Plant Hormones (paper 2)

Question 1

2 factors

plants produce hormones to coordinate and control:

Answer 1

• groth and response to light - phototropism
• growth responses to gravity - gravitropism / geotropism

Question 2

what causes unequal growth rates in plant roots and shoots

Answer 2

unequal distribution of auxin

Question 3

what is the effect of auxin on shoots

Answer 3

to grow / elongate more quickly

Question 4

what is the effect of auxin on roots

Answer 4

causes cells in roots to grow more slowly

Question 5

name 3 plant hormones:

Answer 5

• auxin
• gibberellins
• ethene

Question 6

what ae gibberellins used for

Answer 6

important in initiating seed germination

Question 7

what is ethene used for

Answer 7

controls cell division and ripening of fruits

Question 8

what is positive tropism

Answer 8

growth towards a stimulus

Question 9

what is negative tropism

Answer 9

growth away from a stimulus

Question 10

plant shoots and roots respond to which 3 stimuli

Answer 10

• light
• gravity
• water

Question 11

phototropism =

Answer 11

plant shoots bend / grow in response to light

Question 12

describe the stages of phototropism

Answer 12

• when light falls evenly on the shoot –> auxin is spread evenly through the tissues
• when light falls on shoots from one direction –> auxin moves away from light - accumulates on the shaded side of the shoot = now an uneven distribution of auxin
• auxin causes cells on shaded side to grow faster than cells on the side in the light –> causes shoot to bend towards the light
• when ** light falls evenly** on shoots again, –> auxin becomes evenly distributed = growth on all side of the root and shoot will be equal

Question 13

gravitropism =

Answer 13

the response of a plant to gravity

Question 14

describe the process of gravitropism when a young plant is laid on its side.

Answer 14

1. auxin accumulates on the lower side of both the root + shoot = uneven distribution of auxin
2. Roots: cells elongate faster on the side will less auxin - causes the roots to bend downwards - direction of the force of gravity
3. Shoots: cells elongate faster on the side with more auxin - shoots bend upwards - away from gravity
4. once roots is growing towards gravity + shoots is growing away from gravity - auxin becomes evenly distributed = growth on all side of the root + shoot will be equal

Question 15

RPA 8 investigate the efffect of light / gravity on the growth of newly

describe the stages of phototropism

Answer 15

• auxin is produced in the shoot tips
• ausin diffuses to the shaded dise
• the concentration of auxin on the shaded side increases - unequal aucin distribution
• the higher concentration of auxn causes the cell on the shaded side to increas their length
• causes shoot tipe to bend towards light - shoot tips shows positive phototropism

Question 16

RPA 8

there are 3 groups of seeds in a cardbaord box, with a hole that allows light into the box from one side onlyL=:
- Group A has had shoot tips removed
- Group B has had shoot tips covered
- Group c is left untouched
What will be the growth results of each seed group?

Answer 16

A = no auxin is made so stems do not grow
B - auxin moves to all part of the stem causing all parts to grow equally - grows straight up
C - auxin acculumates on the shaded side causing it to grow more than the illuminated side - grows towards light

Question 17

where are plant growth hormones used

Answer 17

in agriculture and horticulture

Question 18

3 ways in which auxin is used and how:

Answer 18

• weed killers
  
  • very high doses causes plants to grow too quickly + die
• rooting powder
  
  • encourage meristem in cuttings to grow into new roots
• promoting growth in tissue culture
  
  • encourage formation of rootlets + shootlets

Question 19

what is ethene used for

Answer 19

• in the food industry to control ripening of fruit during storage + transport

Question 20

what effect does ethene have on agriculture, transportation, sale

Answer 20

• unripe fruit can be picked + transported –> damages less easily + lasts longer
• fruit can be ripened with ethene at its destination so that it is ready to eat + look appealing for sale

Question 21

what are gibberellins used for

Answer 21

• end seed dormancy
• promote flowering
• increase fruit size

Question 22

how does the use hormones as weed killers has an effect on biodiversity.

Answer 22

selective weedkillers kill specific plants that some species of animals rely on as a food source –> reduction of biodiversity