5.1.5 - Plants And Animal Responses

Question 1

What is tropism in plants?

Answer 1

Tropism is a directional growth response of a plant as a result of a stimulus.

Question 2

Give 4 examples of types of tropism?

Answer 2

*Thigmotropism (response to touch)
*Geotropism (response to gravity)
*Chemotropism (response to chemicals)
*Phototropism (response to light)

Question 3

What is positive tropism?

Answer 3

The growth towards a stimuli like light

Question 4

What is negative tropism?

Answer 4

The growth away from a stimuli

Question 5

What is a mastic response, and give an example>

Answer 5

A mastic response is a non-directional response to external stimuli.
##Footnote
Mimosa pudica rolls its leaves when touched (a thigmonastic response).

Question 6

What is auxin?

Answer 6

Auxin is a plant growth hormone located in the tips of shoots and roots.

Question 7

What is auxins role in plant growth?

Answer 7

It stimulates cell elongation, causing the plant to bend towards light due to IAA (indoleacetic acid) accumulation on the shaded side.

Question 8

What is apical dominance?

Answer 8

Apical dominance is when a plant favors upward growth from the top (apex) over other parts. Auxin promotes this upward growth.

Question 9

What is lateral growth?

Answer 9

Lateral growth refers to sideward growth of the plant, which is not favored.

Question 10

How is lateral growth affected by auxin?

Answer 10

Auxin inhibits lateral growth and bud growth

Question 11

What role does abscisic acid play in plant growth?

Answer 11

Abscisic acid works along with auxin to inhibit lateral bud growth.

Question 12

What role do cytokinins play in plant growth?

Answer 12

Cytokinins promote lateral bud growth if there is no auxin, allowing the plant to obtain more nutrients.

Question 13

What are gibberellins and what do they promote?

Answer 13

Gibberellins are plant hormones that promote stem elongation and seed germination.

Question 14

Why do small plants have low levels of gibberellins?

Answer 14

Small plants have low levels of gibberellins, which is why they do not grow tall.

Question 15

How do selective weed killers use auxin?

Answer 15

Selective weed killers use high concentrations of synthetic auxin to cause rapid, damaging growth in weeds, making them susceptible to pathogens.
##Footnote
This technique is effective against broadleaf weeds but less harmful to grasses.

Question 16

How is auxin used in rooting powders?

Answer 16

Rooting powders contain auxin at low doses to stimulate root growth in cuttings. The lower ends of cuttings are dipped in powder before planting, which helps roots to develop.

Question 17

How is ethane used to control the ripening of fruit?

Answer 17

Ethene can be used to stimulate the ripening of fruit and is often used for fruits that are delicate and soft when they are ripe and can be easily damaged in transport. Instead the fruit is harvested unripe, transported and then ripened artificially using ethene