Mr Dewhurst- plant responses

Question 1

what is abiotic stress

Answer 1

non-living factors: drought, too much water, high/low temp, light intensity

Question 2

how does leaf loss in deciduous benefit the tree ( 4 reasons)

Answer 2

low temp-low enzyme activity- less photosynthesis- no need for leaves
keep water from freezing at roots so cells don’t burst
glucose needed to prevent freezing is more than produced during photosynthesis so loosing leaves reduces stress for glucose
leaves drop- leaves die-nutrients go into roots

Question 3

what are pheromones and an example of maple tree

Answer 3

chemicals which when released affect the behaviour of others of the same species.
maple trees- release a pheromone which is absorbed by other nearby leaves to make callose which will protect themselves if attacked.

Question 4

what is trophism

Answer 4

growth towards an external stimulus

Question 5

what is a nastic response

Answer 5

non-directional growth

Question 6

what is positive phototropism

Answer 6

shoots grow towards light

Question 7

what is negative geotropism

Answer 7

shoots grow up

Question 8

what is positive geotropism

Answer 8

roots grow down (gravity)

Question 9

how are plant responses controlled

Answer 9

hormones are not produced by glands, instead variety of tissue when reach target cell they bind to receptors that can influence cell division, elongation and differentiation

Question 10

what signalling molecule allows plants to respond to environmental changes

Answer 10

plant hormones

Question 11

what is the name for a plant that looses its leaves seasonally

Answer 11

deciduous

Question 12

what is ethene responsible for

Answer 12

stimulates leaf loss
causes abscission layer causing cells to expand and break cell walls by stimulating enzyme cellulase which breaks cellulose

Question 13

what is auxin

Answer 13

plant hormone made in the tip of the roots and shoots, unequally distributes in response to light/ gravity, elongates cells
prevents production of ethene

Question 14

if the plant grows straight what is the distribution of auxin

Answer 14

even on both sides of the shoot

Question 15

when the shoot bends to light which side is auxin produced

Answer 15

the shaded side, causing the cells to elongate and bend.

Question 16

what is the difference between auxin distribution in the roots vs shoots

Answer 16

opposite- roots the auxin is on the bottom (gravity) and they prevent growth making the roots bend down as opposite side to auxin elongates

Question 17

what is the apical bud and where is it in the plant

Answer 17

located at the apex (top)
apical bud produces auxin- stops lateral buds from growing so the plant grows taller to access sunlight

Question 18

what are the lateral buds and how do they grow

Answer 18

grow the plant outwards- grows when apical bud is cut

Question 19

what did Darwin conclude about his observation phototropism

Answer 19

the tip is what detects the light to bed the plant

Question 20

what did Boysen-Jenesen conclude about his observations

Answer 20

chemical in the tip causing it to bend is down the shaded side as the sheet of mica stops chemicals passing so the shoot didn’t bend but when the sheet was on the other side it did bend towards the light

Question 21

what did Went conclude about his observations

Answer 21

agar has absorbed chemical that makes it bend from tip.

Question 22

what is abscisic acid

Answer 22

abscisic acid prevent buds from growing as high auxin means high abscisic acid
when auxin is removed, abscisic acid levels drop causing buds to grow

Question 23

what do cytokinin’s do

Answer 23

cause buds to grow, so high levels of auxin means cytokinin’s move to shoot apex, but when removed it spreads out evenly

Question 24

what do gibberellins do

Answer 24

initiates seed germination- seed absorbs water which causes embryo to release gibberellins which produce amylase to break down starch into glucose for respiration (growth)

Question 25

what is meant by synergistic hormones

Answer 25

work together to make plant tall

Question 26

what are antagonistic hormones and example

Answer 26

work against each other
e.g. gibberellin- promotes side shoots
auxin- inhibits side shoots

Question 27

What is the commercial use of ethene specifically in supermarkets

Answer 27

Ripening of climacteric fruits which continue to ripen even after cut, the peak triggers a series of chemical reactions increasing respiration rate.
Supermarkets- cut fruits well before they are ripe so can be transported easily without being damaged as it is hard. When ready to sell they are sprayed with ethane gas to ensure all fruit ripens at same rate.

Question 28

What is the commercial use of ethene specifically in supermarkets

Answer 28

Ripening of climacteric fruits which continue to ripen even after cut, the peak triggers a series of chemical reactions increasing respiration rate.
Supermarkets- cut fruits well before they are ripe so can be transported easily without being damaged as it is hard. When ready to sell they are sprayed with ethane gas to ensure all fruit ripens at same rate.

Question 29

What are climacteric fruits and non-climacteric fruits

Answer 29

Climateric- high amounts of ethene so continue to ripen after being cut
Non-climacteric- fruit that doesn’t produce much ethene so doesn’t continue to ripen

Question 30

What hormone is used for rooting powder and how does it work

Answer 30

Auxin, stimulates production of roots so when applied to cutting it increases chance of roots growing, this is helpful for the horticulture community so thousands of new plants can be grown from one original plant,

Question 31

how do hormonal weed killers work

Answer 31

synthetic auxins are applied to broad-leaved plants and affect metabolism as growth rate increases, they become unsustainable so die but doesn’t effect narrow-leaved crops like rice so continue to grow free from competition, farmers use them as they are cheap, not damaging to mammals.

Question 32

why are wed threats to other plants

Answer 32

they are in competition for food, light, spaced and water

Question 33

what other uses are there of plant hormones

Answer 33

auxin- produces seedless fruits
ethene- promote fruit dropping
cytokinin’s- prevent ageing of ripened fruit
gibberellins- delay ripening and ageing in fruit, improves size and shape and speeds up malting in beer brewing process.