3.6.1.1 Plant responses Flashcards

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1
Q

Phototropism

A
  • shoots are positively phototrophic & grow toward sunlight

- roots are negatively phototrophic & grow away from light

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2
Q

Geotropism

A
  • shoots are negatively geotropic & grow upwards

- roots are positively geotropic & grown downwards

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3
Q

How do auxins stimulate growth of shoots?

A
  • by cell elongation
  • auxins stimulate proton pumps in the cell membrane
  • protons are pumped into the cell wall from the cytoplasm
  • the protons activate expansins (proteins / enzymes)
  • expansins break some of the hydrogen bonds between chains of cellulose
  • cell walls become ‘ loose and stretchy’ so the cells become longer
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4
Q

How do auxins affect root growth?

A

inhibit root growth

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5
Q

How do plants detect the direction of gravity?

A
  • cells near root tips contain amyloplasts (dense organelles / starch grains)
  • amyloplasts sink to the bottom of the cell they are in
  • this enables the creels to detect the direction of gravity
  • IAA is actively transported to the location of the amyloplasts
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