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Biology GCSE > plant structures and their functions > Flashcards

plant structures and their functions Flashcards

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1
Q

why do plants photosynthesise

A

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

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2
Q

where does photosynthesis occur

A

the chloroplasts

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3
Q

word reaction photosynthesis

A

carbon dioxide + water -> glucose + oxygen

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4
Q

symbol reaction photosynthesis

A

6CO2 + 6H2O -> C6H12O6 + 6O2

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5
Q

what kind of reaction is photosynthesis

A

endothermic reaction (takes in energy)

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6
Q

what are the three 3 limiting factors of PHOTOSYNTHESIS

A

temperature
light intensity
carbon dioxide concentration

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7
Q

how does temperature affect photosynthesis

A

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

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8
Q

how does light intensity affect photosynthesis

A

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

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9
Q

what is the inverse square law

A

light intensity ∝ 1/ distance ^2

light intensity and distance from light source are inversely proportional

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10
Q

how does CO2 concentration affect photosynthesis

A

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

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11
Q

describe the pondweed experiment to measure the rate of photosynthesis

A

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

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12
Q

rate of oxygen production formula

A

rate of oxygen production = volume produced/time taken

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13
Q

adaptations of root hair cells

A

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

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14
Q

role of phloem cells

A

where translocation occurs

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

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15
Q

translocation

A

the movement of sucrose and other substances

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16
Q

structure of phloem cells

A

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

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17
Q

role of xylem cells

A

part of the transpiration stream

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

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18
Q

structure of xylem cells

A

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

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19
Q

transpiration

A

the loss of water from a plant

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20
Q

descirbe the transpiration stream

A

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

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21
Q

stomata

A

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

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22
Q

how does water vapour escape through the stomata

A

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

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23
Q

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

A

flaccid - stomata close

turgid - stomata open

24
Q

what 3 environmental factors affect transpiration rate

A

light intensity
temperature
air flow

25
Q

how does light intensity affect transpiration rate

A

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

26
Q

how does temperature affect transpiration rate

A

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

27
Q

how does air flow affect transpiration rate

A

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

28
Q

potometer

A

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

29
Q

how to set up a potometer to measure transpiration wate

A

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

30
Q

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

A 
waxy cuticle
upper epidermis
palisade mesophyll tissue
spongy mesophyll tissue
lower epidermis
31
Q

give 6 adaptations of the leaf

A

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

32
Q

adaptations

A

features that help an organism to survive in its environment

33
Q

give 3 adaptations that help to reduce water loss by evaporation

A

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

34
Q

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

A

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
35
Q

give an adaptation of plants to store water

A

having a thick, fleshy stem

36
Q

auxins

A

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

37
Q

what do auxins in the roots do

A

inhibit growth

38
Q

what do auxins in the shoots do

A

promote growth

39
Q

where are auxins produced

A

in the tips and they diffuse backwards to stimulate cell elongation

40
Q

phototropism

A

growth responses of plants to light

41
Q

gravitropism

A

growth responses of plants to gravity

42
Q

describe the tropisms of shoots

A

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

43
Q

describe the tropisms of roots

A

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

44
Q

to investigate tropisms

A

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

45
Q

what are two commercial uses of auxins

A

selective weedkillers

rooting powder

46
Q

selective weedkillers

A

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

47
Q

rooting powder

A

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

48
Q

what are three commercial uses of gibberellins

A

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

49
Q

gibberellins

A

plant hormones that stimulate seed germination, stem growth and flowing

50
Q

germination ( at unusual time of year )

A

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

51
Q

seedless fruit

A

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

52
Q

fruit and flower formation

A

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

53
Q

one commercial use of ethene

A

ethene is a ripening hormone

fruits that have been picked whilst unripe can be ripened to perfection as it arrives in the supermarkets

54
Q

how do stomata open

A

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

55
Q

how do stomata close

A

guard cells lose water via osmosis
they become flaccid
stomata close

Biology GCSE (8 decks)

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