Topic 3 - Coordination And Control In Plants Flashcards

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1
Q

What are plant growth substances

A

Plant responses that are controlled by hormone-like chemical coordinators

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2
Q

What is the apical meristem

A

The tip of the plant where cell division takes place

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3
Q

What is the zone of elongation

A

The region below the tip where cells enlarge

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4
Q

What is the internode of a plant

A

The region between the nodes, or points at which leaves develop

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5
Q

What are the three major plant growth substances

A

Auxins
Cytokinins
Gibberellins

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6
Q

What is the site of production and main plant growth effect of Auxins

A

The produce in the growing tip of the stem, and stimulate elongation of cells

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7
Q

What is the site of production and main plant growth effect of Cytokinins

A

They produce in actively dividing tissues and promote cell division, especially in combination with auxins

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8
Q

What is the site of production and main plant growth effect of Gibberellins

A

They produce in apical bud and leaves, and stimulate elongation of intermodal regions

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9
Q

What is the process of cell enlargement

A

The cell of the apical meristem absorbs water by osmosis and form permanent vacuoles. As the vacuoles absorb water, the cell increases in size

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10
Q

What is the process of auxin action

A

They are produced in the apical meristem
They diffuse down the shoot towards the zone of elongation
They bind to specific receptors on the membrane of new cells, which causes the membranes pumps to move H ions out into the cell wall
This acidification activates agents which loosen linkages between cellulose microfibrils allowing slippage
The cells absorb water by osmosis and expand the cell
The more auxin that is received, the more the cell can expand

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11
Q

When do long-day plants flower

A

Only if the day length exceeds a critical value

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12
Q

When do short-day plants flower

A

Only if the day length is less than a critical value

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13
Q

What is photoperiod measured in

A

Phytochrome pigments

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14
Q

What are the two forms of Phytochrome

A

P660 and P730

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15
Q

What is the difference in red-light absorption of P660 and P730

A

P730 maximally absorbs Red light of wavelength 730nm, while P660 maximally absorbs far-red light of wavelength 660nm

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16
Q

What happens to the Phytochrome forms in darkness

A

There is a slow conversion of P730 to P660, which means P660 accumulates at night

17
Q

Why does P730 accumulate during the day

A

Daylight contains more red light than far-red light

18
Q

What is the physically active form of Phytochrome, and why

A

P730, because it can either stimulate or inhibit flowering

19
Q

What is the Phytochrome response in Long Day, and Short Night, and which plant flowers

A

P730 accumulates during the long day and is not sufficiently removed during the short night- mostly P730, which results in flowering of Long Day plants

20
Q

What is the Phytochrome response in Short Day, and Long Night, and which plant flowers

A

P730 is removed during the long night and is not produced sufficiently during the short day - little P730, resulting in flowering of Short Day Plants

21
Q

What is the Phytochrome response of a Short Day, and Long night interrupted by short light period

A

During the night, the short light period converts P660 to P730 - enabling sufficient P730 to accumulate, resulting in flowering of Long Day plants

22
Q

What is the difference in receptors and effectors

A

Receptors receive the stimulus
Effectors being about the response

23
Q

What is an example of a receptor in plants, and animals

A

The Phytochrome system in the leaf detects the photoperiod
The osmoreceptors in the hypothalamus are stimulated by changes in the water potential of the blood

24
Q

What is an example of an effector in plants and animals

A

A bud may develop into a flower, while cells elongate in the zone of elongation in response to auxin
In animals, muscles contract

25
Q

Why do animals need an additional system to linking receptors fast

A

They can move from one place to another