5.1.5 Plant Responses

Question 1

thigmonastic repsonse

Answer 1

touch, non- directional repsonse

Question 2

three structural defences a plant may have to discourage by herbviores

Answer 2

spikes, thorns, barbs - may cause pain or introduce poison/allergen into herbivore
lignin - woody, impermeable molecule that is difficult to eat + digest

Question 3

pheromones

Answer 3

gases that influence the behaviour of members of the same species or herbivores

Question 4

tropism

Answer 4

a directional growth response towards a stimulus

Question 5

positive phototropism

Answer 5

shoots grow towards light
obtain light energy for photosynthesis

Question 6

negative phototropism

Answer 6

roots grow away from light

Question 7

positive phototropsim

Answer 7

roots grow towards gravity
plants can gain water/mineral ions from soil

Question 8

negative geotropsim

Answer 8

shoots grow away from gravity

Question 9

thigmotropism

Answer 9

response to touch
e.g. vine growing around a wooden pole - supportive for plant

Question 10

hydrotropism

Answer 10

growth towards water
water is a reactant for photosynthesis

Question 11

nastic repsonse

Answer 11

non - directional repsonse to a stimulus
may or may not include growth

Question 12

how might thigmonastic repsonses in plants help them to survive

Answer 12

discourage predation by insects
protection against fire - decrease SA exposed

Question 13

auxins (IAA) site of production and effects

Answer 13

shoot tips - promote cell elongation
roots - inhibit cell elongation
shoots- inhibits leaf abscission
apical bud - promotes apical dominance

Question 14

gibberellins site of production and effects

Answer 14

seed - stimulates germination (causing digestive enzymes to be synthesised)

Question 15

why do plants use chemical defences against herbivores

Answer 15

provides a bitter taste to the herbivore to deter it
poisionous - disrupts metabolism, acts as non-competitive enzyme inhibitors