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edexcel igcse biology > section c: plant physiology > Flashcards

section c: plant physiology Flashcards

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1
Q

what is photosynthesis

A

the process where carbon dioxide and water are combined to make carbohydrates (glucose) using light energy. oxygen is formed as a waste product.

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2
Q

what is chlorophyll

A

the green molecule contained inside chloroplasts that absorbs sunlight energy in order for photosynthesis to take place.

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3
Q

what is a chloroplast

A

the organelle that contains chlorophyll

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4
Q

cuticle

A

waxy surface of the leaf

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5
Q

what is underneath the cuticle

A

the upper epidermis

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6
Q

what is underneath the upper epidermis

A

palisade cells

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7
Q

what is underneath the palisade cells

A

spongy cells

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8
Q

what is the mesophyll layer

A

the palisade cells and the spongy cells of a leaf

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9
Q

what are guard cells

A

cells surrounding the stoma (a hole within the lower epidermis which allows carbon dioxide in) that can close it when needed.

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10
Q

what is the bottom layer of a leaf

A

the lower epidermis

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11
Q

xylem

A

where water and ions go up to the leaf

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12
Q

phloem

A

supplies the other parts of the plant (roots) with the products of photosynthesis (food)

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13
Q

rate of photosynthesis during the day

A

plants will absorb more carbon dioxide as they have access to more sunlight during the day enabling a higher rate of photosynthesis

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14
Q

what is starch

A

a polysaccharide (a chain of glucose molecules put together)

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15
Q

how do you test a leaf for starch

A
  1. dewax in boiling water
  2. remove colour in boiling ethanol
  3. wash the ethanol off in cold water
  4. put the iodine solution on the leaf.
  5. if it goes blue/black then it contains starch.
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16
Q

sucrose

A

a disaccharide (two glucose molecules put together) that is the main sugar in the phloem.

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17
Q

cellulose

A

a polysaccharide (glucose molecules put together) that forms cell walls

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18
Q

what anions do plants get out of the soil

A

nitrates (NO3 -)
sulfates (SO4 2-)
phosphates (PO4 3-)

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19
Q

what cations do plants get out of the soil

A

calcium (Ca 2+)
magnesium (Mg 2+)
potassium (K +)
iron (Fe 3+)

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20
Q

uses of nitrates in bean plants

A

enzymes
DNA
proteins

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21
Q

nitrate deficiency effects

A

slow growth

older leaves turn yellow

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22
Q

uses of magnesium in bean plants

A

chlorophyll

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23
Q

magnesium deficiency in bean plants

A

leaves turn yellow

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24
Q

hydroponics definition

A

the growing of a plant’s roots in a plastic tube that has a mineral solution in it e.g lettuce or cannabis

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25
Q

what are xylem vessels

A

long hollow tubes made of dead cells arranged end to end forming a continuous channel

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26
Q

what are the holes in the walls of the xylem vessel called

A

pits

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27
Q

what does the xylem vessel contain in its cell wall that adapts it for its function

A

lignin

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28
Q

what does lignin do within a xylem vessel

A

it makes it structurally strong and imperable to water (waterproof)

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29
Q

is the xylem vessel wide or narrow

A

narrow

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30
Q

why is the xylem vessel narrow

A

so that water can be easily transported upwards by capillary action

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31
Q

what are phloem vessels

A

vessels that run alongside the xylem tissue

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32
Q

what are phloem vessels made of

A

specialized and nucleate parenchyma cells
sieve tube cells
companion cells

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33
Q

what is the function of phloem vessels

A

transport nutrients such as glucose and amino acids.

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34
Q

what direction does phloem carry nutrients

A

upwards and downwards. the materials are synthesized in the leaves by photosynthesis and moved to other cells of the plant

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35
Q

where is the nucleus in the phloem

A

in the companion cell

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36
Q

what are the phloems activities controlled by

A

companion cells

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37
Q

do companion cells have a nucleus

A

yes

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38
Q

what do roots absorb

A

water and minerals

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39
Q

water absorption is mainly carried out by

A

root hairs

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40
Q

what do root hairs increase

A

the surface area where water absorption can take place

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41
Q

how does water enter a plant (the two pathways)

A

apoplastic pathway

symplastic pathway

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42
Q

what is the apoplastic pathway

A

when water and minerals move from cell to cell through the spaces between the cell walls

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43
Q

what is the symplastic pathway

A

the water and minerals move across the cytoplasm to reach the xylem

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44
Q

do xylem vessels contain any living material

A

no, only water and soluble mineral salts

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45
Q

how much of the plant’s water is lost through the stomata

A

about 95%

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46
Q

the loss of water from roots to cells then through the stomata is called

A

transpiration

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47
Q

is the number of stomata higher on the top of leaves or the bottom

A

the bottom

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48
Q

what is transpiration caused by

A

the opening of the stomata controlled by guard cells on either side

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49
Q

how do the guard cells control the opoening or closing of the stomata

A

during the day, water and potassium ions go into the guard cells, increasing the turgidity and the stoma changes shape to allow water out. at night the water and potassium ions leave, decreasing turgidity and the stoma closes.

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50
Q

what do plants use the oxygen and carbon dioxide that enters the plant through the stomata for

A

photosyntheisis

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51
Q

osmosis definition

A

the movement of water down a concentration gradient of water through a partially permeable membrane.

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52
Q

what is transpiration

A

the evaporation of water from the surface of a plant.

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53
Q

what is transpiration affected by

A

changes in humidity, wind speed, temperature and light intensity.

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54
Q

what is diffusion

A

the movement of solute molecules down a concentration gradient from a region of higher concentration of solute to a region of lower concentration.

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55
Q

when does osmosis take place

A

when two solutions are separated by a partially permeable membrane.

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56
Q

what is osmolality

A

the number of particles of solute per kg of solvent.

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57
Q

what is osmolarity

A

the number of particles of solute per litre of solution.

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58
Q

water potential definition

A

how free the water molecules are to move

e.g pure water has the highest water potential

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59
Q

if a solution is extremely salty does it have high or low water potential

A

low

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60
Q

what does hypertonic mean

A

the solution is too salty/full of solute

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61
Q

what does isotonic mean

A

when the osmolality of the solution is the same in the cell and the surrounding liquid

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62
Q

what does hypotonic mean

A

the solution is too watery

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63
Q

what happens if you put a plant cell in a hypertonic solution

A

the cell releases water and shrivels up inside

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64
Q

turgor

A

the pressure inside the cell

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65
Q

turgidity definition

A

high pressure and stiff

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66
Q

flaccid definition

A

low pressure and wilting

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67
Q

how does the root absorb mineral ions

A

active transport against the concentration gradient

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68
Q

how does the root absorb water

A

through osmosis (passive)

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69
Q

transpiration process

A

water absorbed by roots
transported by xylem into leaf
in the spongy mesophyll it diffuses into water vapour and is in the air spaces
evaporates out of the leaf due to the concentration gradient

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70
Q

what is the transpiration stream

A

the flow of water from the soil to the root up the xylem to the leaves and out through the stoma

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71
Q

benefits of a transpiration stream to the plant

A

all parts of the plant receive water
all cells remain turgid (which decreases wilting and keeps the stoma open which allows more CO2 in and the plant can make more food)
mineral ions are carried up with the water
evaporation from the leaves keeps them cool

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72
Q

what is the phloem’s structure

A

cells stacked on top of eachother

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73
Q

what are the points of the sieve plates in the phloem’s cell walls

A

it allows for the sucrose/amino acids etc to pass through easier from cell to cell

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74
Q

do phloem cells have a nucleus

A

no

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75
Q

what are phloem cells controlled by

A

the cells next to them (companion cells)

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76
Q

what is the structure of a stem (outside to inside)

A 
epidermis
cortex
a ring of many vascular bundles
(the xylem and phloem are together in a vascular bundle)
Central pith / dead woody lignin
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77
Q

what does vascular mean

A

a vessel

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78
Q

why are more stomata found on the bottom of the leaf and not the top

A

it would lose too much water if they were on the top

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79
Q

why do guard cells close at night

A

they have chloroplasts (which can detect when there isn’t any sun) and close the stoma.

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80
Q

what do the guard cells use the energy captured by the sun by chloroplasts for

A

to actively transport solutes (and therefore water follows) inside and remain turgid and allow the stoma to open

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81
Q

factors that increase rate of transpiration

A

more sunlight
more temperature
higher humidity
higher wind levels

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82
Q

what is a potometer

A

system of measuring rate of transpiration

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83
Q

types of potometer

A

weight

water volume

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84
Q

what is phototropism

A

responses to the stimulus of light

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85
Q

what is geotropism

A

responses to the force of gravity

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86
Q

what is a coleoptile

A

a small cereal shoot

87
Q

how are auxins affected by gravity

A

they drop down the lower side of a plant

88
Q

how do roots and shoots differ in their respone to auxins and geotropism

A

it will inhibit growth in a root causing it to be positively geotropic and cause growth in a plant stem causing it to be negatively geotropic

89
Q

stems have a negative …

A

geotropic response

90
Q

roots have a positive …

A

geotropic response

91
Q

stems have a positive …

A

phototropic response

92
Q

roots have a negative …

A

phototropic response

93
Q

what is the growth response to the stimulus water called

A

hydrotropism

94
Q

what is the stimulus for growth which brings about tropic responses to unidirectional light that is a water - soluble chemical produced in the growing tip

A

auxins

95
Q

what happens to the distribution of auxins when unidirectional light hits a stem

A

auxins build up on the dark side of the shoot

96
Q

how can you show that chlorophyll is needed in photosynthesis

A

use a variegated leaf and draw a pattern of chlorophyll then kill in boiling water, boil in ethanol, rinse in water, and test the leaf for starch using iodine solution. (although products of photosynthesis may have been moved from one part of the leaf to another so this is of limited use.

97
Q

how can you show that carbon dioxide is used in photosynthesis

A

remove carbon dioxide from the air around the plant using soda lime. (although carbon dioxide is made in respiration so this is of limited use.)

98
Q

how is the structure of a leaf adapted for its role as the organ of photosyntheisis

A

thin and flat (for a lot of light absorption and distances for gases to travel are very short)
contain chloroplasts and chlorophyll (especially in the upper palisade cells as more light is received there)
guard cells (more on lower surface to control stomata size)
xylem
spongy mesophyll tissue
large surface area
upper epidermis transparent to let light through

99
Q

why do leaves have a large surface area

A

to absorb as much sunlight as possible

100
Q

why are leaves thin

A

to minimise distance CO2 has to travel

101
Q

why do leaves contain chloroplasts

A

to trap sunlight used in photosynthesis

102
Q

why do leaves contain guard cells

A

to control the opening and closing of the stomata

103
Q

why is spongy mesophyll packed loosely in a leaf

A

for efficent gas exchange. in photosynthesis, CO2 can diffuse in and O2 can diffuse out

104
Q

describe how one named mineral ion helps plants to grow

A

nitrates because they make amino acids which are built up into proteins

105
Q

how does temperature affect the rate of photosynthesis

A

the higher the temperature, the higher the rate of photosynthesis until 37 degrees.

106
Q

how does light intensity affect the rate of photosynthesis

A

drives reactions of photosynthesis so increases it

107
Q

how does carbon dioxide affect the rate of photosynthesis

A

more available, more photosynthesis

108
Q

how would high temperatures reduce growth of plants

A

enzymes denature
more wilting, cells would become less turgid and more flaccid
less CO2 uptake
more transpiration - water deficit and excess water unable to leave plant

109
Q

how does the upper epidermis help the leaf in photosynthesis

A

lets light through

is transparent

110
Q

how do the palisade cells help the leaf in photosynthesis

A

they’re densely packed and contain lots of chloroplasts to trap light

111
Q

how does the spongy mesophyll layer help the leaf in photosynthesis

A

air spaces allow diffusion of gases to leave and enter the cell
it transports water for hydration and removal of water

112
Q

how do guard cells help the plant in photosynthesis

A

they open and close the stomata to let CO2 in and water out

113
Q

why are the stomata found on the bottom of leaves

A

it allows transpiration and evaporation but doesn’t remove too much water.

114
Q

what happens when a cell is placed in a dilute solution

A

it absorbs water by osmosis and becomes turgid

115
Q

what happens when a cell is placed in a concentrated solution

A

it loses water by osmosis and becomes flaccid

116
Q

what does a cell become when it loses excessive water through being placed in a very salty solution

A

plasmolyzed

117
Q

where does osmosis take place

A

across a selectively permeable membrane,

down a water potential gradient

118
Q

why do you use red onion when testing osmosis

A

it doesn’t need to be stained or dyed

119
Q

what could increase rate of water loss

A

temperature
wind speed
low humidity

120
Q

what could decrease rate of water loss

A

humidity
light intensity
spines/hairs

121
Q

washing line experiment

A

to demonstrate tht the majority of water lost from leaves will be through the stomata. the vaseline will block the pores, so the change in mass will show where and how much water is lost

122
Q

for the washing line experiment, why should you calculate the change in mass per cm squared

A

to compare the leaves accurately as they will not all be the same size

123
Q

what indicator do you use to measure the concentration of carbon dioxide

A

hydrogen carbonate indicator

124
Q

what colour will hydrogen carbonate indicator go in a solution with no light and what does this mean

A

it will go yellow as there is more CO2 due to no photosynthesis and continued respiration.

125
Q

what colour will hydrogen carbonate indicator go in a solution with light

A

purple/red because there is less CO2 due to it being used in photosynthesis and respiration.

126
Q

what colour will hydrogen carbonate indicator go in a solution with equal levels of resiration and photosyntheisis

A

pink because CO2 in = CO2 out

127
Q

name the two parts of the cell where most water is found

A

cytoplasm and vacuole

128
Q

how is the structure of the root hair cell adapted to absorb water from the soil

A

it has a large surface area and a permeable membrane

129
Q

what does boiling a leaf in water do

A

makes cell membranes permeable and prevent any starch digestion by denaturing enzymes

130
Q

how does adding boiling ethanol remove colour

A

it removes the chlorophyll as chlorophyll is soluble in ethanol

131
Q

what is the molecule that makes leaves green

A

chlorophyll

132
Q

what happens to a leaf when its destarched

A

the starch is removed

it is converted to glucose for respiration or energy

133
Q

what affects rate of photosynthesis

A

carbon dioxide conc
light intensity
temperature

134
Q

what is glucose converted to to be carried round the plant

A

sucrose

135
Q

what is glucose stored as

A

starch

136
Q

how do you start with a destarched plant

A

leave it in the dark for 24 hours

137
Q

what is the glucose made in photosynthesis used for

A 
sucrose for transport
starch for storage
cellulose for cell walls
proteins and DNA
lipids as an energy store in seeds
chlorophyll
138
Q

how would you show that photosynthesis is taking place in the presence of oxygen

A

use an aquatic plant, capture the gas produced and analyse it to show raised oxygen levels, or simply count the number of gas bubbles given off.

139
Q

why do plant cells need to be turgid

A

to support the plant

140
Q

what is transported by the xylem

A

water and mineral ions

141
Q

what is transported by the phloem

A

sucrose ans amino acids

142
Q

what is the xylem made up of

A

the cell walls of dead cells.

143
Q

what is the phloem made up of

A

Living cells.

144
Q

directional stimuli

A

they act in a particular direction

145
Q

what is a clinostat

A

a piece of apparatus consisting of an electric motor turning a cork disc. germinating seeds are attached to the disc, and the motor turns it so that the movement eliminates the effect of any directional stimulus that may be acting on the seeds.

146
Q

what can a clinostat be used to show

A

tropisms

147
Q

do plants produce gametes

A

no YES??

148
Q

do plants have fertilisation that takes place

A

no YES??

149
Q

do plants have genetic variation in their offspring

A

no

150
Q

what type of survival value do plant offspring have

A

only in a stable environment

151
Q

what type of survival value do animal offspring have

A

in a (stable and) changing environment

152
Q

what is a cutting

A

a form of plant reproduction, where a piece of a healthy plants stem with a few leaves attached is inserted into the soil. it will grow and develop into a new plant

153
Q

male gametes in a plant

A

pollen grains

154
Q

female gametes in a plant

A

egg/ova

155
Q

how are male gametes transferred to a females gametes in plants

A

pollination

156
Q

how is pollenation carried out in plants

A

wind or insects

157
Q

what does a plant zygote develop into

A

a seed which becomes enclosed in a fruit

158
Q

how are plant gametes produced

A

meiosis

159
Q

where are pollen grains produced

A

anthers of the stamens

160
Q

where are the eggs produced in a plant

A

ovules in the ocaries

161
Q

if pollen grains are transferred from the anthers of a flower to the stigma of the same plant what is it called

A

self-pollination.

162
Q

if pollen grains are transferred from the anthers of a flower to the stigma of a different plant what is it called

A

cross-pollination

163
Q

position of stamens in an insect-pollinated flower

A

enclosed within flower so that insect must make contact

164
Q

position of stigma in an insect-pollinated flower

A

enclosed within flower so that insect must make contact

165
Q

type of stigma in an insect-pollinated flower

A

sticky so pollen grains attach from insects

166
Q

size of petals in an insect-pollinated flower

A

large to attract insects

167
Q

colour of petals in an insect-pollinated flower

A

brightly coloured to attract insects

168
Q

nectaries in an insect-pollinated flower

A

present - they produce nectar, a sweet liquid containing sugars as a reward for insects

169
Q

pollen grains in an insect-pollinated flower

A

larger, sticky grains or grains with hooks to stick to insects bodies

170
Q

position of stamens in a wind-pollinated flower

A

exposed so that wind can easily blow pollen away

171
Q

position of stigma in a wind-pollinated flower

A

exposed to catch pollen blowing in the wind

172
Q

type of stigma in a wind-pollinated flower

A

feathery, to catch pollen grains blowing in the wind

173
Q

size of petals in a wind-pollinated flower

A

small

174
Q

colour of petals in a wind-pollinated flower

A

not brightly coloured, usually green

175
Q

nectaries in a wind-pollinated flower

A

absent

176
Q

pollen grains in a wind-pollinated flower

A

smaller, smooth, inflated grains to carry in the wind

177
Q

how does the nucleus of the pollen grain fuse with the nucelus of the ovum

A

the pollen grain forms a pollen tube, which grows down to through the tissue of the style and into the ovary. here it curves around to enter the opening in an ovule. the tip of the tube dissolves and allows the pollen grain nucleus to move out of the tube and into the ovule

178
Q

stages that lead the fertilised ovule to becoming a seed/fruit

A

zygote develops into an embryonic plant with a small root (radicle) and shoot (plumule)
other contents of the ovule evelop into a food store
ovule wall becomes the seed coat or testa
ovary wall becomes the fruit coat; this can take many forms depending on the type of fruit.

179
Q

germination

A

the food store is used up, providing the nutrients to allow the root (radicle) and shoot (plumule) to grow. the radicle grows downwards to get mineral ions and water, and the plumule grows up towards the light where it can start process of photosynthesis. once it can photosynthesise, germination is over.

180
Q

what conditions does germination require

A

warm temperatures for efficent enzymes
water for chemical reactions
oxygen for respiration

181
Q

practical investigating conditions needed for germination

A

4 tubes, A with wet cotton wool, B with dry cotton wool, C with oil and boiled water and D with wet cotton wool. they all contain seeds. A, B and C are maintained at room temp (20 degrees). D is placed in a refrigerator at 4 degrees. after a few days A will start to germinate. B and C will not. D will eventually.

182
Q

what do plants supply animals with

A

food, oxygen and they remove carbond dioxide

183
Q

when is photosynthesis carried out at a higher rate than respiration

A

when light intensity is high

184
Q

when is the only time a plant produces more carbon disoxide than it uses up

A

when it is in dim light

185
Q

describe carbon dioxide levels for a plant in bright light

A

there is an overall uptake of carbon dioxide from the air around a plant’s leaves, and a surplus production of oxygen that animals can use.

186
Q

when is carbon dioxide levels around plants highest

A

at night when no photosynthesis is occurring

187
Q

when is carbon dioxide around plants lowest

A

during the day when photoynthesis is happening at the highest rate

188
Q

what is hydrogen carbonate indicator used for

A

testing carbon dioxide conc

189
Q

what colour is hydrogen carbonate indicator in high conc of CO2 (>0.04%)

A

yellow

190
Q

what colour is hydrogen carbonate indicator in normal conc/air of CO2 (0.04%)

A

orange

191
Q

what colour is hydrogen carbonate indicator in low conc of CO2 (<0.04%)

A

purple

192
Q

which areas of a root hair cell are the main sites for water absorption

A

the root hairs (as they greatly increase SA)

193
Q

what is each hair of a root cell

A

a single, specialsied vell of the root epiermis.

194
Q

where is the water potential the highest in a root cell and its surroundings

A

in the soil.

195
Q

how do the roots absorb water from the soil

A

via osmosis as the soil has a higher water potential. water then moves out of the root hair cell to the outer tissue of the root (root cortex) and a gradient of water potential is set up, kept going by water being taken up the xylem in the middle of the root.

196
Q

pathway of water in the structure of the laf

A

up the xylem, in the leaf mesophyll. then evaporates into the air spaces between the spongy mesophyll cells. the water vapour then diffuses out through the stomatal pores.

197
Q

how is there a water potential gradient within the leaf

A

loss of water from the mesophyll draws water by osmosis from surrounding mesophyll cells. in turn, the xylem vessels supply the leaf mesophyll tissues with water.

198
Q

whatis the loss of water vapour from the leaves called.

A

transpiration

199
Q

what does transpiration cause

A

water to be pulled up the xylem in the stem and roots in a continuous flow known as the transpiration stream.

200
Q

functions of the transpirations stream

A

supplies water for the leaf cells to carry out photosynthesis
carries mineral ions dissolved in the water
provides water to keep the plant cells turgid
allows evaporation from the leaf surface, which cools the leaf, in a similar way to sweat cooling the human skin.

201
Q

why are there less stomata on the lower surface of leaves than upper

A

if they were mainly on the upper, the leaf would lose too much water. this is because the stomata would be exposed to direct sunlight, which would produce a high rate of evaporation from them. there is also less air movement on the underside of leaves.

202
Q

how do the guard cells open and close the stomata

A

during the day, water flows inside, and they swell up and become turgid. they bend outwards.

during the night, the guard cells become flaccid and lose this shape and the stoma closes.

203
Q

factors affecting rate of transpiration

A

light intensity
temperature
humidity
wind speed

204
Q

light intensity limiting factor

A

the rate of transpiration increases in the light, because of the opening of the stomata in the leaves, so that the leaf can photosynthesise.

205
Q

temperature limiting factor

A

high temperatures increase the rate of transpiration by increasing the rate of evaporation of water from the mesophyll cells.

206
Q

humidity limiting factor

A

when the air around the plant is humid, this reduces the diffusion gradient between the air spaces in the leaf and the external air. the rate of transpiration therefore decreases in humid air and speeds up in dry air

207
Q

wind speed limiting factor

A

the rate of transpiration increases with faster air movements across the surface of the leaf. the moving air removes any water vapour which might remain near the stomata. the moist air would otherwise reduce the diffusion gradient and slow down diffusion.

208
Q

what is a potometer

A

measures rate of transpiration or the rate if uptajke of water by a plant

209
Q

two types of potometers

A

weight

volume

210
Q

what does a weight potometer measure

A

the rate of loss of mass from a potted plant or leafy shoot over an extended period of time, ususally several hours.

211
Q

what does the polythyrene bag around the pot do

A

prevent loss of moisture by evaporation from the soil.

212
Q

what does the volume potometer do

A

magnifies the uptake in a capillary tube. the sumplest is a straight vertical tube joined to the shoot by a piece of rubber tubing.

213
Q

what are factors you could change when investigating effects of factors on the rate of transpiration using a simple potometer

A

using a fan or hair dryer to investifate the effect of moving air
placing the plant under a bright light to investigate the effect of changing light intensity

edexcel igcse biology (5 decks)

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