C3.1 Integration of body systems and plants (HL)

Question 1

tropism

Answer 1

growth responses to stimuli

Question 2

positive tropism

Answer 2

growing towards the stimulus

Question 3

negative tropism

Answer 3

growing away from the stimulus

Question 4

positive phototropism

Answer 4

in shoots
caused by hormone called auxin
the side of the plant furthest from the sun grows at a faster rate in order to allow it to bend towards light

Question 5

Phytohormones

Answer 5

plant hormone
growth
- promote/inhibit cell division or elongation
- ex: gibberellin causes stem elongation
development
- promote/inhibit differentiation of plant tissues
- ex: ethylene ripens fruit
response to stimuli
- control tropism
- ex: auxin controls phototropism

Question 6

auxin

Answer 6

a phytohormone that controls tropism; can easily enter the cell through diffusion
produced in shoots and transported to roots

Question 7

auxin efflux carriers

Answer 7

transmembrane proteins that pump auxin out of the cell
can move around within the membrane
cells must coordinate to get high concentrations of auxin in the area where it needs to be

Question 8

plant cell elongation

Answer 8

auxin promotes proton pump synthesis
pumps protons into apoplast
lowers pH (acidification)
weakens cell wall
cell wall can elongate

Question 9

apoplast

Answer 9

outside cell wall

Question 10

cytokinin

Answer 10

another phytohormone; produce in roots and transported to shoots

Question 11

cytokinin and auxin

Answer 11

sometimes work together sometimes work antagonistically (only one benefits)
ensure root and shoot growth are coordinated

Question 12

positive feedback in fruit ripening

Answer 12

fruit ripens to aid in seed dispersal
color change, softening, scent production
ethylene is a phytochrome that works in a positive feedback loop to ripen fruit
it is a gas, so it also affects nearby fruits (synchronisation)