Topic 3 - Coordination And Control In Plants Flashcards
What are plant growth substances
Plant responses that are controlled by hormone-like chemical coordinators
What is the apical meristem
The tip of the plant where cell division takes place
What is the zone of elongation
The region below the tip where cells enlarge
What is the internode of a plant
The region between the nodes, or points at which leaves develop
What are the three major plant growth substances
Auxins
Cytokinins
Gibberellins
What is the site of production and main plant growth effect of Auxins
The produce in the growing tip of the stem, and stimulate elongation of cells
What is the site of production and main plant growth effect of Cytokinins
They produce in actively dividing tissues and promote cell division, especially in combination with auxins
What is the site of production and main plant growth effect of Gibberellins
They produce in apical bud and leaves, and stimulate elongation of intermodal regions
What is the process of cell enlargement
The cell of the apical meristem absorbs water by osmosis and form permanent vacuoles. As the vacuoles absorb water, the cell increases in size
What is the process of auxin action
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
When do long-day plants flower
Only if the day length exceeds a critical value
When do short-day plants flower
Only if the day length is less than a critical value
What is photoperiod measured in
Phytochrome pigments
What are the two forms of Phytochrome
P660 and P730
What is the difference in red-light absorption of P660 and P730
P730 maximally absorbs Red light of wavelength 730nm, while P660 maximally absorbs far-red light of wavelength 660nm
What happens to the Phytochrome forms in darkness
There is a slow conversion of P730 to P660, which means P660 accumulates at night
Why does P730 accumulate during the day
Daylight contains more red light than far-red light
What is the physically active form of Phytochrome, and why
P730, because it can either stimulate or inhibit flowering
What is the Phytochrome response in Long Day, and Short Night, and which plant flowers
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
What is the Phytochrome response in Short Day, and Long Night, and which plant flowers
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
What is the Phytochrome response of a Short Day, and Long night interrupted by short light period
During the night, the short light period converts P660 to P730 - enabling sufficient P730 to accumulate, resulting in flowering of Long Day plants
What is the difference in receptors and effectors
Receptors receive the stimulus
Effectors being about the response
What is an example of a receptor in plants, and animals
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
What is an example of an effector in plants and animals
A bud may develop into a flower, while cells elongate in the zone of elongation in response to auxin
In animals, muscles contract
Why do animals need an additional system to linking receptors fast
They can move from one place to another
