Chpter 19 - Coordination In Plants Flashcards
1
Q
Define tropic responses
A
- growth movements made by part of the plant in response to stimuli
- response toward stimulus-positive
- response away from stimulus - negative
2
Q
What is Phototropism
A
- growth response of part of the plant to light
- shoots, stem and leaves grow upwards - positive phototropism
- radicles grow away from sun - negative phototropism
3
Q
Role of auxins
A
- Auxins are produced in the tips
- moves by diffusion
- auxins collect and accumulate in shaded area
- the cells on the shaded side will grow and elongate
- this causes differential growth
- shaded side grows faster
- NB auxins stimulate growth in stems
4
Q
Advantages of phototropism
A
- growing towards light enables maximum absorption of light
- flowers better exposed for pollination
5
Q
Geotropism in plants
A
- geotropism is the growth response to the stimulus gravity
- radicles and roots grow downwards - positive geotropism
- shoots grow away from gravity - negative geotropism
6
Q
Role of auxins in geotropism
A
- produced near the tip of the root
- moves by diffusion
- moves to the lower side of the root
- slows down cell growth
- results in differential growth
- NB auxins inhibit growth in roots
7
Q
Advantages of geotropism
A
- to obtain water and minerals
- for anchorage and stability
8
Q
Name the apparatus used to experiment geotropism
A
- clinostat
9
Q
Describe the effect of auxins used as weed killers
A
- weed killers contain auxins or 2.4 D
- in high concentrations it kills dicots but have no effect on monocots
- dicots grow rapidly and die
- some are selective and used to control weeds in grass lawns
10
Q
Describe the effect of auxins in production of seedless fruit
A
- synthetic gibberellic acid is applied to unpollinated flowers fruit begin to develop without prior fertilisation
- fruit looks similar but are seedless
- this is called parthenocarpy
11
Q
Effects of auxins in ripening of fruit
A
- ethene is released from ripe fruit
- ethene stimulates ripening of other fruit
- fruit growers use ethene when transporting picked fruit
12
Q
Effect of auxins in the rooting of cuttings
A
- auxins and cytokinins accelerate root formation in cuttings
- it’s an ingredient of rooting powder
- when applied it encourages roots to develop
- it stimulates cell division and determines cell differentiation
13
Q
Effects of auxins in micro propagation
A
- is done by taking a sample of cells in growing tip of root or stem
- cells are separated by special techniques
- auxins are added to stimulate mitosis
14
Q
Other uses of auxins
A
- prevent potatoes from sprouting
- can slow down ripening of grapefruit
- stimulate cherry and peach
- can delay leaf fall
- promote flowering in pineapples
15
Q
Plant growth regulators
A
- a chemical substance that effects activities of cells and organs in plants
