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biology > plant physiology > Flashcards

plant physiology Flashcards

1
Q

properties of starch

A

insoluble, compact, easily broken down

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2
Q

testing leaves for starch practical

A
  • remove leaf from plant that has been in light for several hours prior
  • place in boiling water for 30 seconds to kill it and remove the wax
  • place in boiling tube containing ethanol and place this in a beaker containing boiling hot water which will boil the ethanol for a few mins until it cools, since ethanol (78) has a lower boiling point than water (100)
  • this decolourises the leaf
  • wash with cold water then spread out on tile and add a few drops of iodine solution
  • part of the leaf with starch will turn blue-black
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3
Q

starch is only made in

A

the parts of plants that contain chlorophyll

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4
Q

starch production in leaves needs

A
  • light
  • carbon dioxide
  • chlorophyll
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5
Q

how starch is produced in plants

A

first plants produce glucose which is then joined together in chains to form starch

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6
Q

photosynthesis

A

process carried out in organisms containing chlorophyll. light energy is used to drive reactions where carbon dioxide and water are used to make glucose and oxygen

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7
Q

photosynthesis equation

A

carbon dioxide + water –> glucose + oxygen

6CO2 + 6H20 –> C6H12O6 + 6O2

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8
Q

what is photosynthesis the conversion of

A

photosynthesis is the conversion of light energy into chemical energy

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9
Q

the structure of a leaf

A

the upper and lower epidermis contain few chloroplasts and are covered by a thin waxy material called the cuticle- which reduces water loss by evaporation and acts as a barrier against disease-causing microorganisms e.g bacteria and fungi

the lower epidermis contains many little pores called stomata, the upper epidermis contains few or none. Stomata are formed as gaps between two highly specialised cells called guard cells which change their shape to open or close the stoma.

the mesophyll is made up of two layers of cells known as the palisade mesophyll and spongy mesophyll

the palisade mesophyll consists of long, narrow-shaped cells containing hundreds of chloroplasts. These are close to the source of light and since the upper epidermis is relatively transparent, this means that the light is able to reach the chloroplasts in the cell

the spongy mesophyll consists of rounded, loosely-packed cells with air spaces between them. it has fewer chloroplasts but still photosynthesises this is the main gas exchange surface of the leaf, it absorbs CO2 and releases water vapour and oxygen. the air spaces allow gases to diffuse in and out of the mesophyll.

the xylem and phloem make up the vascular bundle. xylem supplies the leaf with water and mineral ions. phloem carries the products of photosynthesis such as sugars away from the mesophyll. It transports the products to other parts of the plant that cannot make their own food.

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10
Q

effect of increasing light intensity on photosynthesis and respiration

A

means higher rate of photosynthesis than respiration which means there is a higher uptake of carbon dioxide than released

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11
Q

hydrogen carbonate indicator experiment (effect of light intensity on photosynthesis)

A
  • 4 tubes
  • observe change of color
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12
Q

explaining how starch is needed for photosynthesis

A
  • chlorophyll= variegated leaf experiment
  • CO2= soda lime experiment
  • light= plant in darkness for 48 hours

all test negative for starch, shows that starch is needed for photosynthesis

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13
Q

how leaves are adapted for photosynthesis

A
  • large SA to absorbs sunlight
  • upper epidermis is relatively transparent
  • palisade cells which contain many chloroplasts are close to the top of the plant and therefore the light source
  • stomata allow CO2 to diffuse directly into the leaf
  • large network of vascular bundles
  • waxy cuticles reduce water loss + act as a barrier
  • spongy mesophyll has air spaces to allow diffusion
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14
Q

limiting factors on the rate of photosynthesis

A

light intensity, concentration of CO2, temperature

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15
Q

canadian pondweed experiment

A
  • sodium hydrogen carbonate is added to water in the boiling tube (solution produces Co2)
  • measures the oxygen produced from photosynthesis in plants
  • gas syringe
  • water bath
  • light source
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16
Q

uses of glucose in plants

A
  • sucrose for transports (phloem)
  • respiration
  • cellulose for cell wall
  • chlorophyll
  • lipids for membranes and energy
  • proteins + DNA
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17
Q

uses of nitrate

A

makes amino acids, proteins, chlorophyll, DNA

deficiency: limited growth, older leaves turn yellow

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18
Q

uses of phosphate

A

contains phosphorous for making DNA and cell membranes

deficiency: poor root growth, younger leaves turn purple

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19
Q

uses of potassium

A

needed for enzymes of photosynthesis and respiration

deficiency: discoloured leaves, poor flower and fruit growth

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20
Q

uses of magnesium

A

part of chlorophyll molecule

deficiency: leaves turn yellow

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21
Q

osmosis

A

net diffusion of water molecules across a partially permeable membrane from a solution with higher water potential to a solution with a lower water potential

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22
Q

cell placed in dilute solution or water

A

cell placed in dilute solution or water absorbs water by osmosis and becomes turgid

23
Q

cell placed in concentrated solution

A

cell placed in concentrated solution loses water by osmosis and becomes flaccid

24
Q

excessive water loss in cells

A

excessive water loss in cells by osmosis causes the cell to become plasmolysed

25
Q

importance of turgor in plants

A
  • supports young stems and leaves of a plant, holds the stem upright so the leaves can carry out photosynthesis properly
  • important in the functioning of the stomata
26
Q

onion epidermis cells practical

A

onion epidermis cells placed on slides:

1 with water
2 with concentrated sucrose solution

observed under microscope: water one becomes turgid, sucrose one becomes flaccid

27
Q

potato tuber tissue practical

A
  • potato chips cut into 5 x 1 x 1cm, excess moisture removed, and weighed
  • 3 boiling tubes: 1 with water, 2 with concentrated sucrose solution, 3 empty
  • potato chip placed in each one for 30 mins
  • remove excess liquid and re-weigh, felt to compare stiffness and flexibility
  • calculate % change in mass
28
Q

uptake of water by roots

A
  • roots are covered in thousands of tiny root hairs which gives the root a larger surface area
  • each hair has a long, thin outer projection which penetrates between soil particles
  • water in soil has a lower concentration of solutes than inside the root hair cell
  • water in soil has a higher water potential so water moves inside cells by osmosis
  • water is taken up by root hairs and carried across the root cortex by a water potential gradient
  • water enters the xylem and is transported to all parts of the plant
29
Q

transpiration

A

loss of water vapour from the leaves of plants

30
Q

transpiration stream

A
  • water leaves mesophyll and evaporates in the air spaces, water vapour diffuses out of the leaf through the stomata
  • this loss of water, known as transpiration, creates a water potential gradient which causes water to be ‘pulled up’ the xylem in the stem and from the roots which creates a continuous flow known as the transpiration stream
31
Q

functions of the transpiration stream

A
  • supplies water for the leaf cells to carry out photosynthesis
  • carries mineral ions dissolved in the water
  • provides water to keep the cells turgid
  • allows evaporation from the leaf surface
32
Q

control of transpiration by the stomata

A

in light, water enters the guard cells by osmosis causing them to become turgid, this opens the stomata

in darkness, water leaves the guard cells by osmosis causing them to become flaccid, this closes the stomata

33
Q

transport in the xylem

A
  • xylem is made of dead cells with a hollow lumen, walls are strengthened using lignin
  • one way transport, supplies water and minerals to the plant.
  • involves the transpiration stream: water evaporates in the air spaces in the mesophyll and diffuses out of the leaf as water vapour through the stomata so water is ‘pulled up’ from the roots of the plant through the xylem because of osmosis to replace it thus forming a continuous flow known as the transpiration stream.
34
Q

transport in the phloem

A
  • transports the products of photosynthesis to all parts of the leaf and to parts that cannot make their own food, e.g sugar for respiration and amino acids for growth
  • movement in the phloem is known as translocation (travels up and down)
  • has sieve plates which allow the movement of food
  • companion cells which have mitochondria for energy transfer, energy is used to move the food in the phloem
  • sucrose is loaded into the phloem through active transport (against the concentration gradient, energy required, active process)
  • water moves into the phloem by osmosis
35
Q

potometer experiment

A

estimates transpiration rates by measuring the water uptake of a plant

  • cut a shoot underwater so that no air enters the xylem, cut it at a slant to increase its surface area
  • assemble the potometer in water and insert the shoot underwater so no air can enter
  • remove the apparatus from the water but keep the end of the capillary tube submerged in a beaker of water
  • check that apparatus is watertight and airtight
  • dry leaves, let shoot acclimatise
  • remove the end of the capillary tube from the beaker allowing one air bubble to form and then submerge it again
  • record the starting position of the bubble using a ruler
  • start the stopwatch and record the distance moved by the bubble per unit time
  • keep conditions e.g temp and humidity constant
36
Q

environmental conditions affecting transpiration rates

A
  • light intensity: increasing light intensity means that more stomata are open for photosynthesis so more water vapour is lost, meaning more transpiration
  • temp: higher temp means particles move faster meaning more water particles will evaporate from the leaf, so transpiration increases
  • wind speed: as wind speed increases it moves away the water particles in the air surrounding the leaf which increases the diffusion gradient in comparison to inside the leaf, this increases the rate of transpiration
  • humidity: the more humid the air is, the more water in it which reduces the concentration gradient between inside and outside the leaf, slowing down the rate of transpiration, therefore transpiration decreases as humidity increases.
37
Q

tropism

A

growth of a plant in response to a directional stimulus

38
Q

types of tropism

A
  • positive phototropism
  • negative phototropism
  • positive geotropism
  • negative geotropism
39
Q

coleoptile

A

protective sheath that covers the first leaves of a cereal seedling

40
Q

auxin

A

plant hormone that diffuses from the tip of the shoot downwards, it causes cell elongation and division.

in light it diffuses towards the shaded area

41
Q

asexual reproduction

A

no fusion of gametes, produced by an organism separating from a single parent

42
Q

sexual reproduction

A

reproduction involving the fusion of male and female gametes to form a zygote

43
Q

sexual vs asexual reproduction

A
  • production of gametes: yes, no
  • fertilisation takes place: yes, no
  • genetic variation in offspring: yes, no
  • has survival value in: changing environment, stable environment
44
Q

methods of asexual reproduction

A

natural: runner: new plant is produced where runners touch the ground

artificial: cuttings: piece of plants stem with some leaves attached is cut off from a healthy plant, and planted to develop into a new plant

45
Q

two types of pollination

A

wind or insect

46
Q

sexual reproduction in plants

A

male gamete=pollen grains, female gamete=ova. Male gamete must be transferred to female gamete through pollination, either by wind or insect. then, fertilisation takes place and the zygote formed develops into a seed and becomes enclosed in a fruit.

47
Q

production of gametes

A

gametes are produced by meiosis in the structure of the flowers. male gametes are produced in the anthers in the stamen. female gametes are produced in the ovules in the ovaries.

48
Q

pollination process

A

pollen grains are transferred from the anthers of a flower to the stigma, if this occurs in the same flower this is called self-pollination. if this occurs between two different flowers, this is known as cross-pollination.

49
Q

difference in the structure between insect-pollinated flowers and wind-pollinated flowers

A
  • position of stamens: enclosed in the flower so that the insect must make contact vs. exposed so that the wind can easily blow pollen away
  • position of stigma: enclosed in the flower so that the insect must make contact vs. exposed to catch the pollen blowing in the wind
  • type of stigma: sticky so that pollen grains attach vs. feathery to catch pollen grains blowing in the wind
  • size of petal: large to attract insects vs. small
  • colour of petal: bright to attract insects vs. not bright, usually green
  • nectaries: produce a sweet liquid known as nectar to ‘reward’ insects vs. no nectaries
  • pollen grains: larger, sticky grains to stick to insects’ bodies vs. smaller smoother, inflated grains to carry in the wind
50
Q

fertilisation

A

pollen grain attaches to the stigma of the flower, the male and female gamete must fuse so the pollen grain develops into a pollen tube that grows down the style until it reaches the ovaries where the tip dissolves which allows the pollen grain nucleus to move into the ovule where it fertilises the ovum nucleus, forming a zygote.

51
Q

seed and fruit formation

A
  • zygote develops into an embryonic plant with small root and shoot
  • other contents of the ovule develop into a food store fro the young plant when the seed germinates
  • the ovule wall becomes the seed coat
  • the ovary wall becomes the fruit coat
52
Q

germination

A

during germination the food store in the cotyledons or other part of the seed is used up, providing the nutrients to allow the radicle (root) and plumule (shoot) to grow. the radicle grows down into the soil, where it will absorb water and mineral ions. the plumule grows upwards towards the light, where it can start the process of photosynthesis. once the seedling is able to photosynthesise, germination is over

53
Q

conditions required for germination to take place

A
  • warm temperature so that enzymes can act efficiently
  • water for chemical reactions to take place in solution
  • oxygen for respiration

biology (9 decks)

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