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Biology > Topic 9 > Flashcards

Topic 9 Flashcards

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1
Q

Sieve elements

A

sieve elements form tubes which transport water & solutes

- to be efficient at transport, they have reduced quantities of the cytoplasm and have no nucleus, ribosomes or vacuole

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2
Q

Fibres of Sclerenchyma cells

A

provide structural support for the plant

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3
Q

Paranchyma

A

acts as a packaging material between other cell types & helps transfer materials to the sieve elements & companion cells

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4
Q

Companion cells

A

are “life support” for the sieve element cells as they perform certain metabolic functions for sieve elements
- also why plasmodesmata(microscopic pores in the cell walls) between companion cells & sieve element cells are larger than in most plant cells to allow for the exchange of metabolites (e.g ATP)

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5
Q

How are sieve tubes structured to its function?

A
  • Rigid cell walls of sieve tube
    → allow for the building of high pressures needed to generate hydrostatic pressure (the flow inside the tubes)
  • The ends of sieve element cells are connected with other sieve elements together to form a sieve tube
  • Sieve plates are found
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6
Q

What is hydrostatic pressure?

A

the pressure exerted by a liquid due to the force of gravity

- in the phloem it causes the sugar & the water to be pushed towards the source cell (translocation)

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7
Q

What are the functions of transpiration?

A
  • carries water to various parts of the plant
  • carries minerals along w the water
  • cools down the plant when water evaporates through the stomata
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8
Q

cuticle

A
  • protects the plant against water loss & insects
  • if no cuticle is present, the epidermis protects the leaf
  • waxy, so its good for water loss prevention
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9
Q

Epidermis

A
  • provides a protective barrier if no cuticle is present

- flat, tightly packaged cells on the leaf

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10
Q

Palisade mesophyll

A
  • cells that are near the top of the leaf that are most responsible for light absorption & photosynthesis (why they are at the top & not the bottom)
  • contain a lot of chloroplast (bc thats what’s needed for photosynthesis)
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11
Q

Spongy mesophyll

A
  • a layer of sparsely spaced cells where there are channels for gas exchange
  • air pockets allow for efficient gas exchange ->the gases that are coming in & out of the cell are oxygen & carbon dioxide
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12
Q

What is the rate of transpiration in xerophytes & why?

A

Xerophytes will have high rates of transpiration due to the high temperatures and low humidity of desert environments

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13
Q

What are xerophytes?

A

Xerophytes are plants that can tolerate dry conditions (such as deserts) due to the presence of a number of adaptations

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14
Q

What are the adaptions of xerophytes?

A
  • Reduced leaves
  • rolled leaves
  • thick, waxy cuticle
  • stomata in pits
  • low growth
  • CAM physiology
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15
Q

What are halophytes?

A

Halophytes are plants that can tolerate salty conditions (such as marshlands) due to the presence of a number of adaptations

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16
Q

What are the adaptions of halophytes?

A
  • Cellular sequestration
  • Tissue partitioning
  • root level exclusion
  • salt excretion
  • altered flowering schedule
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17
Q

What is a photometer?

A

a device that is used to estimate transpiration rates by measuring the rate of water loss / uptake

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18
Q

What are the models of water transport?

A
  • capillary tubing
  • filter paper
  • porous pots
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19
Q

Capillary tubing

A
  • Water has the capacity to flow along narrow spaces in opposition to external forces like gravity (capillary action)
  • This is due to a combination of surface tension (cohesive forces) and adhesion with the walls of the tube surface
  • The thinner the tube or the less dense the fluid, the higher the liquid will rise (xylem vessels are thin: 20 – 200 µm)
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20
Q

Filter paper

A
  • Filter paper (or blotting paper) will absorb water due to both adhesive and cohesive properties
  • When placed perpendicular to a water source, the water will hence rise up along the length of the paper
  • This is comparable to the movement of water up a xylem (the paper and the xylem wall are both composed of cellulose)
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21
Q

Porous pots

A
  • Porous pots are semi-permeable containers that allow for the free passage of certain small materials through pores
  • The loss of water from the pot is similar to the evaporative water loss that occurs in the leaves of plants
  • If the porous pot is attached by an airtight seal to a tube, the water loss creates a negative pressure that draws more liquid
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22
Q

What is translocation?

A

is the movement of organic compounds (e.g. sugars, amino acids) from sources to sinks

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23
Q

What is a source?

A

a source is where organic compounds are synthesised - this is the photosynthetic tissue (e.g leaves)

24
Q

What is the sink?

A

the sink is where the compounds are delivered to for use or storage - this includes roots, fruits & seeds

25
Q

Why are sugars transported as a disaccharide?

A

transported as sucrose bc it is soluble but metabolically inert

26
Q

What are aphids?

A

are a group of insects, belonging to the order Hemiptera, which feed primarily on sap extracted from phloem

27
Q

What are the factors affecting translocation rate?

A
  • the rate of photosynthesis
  • the rate of cellular respiration
  • the rate of transpiration
  • the diameter of the sieve tubes
28
Q

What are meristems?

A

Meristems are tissues in a plant consisting of undifferentiated cells capable of indeterminate growth

29
Q

What is micropropagation?

A

Micropropagation is a technique used to produce large numbers of identical plants (clones) from a selected stock plant

30
Q

Micropropagation is used to rapidly produce large numbers of cloned plants under controlled conditions:

A
  • rapid bulking
  • virus free strains
  • propagation of rare species
31
Q

Rapid Bulking

A
  • Desirable stock plants can be cloned via micropropagation to conserve the fidelity of the selected characteristic
  • This process is more reliable that selective breeding because new plants are genetically identical to the stock plant
  • This technique is also used to rapidly produce large quantities of plants created via genetic modification
32
Q

Virus-free strains

A
  • Plant viruses have the potential to decimate crops, crippling economies and leading to famine
  • Viruses typically spread through infected plants via the vascular tissue – which meristems do not contain
  • Propagating plants from the non-infected meristems allows for the rapid reproduction of virus-free plant strains
33
Q

Propagation of Rare Species

A
  • Micropropagation is commonly used to increase numbers of rare or endangered plant species
  • It is also used to increase numbers of species that are difficult to breed sexually (e.g. orchids)
  • It may also be used to increase numbers of plant species that are commercially in demand
34
Q

What is pollination?

A
  • The transfer of pollen grains from an anther (male plant structure) to a stigma (female plant structure)
35
Q

What is fertilisation?

A
  • Fusion of a male gamete nuclei with a female gamete nuclei to form a zygote
36
Q

What is seed dispersal?

A
  • Fertilisation of gametes results in the formation of a seed, which moves away from the parental plant
37
Q

What is the stamen composed of?

A
  • anther

- filament

38
Q

What is the pistil (or carpel) composed of?

A
  • stigma
  • style
  • ovule
39
Q

Anther

A
  • pollen producing organ of the flower (pollen is the male gamete of a flowering plant)
40
Q

Filament

A
  • slender stalk supporting the anther (makes the anther accessible to pollinators)
41
Q

Stigma

A
  • the sticky, receptive tip of the pistil that is responsible for catching the pollen
42
Q

Style

A

the tube-shaped connection between the stigma and ovule (it elevates the stigma to help catch pollen)

43
Q

Ovule

A

the structure that contains the female reproductive cells (after fertilisation, it will develop into a seed)

44
Q

Petals

A

function to attract pollinators

45
Q

Sepal

A

Outer covering which protects the flower when in bud

46
Q

What are phytochromes?

A

Phytochromes are leaf pigments which are used by the plant to detect periods of light and darkness

47
Q

What is photoperiodism?

A

The response of the plant to the relative lengths of light and darkness

48
Q

Phytochromes exist in two forms – an active form and an inactive form:

A
  • The inactive form of phytochrome (Pr) is converted into the active form when it absorbs red light (~660 nm)
  • The active form of phytochrome (Pfr) is broken down into the inactive form when it absorbs far red light (~725 nm)

Additionally, the active form will gradually revert to the inactive form in the absence of light (darkness reversion)

49
Q

Why is the active form predominant during the day?

A

Because sunlight contains more red light than moonlight, the active form is predominant during the day
- Similarly, as the active form is reverted in darkness, the inactive form is predominant during the night

50
Q

What will a typical seed possess?

A
  • testa
  • micropyle
  • cotyledon
  • plumule
  • radicle
51
Q

Testa

A

an outer seed coat that protects the embryonic plant

52
Q

Micropyle

A

a small pore in the outer covering seed, that allows for the passage of water

53
Q

Cotyledon

A

contains the food stores for the seed and forms the embryonic leaves

54
Q

Plumule

A

the embryonic shoot (also called the epicotyl)

55
Q

radicale

A

the embryonic root

56
Q

For germination to occur, a seed requires a combination of:

A
  • oxygen
  • temp
  • water
  • pH
57
Q

How can germination be measured?

A

germination can be measured by the rate of seed growth over a set period of time

Biology (28 decks)

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