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Flashcards in Plant Responses Deck (20)
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1
Q

Name a plant growth regulator that promotes growth and give a precise location for a site of action.

A

IAA
Causes root and shoot growth.
acts just behind the growing tip of the root or shoot.

2
Q

Through which part of a stem are growth promoters transported?

A

Mostly transported in vascular bundles, in either the xylen or phloem

3
Q

Outline two uses of growth promoters in horticulture.

A

1) Rooting powders are used to encourage stem cuttings to produce roots
2) ethene to ripen bananas

4
Q

Give an example of growth regulator that inhibits growth.

A

Abscisic acid causes stomata to close and the production of bud scales in reaction to stress.

5
Q

What do you understand by the term adverse external environment?

A

Means the area where the organism lives is not well-suited to it or harsh on it.

6
Q

Give two ways in which plants protect themselves from adverse external environments.

A

1) By closing stomata to prevent water loss during periods of water shortage
2) By developing a thick outer coat or bark to protect themselves
3) plants produce heat shock proteins that bind to proteins and help prevent them from denaturing if the temperature rises too much.

7
Q

Name the group of substances in plants which control responses to external stimuli.

A

Growth regulators

8
Q

What name is given to the regions in plants in which growth regulators are produced?

A

Meristematic regions

9
Q

Give locations for two of meristematic regions.

A

Root and shoot tip

10
Q

Most plant shoots are positively phototropic. Explain the term PHOTOTROPIC.

A

Plant shoots grow towards the light. Phototropic is the growth response of a plant to light, when it’s positive, it means the plant grows towards it.

11
Q

How do plants benefit from being positively phototropic?

A

The plant gets more light which speeds up photosynthesis.

12
Q

Explain the mechanism of response by a plant to named external stimulus.

A

External stimulus:
Light auxins are growth regulators, which work by loosening cell walls and allowing cells to expand.
Auxins are produced by the shoot tips of plants.
If a plant stem is exposed to light from one side, the auxin IAA will diffuse down the other side and cause the cells to elongate on the shady side. As a result the stem will bend over towards the light.

13
Q

What is a tropism?

A

A tropism is the growth response of a plant to a stimulus.

14
Q

What is a plant growth regulator?

A

Is a chemical produced in small amounts that controls (stimulates or inhibits) the growth of a plant.

15
Q

Give an example of a regulator in plants that inhibits growth.

A

IAA / ethene

16
Q

Give two uses of plant growth regulators in horticulture.

A

1) ethene ripens bananas

2) tissue culturing

17
Q

Distinguish between thigmotropism and chemotropism.

A

Thigmotropism is the plant’s response to touch, while chemotropism is the plant’s response to chemicals.

18
Q

What is an auxin?

A

plant growth regulator

19
Q

Give two examples of uses of synthetic (man-made) auxins.

A

1) Can be used to encourage cuttings

2) to develop roots, i.e. rooting powder

20
Q

State two ways in which growth regulators in plants are similar to hormones in animals.

A

1) produced in small amounts, can have positive or negative effect
2) travel from where they are produced to area where they cause effect