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Flashcards in Plant Responses Deck (18):
0

Gibberellin (commercially)

- promotes growth = larger+ sweeter grapes
- cause some citrus fruits to stay on the plant longer = bigger fruits
- longer stems = more sugar in sugar canes
- in beer stimulates barley grains to germinate = the fermentation of alcohol

1

Ethene (commercially)

- promotes ripening
- pick unripe food & exported - ethene added at destination to ripen

2

Auxins (commercially)

- prevents abscission - allowed to ripen
- seedless fruits
- stimulate root growth - vegetative propagation
- synthetic versions can be used as selective herbicides - kill broad leaved plants not grass like crops

3

Leaf abscission (why?)

- leaves lost in winter
- reduce water loss
- prevent frost damage & fungal infections
- as not photosynthesising

4

Leaf abscission (how?)

- drop in auxin production
- increased sensitivity to ethene
- increased production of ethene
- abscission layer at base of stalk grows
- layer hydrolyses and breaks off at the petiole
- another protective layer is formed

5

Gibberellin

- can cause rapid growth of stems
- causes stems to get longer at the internodes
- dwarf varieties dont have the gene for GA - good more energy for seeds/crop less growth

6

Internode

- lengths of stem between leaf stalks

7

Evidence auxin concentration stops growth of side shoots

- if you cut the tips off 2 shoots & apply IAA to 1 - that 1 will show apical dominance
- the other side shoots will grow
- if plant is upside down - side shoots grow

8

Evidence for apical dominance

- cut off the tip = growth of lateral buds as no apex

9

Apical dominance

- the inhibition of the growth of lateral buds by the presence of an active apical meristem

10

Phototropism (stages)

- phototropins become phosphorylated from light = sideways gradient
- sideways movement of auxin
- more auxin on shady side
- more auxin = more cell elongation
- grows towards the light

11

How does auxin cause cell elongation

- build up of h+ ions
- activates an enzyme that breaks down the cell wall
- water enters by osmosis
- as shown in phototropism

12

Apical meristem

- the region near the tip of a plant shoot where cells are constantly dividing

13

Phototropins

- acts as a receptor for blue light
- are phosphorylated by blue light
- cause a gradient for phototropism

14

Geotropism

- directional growth response to gravity

15

Phototropism

Directional growth in response to light

16

Tropisms

- a directional growth response in response to a stimuli

17

Nastic movements

- a relatively rapid response of a plant to a stimulus - no direction
-ie petals closing down
- normally from changes in the turgor of specialised cells
- ie venus fly trap