Topic 6 - Plant Structures and Their Functions

Question 1

How do plants generate food?

Answer 1

Via photosynthesis

Question 2

Is photosynthesis an exothermic or endothermic reaction?

Answer 2

Endothermic, as it takes in energy (heat energy from the sun)

Question 3

In what plant structure does photosynthesis happen?

Answer 3

Chloroplasts

Question 4

What is the balanced symbol equation for photosynthesis?

Answer 4

6CO2 + 6H2O + Light Energy + Chlorophyll = C6H12O6 + 6O2

Question 5

Describe a method to test the effect of light intensity on the rate of photosynthesis:

Answer 5

• Put pondweed in a beaker with water and sodium hydrogencarbonate
• Connect gas syringe to the top of beaker through a cork
• Set a light source at a set distance away
• Measure the distance moved by the gas syringe due to oxygen bubbles
• Repeat for different distances
• Plot a graph for the results

Question 6

What are the three limiting factors for photosynthesis?

Answer 6

• Light Intensity
• Carbon Dioxide
• Temperature

Question 7

What is the inverse square law?

Answer 7

As the distance increases, the light intensity decreases by a factor of x squared

Question 8

Describe the three graphs for limiting factors of photosynthesis:

Answer 8

• Light Intensity: Linear, then flat
• Carbon Dioxide: Linear, then flat
• Temperature: A curve around 37°C

Question 9

How does light intensity affect the rate of photosynthesis?

Answer 9

It is needed for photosynthesis, so if it is lower, then the rate will be slower

Question 10

How does carbon dioxide affect the rate of photosynthesis?

Answer 10

It is a reactant of photosynthesis, so if it is lower, then the rate will be slower

Question 11

How does temperature affect the rate of photosynthesis?

Answer 11

At low temperatures, the enzymes do not have the activation energy, but at high temperatures, they become denatured

Question 12

What do root hairs do?

Answer 12

Take in minerals and water, generally by active transport

Question 13

What do phloem tubes transport?

Answer 13

Food

Question 14

What do xylem tubes transport?

Answer 14

Water (UP)

Question 15

What is transpiration?

Answer 15

The loss of water from a plant

Question 16

What causes transpiration to happen?

Answer 16

Evaporation and diffusion

Question 17

What are stomata needed for?

Answer 17

Gas exchange

Question 18

How do guard cells affect whether stomata are open or closed?

Answer 18

If the guard cells are turgid, the stoma is open

If the guard cells are flaccid, the stoma is closed

Question 19

What environmental factors affect transpiration rate?

Answer 19

• Light Intensity
• Temperature
• Air Flow

Question 20

Give examples of how leaves are adapted for photosynthesis and gas exchange:

Answer 20

• Leaves are broad
• Palisade layer has lots of chloroplasts
• Waxy Cuticle
• Upper epidermis is transparent to allow light through
• Air spaces above the stomata

Question 21

What are auxins?

Answer 21

Plant growth hormones that control growth at the tips of shoots and roots

Question 22

Finish the sentence: Shoots are positively ___ and negatively ___

Answer 22

Phototropic

Gravitropic

Question 23

Finish the sentence: Roots are positively ___ and negatively ___

Answer 23

Gravitropic

Phototropic

Question 24

What are commercial uses of plant hormones?

Answer 24

• Selective weedkillers
• Growing from cuttings
• Controlling ripening
• Controlling flowering
• Producing seedless fruit
• Controlling seed germination

Question 25

What is the plant hormone that controls ripening?

Answer 25

Ethene, as it causes the fruit to ripen

Question 26

Why do stores use ethene for their produce?

Answer 26

Because it ensures that the fruit becomes ripe whilst on the shelves, and ensures that they can sell that fruit all year round, depsite it only being grown for 2 months a year!