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Biology > Chapter 16 -plant hormones > Flashcards

Chapter 16 -plant hormones Flashcards

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1
Q

Ways hormones alter plant’s growth in response to overcrowding?

A

Auxin:

  • plants will grow taller + will climb up over the other plants
  • roots will grow towards water + minerals
  • phototropism will cause shoots to bend towards the light
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2
Q

How hormones alter growth if top of plant shoot eaten by animal?

A
  • less auxin
  • apical dominance stopped
  • lateral buds develop
  • side shoots grow
  • plant becomes bushy
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3
Q

Mechanism of phototropism?

A
  • apical shoot produces auxin
  • unilateral light causes lateral movement of auxin to shaded side from lit side
  • greater auxin conc on shaded side
  • auxin causes cell wall loosening + thus cell elongation
  • bc H+pumped into cell wall
  • low pH allows enzymes to work
  • binds broken within cellulose in wall
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4
Q

Similarities in action of plant + animal hormones in cell signalling?

A
  • hormone binds to receptor

- may involve switching genes on + off

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5
Q

Why plants are more able to form natural reproductive clones through asexual reproduction than animals?

A
  • plant cells are totipotent
  • retain ability to differentiate though its whole life
  • most animal cells not totipotent
  • meristematic tissue in plants contain totipotent cells
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6
Q

Tropism?

A

Directional growth response of a plant

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7
Q

Signalling molecule that enables plants to respond to environmental change?

A

Hormones

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8
Q

Plants that lose their leaves seasonally?

A

Deciduous

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9
Q

Why plants need to be able to respond to their environment?

A
  • protect themselves against herbivory
  • avoid abiotic stress
  • maximise photosynthesis
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10
Q

Why all lettuce seeds keeps at 25c during experiment testing hormones?

A
  • fair test
  • so temp doesn’t affect results
  • temp affects enzyme activity
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11
Q

Commercial uses?

A
  • selective weed killer
  • rooting powder
  • controls ripening
  • controls fruit dropping
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12
Q

Insecticide absorbed by roots + leaves. How transported to fruits?

A
  • in phloem by translocation

- in xylem by transpiration

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13
Q

Why controls are necessary?

A

-show response without treatment

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14
Q

Why both plants + animals need to be able to respond to changes in their environment?

A
  • counter abiotic stress
  • avoid being eaten
  • access resources
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15
Q

What type of tropism do shoots show?

A
  • positive phototropism

- negative geotropism

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16
Q

Why type of tropism do roots show?

A
  • negative phototropism

- positive geotropism

17
Q

How is IAA transported?

A

In the phloem

18
Q

Apical dominance?

A

vertical growth is dominant over lateral growth

19
Q

How to control conc of CO2?

A

Burn paraffin

20
Q

How to control temp in greenhouse?

A

Use heaters

21
Q

How to control light in greenhouse?

A

Use glass windows

22
Q

How this result can be identified as an anomaly?

A

Repeat test

23
Q

Do sieve tube elements contain chloroplasts?

A

Yes

24
Q

Limiting factor?

A

The factor that will determine the rate when at low level

25
Q

Why plant leaf described as organ?

A
  • similar plant cells form a tissue. Tissue carries out specific function
  • diff tissues form an organ. Organ carries out specific function.
26
Q

Role of IAA?

A

Cell elongation

27
Q

How auxin causes cell elongation?

A
  • auxin molecules bind to specific receptor sites in plant cell membrane Activating process which pumps H+ ions into cell wall spaces, lowering pH to 5
  • this is the optimum pH for the enzymes that break down bonds between cellulose microfibrils, so they slide past each other easily
  • walls remain flexible allowing cells to stretch and grow
28
Q

Why do trees lose their leaves?

A
  • amount of photosynthesis that can take place decreases as day length decreases + temp decreases so amount of glucose produced decreases
  • amount of glucose needed for respiration to maintain leaves through the winter + produce chemicals of prevent freezing damage increases
  • becomes more efficient to lose their leaves + become dormant until temp + day length increases
29
Q

Abscission?

A
  • falling light levels
  • decreases conc of auxin
  • leaves produce ethene
  • ethene initiates gene switching in abscission zone at base of leaf stalk
  • causes production of new enzymes
  • digest + weaken cell walls in outer layer
  • vascular bundles sealed off
  • fatty material deposited in cells
  • this layer form protective scar when leaf falls preventing pathogen entry
  • cells in separation zone respond to hormonal cues by retaining water + swell
  • more strain on outer layer
  • further abiotic processes finish
  • strain too much + leaf separates leaving meat waterproof scar

Biology (26 decks)

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