Plant response to the environment

Question 1

Define plant hormones?

Answer 1

chemicals that regulate the growth and differentiation of plant cells and tissues

Question 2

how do plants respond?

Answer 2

have hormones which respond to stimuli in environment such as light, co2. o2, gravity and chemicals

Question 3

Explain the 3 functions of auxins?

Answer 3

promote growth through cell division and elongation

promote apical dominance, ie auxins produced at apical bud, inhibits growth of lateral branches on top, lower stem has less auxins which allow more growth of lateral branches. therefore tapered growth and no competition for light

promotes tropic movements

Question 4

Where is auxin hormone produced?

Answer 4

apical bud, meristem and root tip

Question 5

What happens if apical bud is removed?

Answer 5

lateral branches will grow on top as there are no auxins produced to inhibit it. therefore more fruits for crops

Question 6

Define tropisms?

Answer 6

growth of parts of plants in response to external stimuli

Question 7

What is phototropism and explain the process? (4)

Answer 7

growth movement of plant toward light stimulus

• when unilateral light is shone on a plant from a direction
• the auxins will move toward the shaded region (higher concentration)
• promotes cell elongation on shaded region, therefore more growth
• plant bends toward light (positively phototropic)
  roots are negatively phototropic

Question 8

How do phototropic movements benefit the plant?

Answer 8

seed dispersal
photosynthesis
flower pollination

Question 9

explain geotropic movements

Answer 9

growth movements of plants in response to gravity

Question 10

Functions of gibberllins?

Answer 10

plant hormones that promotes seed Germination
allows for upward growth of stem
and promote developments of flowers

Question 10

Geotropism Upright VS horizontal(root/stem)

Answer 10

upright- auxins move evenly downward and promote growth across an even distribution, allowing root to grow down and stem to grow up

horizontal, auxins are pulled to lower side of plant. in stems it promotes growth on the lower side allowing stem to bend upward (negative geotropism)
in roots, auxins inhibit growth on lower side and therefore upperside root elongates and root moves downward.
positively geotropic

Question 11

What is abscisic acid and functions?

Answer 11

hormone that inhibits growth in adverse conditions
- allows apical bud to be dormant and seed dormant until correct conditions- hence prevent damage to apical bud

Question 12

How are hormones used to control weeds?

Answer 12

weeds take up nutirents and damage soil for crops
herbicides can be toxic to other plants or humans
so auxins are selectively used
the have no affect on narrrow leaved plants
but kill broad leaved plants by making them grow at an unsustainable rate
hence weeds can die out for crops to grow

Question 13

why are plant defence mechanisms needed?

Answer 13

protect to survive from pathogens and herbivores

Question 14

Plant chemical defence?

Answer 14

chemicals produced to deter pathogens and herbivores, poison and toxic that stop feeding and survival of herbivores

Question 15

Plant physical defence?

Answer 15

physical structures to protect from being eaten
thorns that hurt mouths
prickles- extensions of epidermis to hurt
spines in leaves to protect