Plant Responses

Question 0

Tropism

Answer 0

A change in the growth of a plant in response to an external stimulus

Question 1

Define stimulus

Answer 1

Anything that causes a reaction in an organism or in any parts of it

Question 2

Positive tropism

Answer 2

When the growth is towards the stimulus

Question 3

Negative tropism

Answer 3

When the growth is away from the stimulus

Question 4

Phototropism

Answer 4

The change in the growth of a plant in response to light.

Increased photosynthesis when leaves are held up to more light

Question 5

Geotropism

Answer 5

Change in growth of a plant in response to gravity

Roots grow down into soil for water and minerals

Question 6

Thigmotropism

Answer 6

Change in growth of a plant in response to touch

Stem and tindrels of ivy wrap around objects to keep leaves upright

Question 7

Hydrotropism

Answer 7

Change in growth of a plant in response to water

Roots grow towards water in the soil

Question 8

Chemo tropism

Answer 8

Change in growth of a plant in response to chemicals

Roots grow towards minerals

Question 9

What is a growth regulator

Answer 9

A chemical that controls the growth of a plant

Question 10

Where are growth regulators made?

Answer 10

In the meristematic regions of a plant. I.e the shoot and root tips and the tips of side shoots

Question 11

Where are growth regulators transported in?

Answer 11

The xylem and phloem

Question 12

Similarity with growth regulators to hormones

Answer 12

Chemical in nature

Action is long lasting

Question 13

Growth promotor example

Answer 13

Auxins , IAA

Question 14

Growth inhibitor example

Answer 14

Ethene

Question 15

Auxins

Transported in the…

Answer 15

Phloem

Question 16

Where does auxin exactly promote growth?

Answer 16

Just behind the shoot and root tip, in the zone of elongation

Question 17

Effects of auxins

Answer 17

Cause cell elongation and growth or bending in phototropism and geotropism

Question 18

Describe auxins role in apical dominance

Answer 18

Auxin is produced in the apex of a plant and moves down the plant and inhibits growth in the lateral side shoots

This means the tip of the plant will grow but not the sides. ( think of a cyprus tree )

Gardeners prune the tips of plants to allow the side shoots to develop and grow a bushier full plant

Question 19

Auxins role in fruit formation

Answer 19

IAA is made in developing seeds which stimulates the formation of fruit around the seeds ( help with protection, animal dispersal)

Question 20

Auxin role in root growth

Answer 20

IAA at LOW concentrations causes roots to grow

Roots grow down LOW therefore LOW conc IAA

Question 21

Auxins role in phototropism

Answer 21

Auxin loosens cell walls and allows them to expand which allows growth and tropisms

In a plant;

If the shoot is exposed to light from one side, auxin will diffuse down the shaded side

The higher concentration of auxin in the shaded side allows the cells to elongate more than unshaded cells on the bright side

As a result of the uneven elongation, the stem bends towards the light.

Question 22

Growth inhibitors

Ethene - what is it and where is it made?

Answer 22

A gas

Made in stem nodes, ripe fruits and decaying leaves

Question 23

Ethenes role

Answer 23

Plays a major role in ripening fruits, stimulating leaves to fall in autumn and ageing plants

Ethene is used commercially to ripen bananas

Question 24

What is an adverse external environment ?

Answer 24

Surroundings that are harmful to an organism

Question 25

Give 3 example of an anatomical protective feature of a plant

Answer 25

Cacti have sharp spines to protect against grazing animals

Nettle leaves have sharp hairs with a stinging poison

Plants are enclosed by a physical barrier consisting of epidermis , bark or a thick cuticle which prevents the entry of pathogens and reduces water loss.

Question 26

3 examples of chemical protective features of plants

Answer 26

Oak trees produce tannins in their leaves to protect them against caterpillars

Rhubarb leaves contain oxalic acid which has a bitter taste

Plants contain heat-shock proteins which surround other proteins such as enzymes and help them maintain their shape