plant structures and their functions

Question 1

why do plants photosynthesise

Answer 1

they use energy from the Sun to make glucose which allows the plant to make more complex molecules needed for it to grow so is responsible for its increase in biomass

Question 2

where does photosynthesis occur

Answer 2

the chloroplasts

Question 3

word reaction photosynthesis

Answer 3

carbon dioxide + water -> glucose + oxygen

Question 4

symbol reaction photosynthesis

Answer 4

6CO2 + 6H2O -> C6H12O6 + 6O2

Question 5

what kind of reaction is photosynthesis

Answer 5

endothermic reaction (takes in energy)

Question 6

what are the three 3 limiting factors of PHOTOSYNTHESIS

Answer 6

temperature
light intensity
carbon dioxide concentration

Question 7

how does temperature affect photosynthesis

Answer 7

if a plant gets too hot, the enzymes needed for photosynthesis will be denatured
this occurs at about 45°C

Question 8

how does light intensity affect photosynthesis

Answer 8

at first as light level is raised, the rate of photosynthesis increases up to a point (directly proportional)

Question 9

what is the inverse square law

Answer 9

light intensity ∝ 1/ distance ^2

light intensity and distance from light source are inversely proportional

Question 10

how does CO2 concentration affect photosynthesis

Answer 10

increasing CO2 concentration increases rate of photosynthesis up to a point
after which light intensity or temperature need to be increased

Question 11

describe the pondweed experiment to measure the rate of photosynthesis

Answer 11

1) set up an LED lamp at different distances from the plant in a beaker of water with SODIUM HYDROGEN CARBONATE added to it (to provide the CO2 reactant)
2) pondweed is left to photosynthesise for set period of time
3) oxygen released is collected in the gas syringe so volume can be accurately measured OR oxygen bubbles could be counted but its less accurate
4) repeat experiment at different distances

Question 12

rate of oxygen production formula

Answer 12

rate of oxygen production = volume produced/time taken

Question 13

adaptations of root hair cells

Answer 13

hairs stick out into the soil

they have a large surface are which increases absorption of water via osmosis and mineral ions via active transport

Question 14

role of phloem cells

Answer 14

where translocation occurs

transports food substances, mainly sucrose, made in the leaves to immediate use or storage

Question 15

translocation

Answer 15

the movement of sucrose and other substances

Question 16

structure of phloem cells

Answer 16

LIVING cells (elongated) with small pores in the end walls which allow substances to flow through

Question 17

role of xylem cells

Answer 17

part of the transpiration stream

take water up from the roots , transporting water and minerals (dissolved in it)

Question 18

structure of xylem cells

Answer 18

dead cells joined end to end with no end walls and a hole down the middle
strengthened with lignin

Question 19

transpiration

Answer 19

the loss of water from a plant

Question 20

descirbe the transpiration stream

Answer 20

water evaporates at the leaves leaving a slight shortage of water in the leaf
more water is therefore drawn up from the xylem to replace it
in turn, more water is drawn up from the roots so there is a constant transpiration stream
the transpiration stream carries water and the mineral ions dissolved in it

Question 21

stomata

Answer 21

tiny pored on the underside of a leaf that allow gas exchange and water vapour to escape

Question 22

how does water vapour escape through the stomata

Answer 22

water escapes via diffusion because there is more inside the plant than outside

Question 23

if the guard cells are flaccid/turgid, what state are the stomata in

Answer 23

flaccid - stomata close

turgid - stomata open

Question 24

what 3 environmental factors affect transpiration rate

Answer 24

light intensity
temperature
air flow

Question 25

how does light intensity affect transpiration rate

Answer 25

the brighter the light, the greater the transpiration rate - stomata start to close as it gets darker as photosynthesis can't happen so CO2 doesn't need to be released and very little water can therefore escape

Question 26

how does temperature affect transpiration rate

Answer 26

the warmer it is, the greater the transpiration rate | when its warm , water particles have more energy to evaporate and diffuse out of the stomata

Question 27

how does air flow affect transpiration rate

Answer 27

the better the air flow, the greater the transpiration rate with poor air flow, the water vapour doesn't move away from the leaf - there is a high concentration of water outside so diffusion is slower

Question 28

potometer

Answer 28

measures water uptake by a plant which is assumed to be directly related to the water being lost by transpiration

Question 29

how to set up a potometer to measure transpiration wate

Answer 29

beak of water connected to a capillary tube with a scale which flows into a tube containing a plant record the bubble in the capillary tube's starting position start a stopwatch and record the distance moved per unit of time by the bubble

Question 30

what are the 5 layers of the leaf (from top to bottom)

Answer 30

``` waxy cuticle upper epidermis palisade mesophyll tissue spongy mesophyll tissue lower epidermis ```

Question 31

give 6 adaptations of the leaf

Answer 31

broad leaves - large surface area for absorbing light for photosynthesis palisade layer - lots of chloroplasts near the top of the leaf to absorb lots of light transparent upper epidermis - lets light pass through to the palisade layer xylem and phloem form supportive structure to provide water and remove glucose waxy cuticle reduces loss of water by evaporation lower epidermis has lots of stomata and spongy mesophyll has lots of air space which makes gas exchange more efficiently

Question 32

adaptations

Answer 32

features that help an organism to survive in its environment

Question 33

give 3 adaptations that help to reduce water loss by evaporation

Answer 33

small leaves or spines ( reduces surface area for water loss and spines deter animals from eating it and consuming water) thick, waxy cuticle fewer stomata/stomata only open at night

Question 34

give two adaptations that help to reduce air flow near the leaf

Answer 34

stomata sunken in pits curled leaves or leaves with hairs on the surface - both of these adaptations trap water vapour and reduce diffusion from leaf to air

Question 35

give an adaptation of plants to store water

Answer 35

having a thick, fleshy stem

Question 36

auxins

Answer 36

plant hormones controlling growth of roots and shoots ; move through solution

Question 37

what do auxins in the roots do

Answer 37

inhibit growth

Question 38

what do auxins in the shoots do

Answer 38

promote growth

Question 39

where are auxins produced

Answer 39

in the tips and they diffuse backwards to stimulate cell elongation

Question 40

phototropism

Answer 40

growth responses of plants to light

Question 41

gravitropism

Answer 41

growth responses of plants to gravity

Question 42

describe the tropisms of shoots

Answer 42

positively phototropic - accumulates auxins on the SHADED side so cells elongate on the shaded size, forcing it to bend towards the light negative gravitropic - when a shoot is growing sideways, the auxin is unevenly distributed along the lower side so the lower side grows faster, forcing the shoot to bend up

Question 43

describe the tropisms of roots

Answer 43

negatively phototropic - auxins accumulate on the shaded side where they inhibit cell elongation so the root bends away from the light positively gravitropic - when growing sideways, they gather on the lower side, inhibiting growth so cells on the top elongate faster causing the root to grow downwards

Question 44

to investigate tropisms

Answer 44

1) place cress seeds in a petri dish with moist filter paper 2) surround with black card 3) cut a hole in one side of the card and shine a light through it 4) leave the cress for a week and observe the plant's response

Question 45

what are two commercial uses of auxins

Answer 45

selective weedkillers | rooting powder

Question 46

selective weedkillers

Answer 46

commercial use of auxins only affect broad leaved plants , often weeds they disrupt regular growing patterns, soon killing them but leaving everything else untouched

Question 47

rooting powder

Answer 47

commercial use of auxins allows a cutting to rapidly produce roots and start growing as a new plant growers can produce lots of clones quickly

Question 48

what are three commercial uses of gibberellins

Answer 48

germination (at unusual times of year) seedless fruit fruit and flower formation

Question 49

gibberellins

Answer 49

plant hormones that stimulate seed germination, stem growth and flowing

Question 50

germination ( at unusual time of year )

Answer 50

commercial use of gibberellins many seeds won't germinate if they have endured a period of cold and dark using gibberellins can cause them to germinate at unusual times of year, enabling crop production year round

Question 51

seedless fruit

Answer 51

commercial use of gibberellins if a flower isn't pollinated, the fruit and seeds won't grow using gibberellins, the fruit is produced without the seeds

Question 52

fruit and flower formation

Answer 52

commercial use of gibberellins gibberellins can be used to stimulate germination in a plant flower when it wouldn't normally they can reduce flower formation by causing few plants to flower so higher quality fruit is produced

Question 53

one commercial use of ethene

Answer 53

ethene is a ripening hormone | fruits that have been picked whilst unripe can be ripened to perfection as it arrives in the supermarkets

Question 54

how do stomata open

Answer 54

guard cells take in water via osmosis they become turgid stomata open

Question 55

how do stomata close

Answer 55

guard cells lose water via osmosis they become flaccid stomata close