Mod 5 - Plant Responses

Question 1

Roles of cytokinins (4)

Answer 1

Promote cell division
Delay leaf senescence
Overcome apical dominance
Promote cell expansion

Question 2

Role of Abscisic acid (3)

Answer 2

Inhibits seed germination and growth

Causes stomata closure when the plant is stressed by low water availability

Question 3

Role of auxins and give an example of a type of auxin (3+1)

Answer 3

E.g. IAA (indole-3-acetic acid)
Promote cell elongation
Inhibit growth of side shoots
Inhibit lead abscission (leaf fall)

Question 4

Role of gibberellins (2)

Answer 4

Promote seed germination

Promote growth of stems

Question 5

Effect of ethane (1)

Answer 5

Promotes fruit ripening

Question 6

How do hormones move around in the plant? (3)

Answer 6

Active transport
Diffusion
Mass flow in the phloem sap or in xylem vessels

Question 7

What do plants respond to? (3)

Answer 7

Biotic
Abiotic components of environment
External stimuli

Question 8

What types of stimuli may plants respond to?

Answer 8

Change in temperature
Windy conditions
Threat of herbivores

Question 9

How do plants respond to higher temperatures?

Answer 9

Plants may deposit thicker layers of wax on their leaves

Question 10

How do plants respond to windy conditions?

Answer 10

They may have vascular tissue which is more lignified

Question 11

What are tannins? (3)

Answer 11

Tannins are toxic to microorganisms and larger herbivores.
In leaves, they are found in the upper epidermis, and make the leaf taste bad. In roots, they prevent infiltration by pathogenic microorganisms.

Question 12

What are alkaloids? (3)

Where are they found?

Answer 12

They are derived from amino acids.
In plants, scientists think they are a feeding deterrent to animals, tasting bitter.
They are located in growing tips and flowers, and peripheral cell layers of stems and roots.

Question 13

What are pheromones?

Answer 13

Chemicals which are released by one individual and which can effect the behaviour or physiology of another.

Question 14

What is phototropism and why is it beneficial?

Answer 14

Shoots grow towards light (positively phototropic) which enables them to photosynthesise

Question 15

What is geotropism and why is it beneficial?

Answer 15

Roots grow towards the pull of gravity.
This anchors them in the soil and helps them to take up water for support (to keep cells turgid), as raw materials for photosynthesis and to help cool the plant.
There will also be minerals, such as nitrate in the water needed for the synthesis of amino acids