxygen

Question 4

Explain the effect of temperature on the rate of photosynthesis

Answer 4

• Temperature too high will prevent enzymes from working correctly

Question 5

Explain the effect of light intensity on the rate of photosynthesis

Answer 5

• lower light intensity means less light energy

Question 6

Explain the effect of CO2 concentration on the rate of photosynthesis

Answer 6

• less CO2 means less photosynthesis can occur

Question 7

Inverse square law:

Answer 7

light = 1 / distance^2

Question 8

Core Practical: Investigate the effect of light intensity on rate of photosynthese

Answer 8

1. Place pondweed in solution of NaHCO3, to supply plant with CO2, placed in a boiling water bath
2. Place light source in front of pondweed
3. After 5 mins, measure O2 in plunger
4. Repeat while moving the light source closer

Question 9

Explain how the structure of the root hair cells is adapted to absorb water and mineral ions

Answer 9

• Thin cell walls for osmosis
• Large vacuole for osmosis
• Lots of mitochondria to absorb mineral ions easier
• Long root hairs to increase surface area, so more water can be absorbed

Question 10

Xylem Function:

Answer 10

• Transport water and dissolve minerals from the roots

Question 11

Xylem Structure:

Answer 11

• Broken cell walls between cells
• Contains only a continuous column of water
• Walls thicken due to lignin

Question 12

Phloem Function:

Answer 12

• Transport sucrose and amino acids

Question 13

Phloem Structure:

Answer 13

• Reduced cell contents linked by sieve plates, allowing easy movements of sucrose and amino acids
• Companion cells contain mitochondria to actively transport molecules

Question 14

How are water and mineral ions transported through the xylem

Answer 14

• Transpiration

Question 15

Stomata Structure

Answer 15

• Have tiny opening for water to escape
• Can open and close to regulate the amount of water can escape

Question 16

Transpiration steam

Answer 16

• As water evaporates from leaves, it creates a pull, drawing more water up from the roots.

Question 17

How is sucrose ‘form of glucose’ transported around the plant by translocation?

Answer 17

• Photosynthesis creates sugar
• Sugar is moved into phloem.
• Buildup of sugar causes pressure
• Causes sugar to be pushed into location where it is needed

Question 18

Explain how the structure of a leaf is adapted for photosynthesis and gas exchange

Answer 18

• Thin and Flat shape for surface area
• Transparent epidermis to allow light to penetrate
• Stomata controls movement of gases in and out of the leaf

Question 19

Explain the effect of environmental factors on the rate of water uptake by a plant

Answer 19

• Light intensity affects water uptake
• Air movement affects water uptake
• Temperature causes plant to need more water

Question 20

Equation for Rate of Transpiration

Answer 20

• Rate of Transpiration = Time Interval/Amount of Water Lost

Question 21

Explain how plants are adapted to survive in extreme environments

Answer 21

• Smaller leaf sizes allow extra water retention
• Thicker Cuticle (waxy coating) allows extra water retention
• Stomata may open and close at specific times to reduce water loss.

Question 22

Phototropisms:

Answer 22

• Plant bends toward light source over time

Question 23

Gravitropisms:

Answer 23

• Plant bending due to gravity

Question 24

Commercial uses of auxins:

Answer 24

• Weedkillers
• Rooting powders

Question 25

Commercial uses of gibberellins:

Answer 25

• Germination (turning into plant quicker)
• Fruit and flower formation
• Seedless fruits

Question 26

Commercial use of ethene:

Answer 26

• Fruit ripening