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BIOLOGY > Plant Structures and Their Functions - TOPIC 6 > Flashcards

Plant Structures and Their Functions - TOPIC 6 Flashcards

1
Q

what is photosynthesis

A

an endothermic reaction that uses light energy to react carbon dioxide and water to produce glucose and oxygen

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2
Q

what are photosynthetic organisms

A

the main producers of food and therefore biomass

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3
Q

what is biomass

A

the mass of living material in the organisms

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4
Q

where does photosynthesis occur

A

in chloroplasts

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5
Q

what is the word equation for photosynthesis

A

carbon dioxide + water —–> glucose + oxygen

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6
Q

what is the symbol equation for photosynthesis

A

6CO2 + 6H20 ——> C6H1206 + 602

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7
Q

what are the limiting factors on the rate of photosynthesis

A

effect of light intensity
carbon dioxide concentration
temperature

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8
Q

how does light intensity affect rate of photosynthesis

A

as light intensity increases, rate of photosynthesis increases

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9
Q

why does increasing light intensity after a certain point make no difference to the rate of photosynthesis

A

either the temp or carbon dioxide level will become the limiting factor

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10
Q

how does carbon dioxide concentration affect the rate of photosynthesis

A

as carbon dioxide concentration increases, the rate of photosynthesis increases

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11
Q

why does the amount of carbon dioxide only increase the rate of photosynthesis up until a point

A

temperature or light intensity will now be the limiting factor

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12
Q

how does temperature affect the rate of photosynthesis

A

as temp increases, the rate of photosynthesis increases but if it gets too hot the reaction slows down or stops

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13
Q

how do you investigate the effect of light intensity on the rate of photosynthesis

A
  1. A source of white light is placed a specific distance away from a conical flask with pondweed
  2. Leave the pondweed for a few minutes
  3. Connect a gas syringe to the conical flask
  4. Oxygen released will collect in the syringe
  5. Repeat a few times with light source at same distance and calculate mean volume of oxygen produced

6, repeat experiment with light source at different distances

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14
Q

what is the independent variable in the investigation

A

light intensity

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15
Q

what is the dependant variable in the investigation

A

amount of oxygen produced

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16
Q

what is a dependant variable

A

the variable you are measuring

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17
Q

how do you calculate the rate of photosynthesis

A

total volume of gas produce / time taken

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18
Q

what is the inverse square law

A

light intensity is proportional to 1/distance^2

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19
Q

the rate of photosynthesis is directly proportional to ……..

A

light intensity

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20
Q

what is the function of the phloem

A

phloem tubes transport food substances made in the leaves to the rest of the plant for immediate use OR for storage

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21
Q

how is the phloem adapted to its function

A

it is made of living cells that are supported by companion cells AND have holes in the end cell walls which allow sugars and amino acids to flow easily through

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22
Q

what is the function of the xylem

A

xylem tubes carry water and mineral ions up the plant from the roots to the stems and leaves

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23
Q

how is the xylem adapted to its function

A

xylem tubes are made of dead cells joined end to end with no end walls between them and strengthened with lignin

24
Q

how are water and mineral ions transported through the plant by transpiration

A
  1. water inside a leaf evaporates and diffuses out of the leaf, mainly through the stomata
  2. This creates a slight shortage of water in the leaf, so more water is drawn up from rest of plant through xylem vessels
  3. This means more water is drawn up from the roots, so there is constant transpiration stream of water through the plant
  4. transpiration stream carries mineral ions dissolved in water
25
Q

how is the structure of root cells adapted to absorb water and mineral ions

A

the hairs give the plant a large SA to absorb water and mineral ions

conc of mineral ions is higher in root hair cells than in soil, so mineral ions are absorbed by active transport

there is more water in soil than in roots, so water is absorbed by osmosis

26
Q

what environmental factors affect transpiration rate

A

light intensity
temperature
air flow

27
Q

how does light intensity affect transpiration rate

A

the brighter the light, the greater the transpiration rate

28
Q

why is transpiration rate lower in the dark

A

in the dark, stomata begin to close and so very little water can escape

29
Q

how does temperature affect transpiration rate

A

the warmer it is, the faster transpiration happens

30
Q

why is transpiration rate faster when it’s warmer

A

when it is warm, the water particles have more energy to evaporate and diffuse out of the stomata

31
Q

how does air flow affect transpiration rate

A

the better the air flow around a leaf, the greater the transpiration rate

32
Q

why is transpiration rate faster with better air flow

A

water vapour gets swept away, maintaining a low concentration of water in the air outside of the leaf and then diffusion happens quickly

33
Q

what is the function of the stomata

A

they allow carbon dioxide and oxygen to diffuse directly in and out of a leaf/gas exchange and allow water vapour to escape during transpiration

34
Q

where are stomata found

A

on the lower surface of leaves

35
Q

what is the structure of guard cells

A

they have a kidney shape which helps to open and close the stomata

36
Q

how do guard cells open the stomata

A

when the plant has lots of water, guard cells fill with water and go turgid. This opens the stomata.

37
Q

how do guard cells close the stomata

A

when the plant is short of water, guard cells lose water and become flaccid, closing the stomata

38
Q

why are stomata found more commonly on the underside of leaves

A

the lower side is shaded and cooler, so less water is lost through the stomata than if they were on the top

39
Q

what are the adaptations of guard cells

A

thin outer walls and thickened inner walls
they are sensitive to light

40
Q

how is the leaf adapted to make photosynthesis efficient

A

epidermal tissues have a thick waxy cuticle
upper epidermis is transparent
leaves are broad
xylem and phloem

41
Q

how does the waxy cuticle make photosynthesis efficient

A

it reduces water loss from the leaf by evaporation

42
Q

how does the transparent upper epidermis make photosynthesis efficient

A

light can pass through it to the palisade layer

43
Q

how do broad leaves make photosynthesis more efficient

A

large SA exposed to light

44
Q

how is the leaf adapted for efficient gas exchange

A

lower epidermis is full of stomata

air spaces in spongy mesophyll increase rate of diffusion of gases

45
Q

what are the plant adaptations for extreme adaptations

A

small leaves or spines
curled leaves
thick waxy cuticle
thick and fleshy stems
only a few stomata
stomata sunken in pits

46
Q

what are auxins

A

plant hormones which control growth near tips of shoots and roots

47
Q

what do auxins control

A

phototropism
gravitropism

48
Q

what is phototropism

A

plant growth in response to light

49
Q

what is gravitropism

A

plant growth in response to gravity

50
Q

how do shoots grow towards light

A

when a shoot tip is exposed to light, auxins accumulate on the side in the shade so the cells grow faster on the shaded side, so the shoot bends towards the light

51
Q

how do shoots grow away from gravity

A

when a shoot is growing sideways, gravity produces an unequal distribution of auxin in the tip, with more auxins on the lower side so lower side grows faster, bending the shoot up

52
Q

how do roots grow towards gravity

A

when a root is growing sideways, more auxins accumulate on lower side and the extra auxin inhibits growth so the cells on the top elongate faster and root bends down

53
Q

what are the commercial uses of auxins

A

selective weedkillers
growing from cuttings with rooting powder

54
Q

what are the commercial uses of gibberellins

A

controlling flower and fruit formation
controlling seed germination
producing seedless fruit

55
Q

what is the commercial use of ethene

A

it is used in fruit ripening

BIOLOGY (9 decks)

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