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Biology A level > Transportation in Plants > Flashcards

Transportation in Plants Flashcards

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1
Q

Why do plants require a transport system (metabolic demands)?

A

Glucose and oxygen made by photosynthesis, have to be transported to all cells

Waste needs to be removed

Hormones transferred

Mineral ions absorbed by root need to be transported for protein synthesis

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2
Q

Why do plants require a transport system (size)?

A

Actual plant can be very large, and doesn’t have Large SA:V ratio, so can’t totally rely on diffusion

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3
Q

What are dicotyledonous plants?

A

Have 2 halves to the seed called cotlyedons, which store nutrients for seed germination and to make the first leaves

Monocotyledonous plants on have one cotyledon

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4
Q

Examples of dicots?

A

Herbacous
Soft tissue, and short life span

Arborescent (woody)
Hard lignified tissue
Long life cycle

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5
Q

What’s the transport vessel in dicot roots?

A

Vascular system- Made up of xylem and phloem tissue

Arranged in vascular bundles, which are in middle to resist tugging strains

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6
Q

What’s the epidermis in a root?

A

Single layer of cells on outside of root

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7
Q

What’s a root hair?

A

Slender extension of a specialised epidermal cell, the root hair cell

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8
Q

What’s the xylem?

A

Centre of root, transports water and minerals

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9
Q

What’s the phloem?

A

Lies around xylem, transports sugars

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10
Q

What’s the endodermis?

A

Cylindrical layer of cells, encloses xylem and phloem

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11
Q

What’s the pericycle?

A

Just beneath endodermis, able to divide (meristem cells)

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12
Q

What’s the cortex?

A

Several layers of undifferentiated cells, between endodermis and epidermis

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13
Q

What are parenchyma cells?

A

Packing tissue, provides support walls permeable to water and dissolved solutes

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14
Q

How is the location of vascular bundles different in the stem, to the roots?

A

At edge of stem to provide support

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15
Q

What are the vascular bundles in young stems and non woody plants?

A

Seperate

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16
Q

What are the vascular bundles like in older woody stems?

A

Continuous vascular tissue

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17
Q

What are xylem vessels?

A

Long tubes, made up of columns of dead cells

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18
Q

How do xylem vessels become dead?

A

Initially elongated living cells

The cellulose cell walls become thickened with lignin, which is impermeable to water, so cell contents die

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19
Q

What are xylem vessels thickened with?

A

Lignin in spirals, so they don’t collapse under transpiration pull, also create pits

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20
Q

What do pits allow?

A

Water can pass sideways into other cells

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21
Q

What’s xylem parenchyma?

A

Packs around xylem vessels for support, stores food, and contains tannin-bitter tasting-protects plants

22
Q

What are xylem fibres?

A

Long cells with lignified secondary walls

Give extra mechanical strength

23
Q

What is sap?

A

Sugars dissolved in water

24
Q

What structures do phloem vessels contain?

A

Sieve tube elements

Companion cells

25
Q

What are sieve tube elements?

A

Living cells, lined up end to end to form sieve tube elements
Contain cross walls ie. sieve plates

26
Q

What happens as pores in sieve plate develop?

A

Tonoplast and many organelles break down, nucleus disappears

27
Q

Features of companion cells?

A

Small cells that lie between cell tubes

Provide metabolic processes for both companion and sieve tube

Plasmodesmata link sieve tube elements and companion cells

28
Q

Importance of water in plants:

A

Turgor pressure- supports plant, allows root to expand and push through soil

Loss of water via evaporation keeps plant cool

Mineral ions and products of photosynthesis transported in aqueos solution

Water is a raw material of photosynthesis

29
Q

Function of the root?

A

Anchors plant

Provides surface area for uptake of water from soil, increased by presence of root hairs

30
Q

Why does water move in to root hair via osmosis?

A

Low water potential in root hairs, due to solutes, high water potential in soil due to low concentration of mineral ions

31
Q

Describe the apoplast pathway?

A

Water moves through open network of fibres in cell walls with little resistance

32
Q

What forces allow water to flow continuously?

A

Joined by cohesive forces, creating tension

33
Q

Describe the symplast pathway?

A

Water moves through the cytoplasm from one cell to the next through plasmodesmata

So water moves via osmosis from one cell to the next until it reaches the endodermis

Each time water leaves a cell, the water potential decreases, maintaining the water potential gradient for the next water molecules to come into the cell

34
Q

What is the casparian strip?

A

Strip of wax in embedded in cell walls of endodermis, which is impermeable to water

35
Q

What happens at the casparian strip?

A

Blocks apoplast pathway, diverted across plasma membrane and into symplast pathway, so it has to travel across a ppm, preventing toxins spreading

36
Q

What’s the starch sheath?

A

Endodermis cells move minerals by active transport, from the cortex into the xylem
Water potential in xylem becomes more negative, water moves into xylem via osmosis

37
Q

What’s root pressure?

A

Positive hydrostatic pressure, pushing water up xylem

38
Q

Evidence of root pressure?

A

Cyanide which stops production of ATP, results in loss of root pressure
Lack of oxygen or respiratory substrates results in loss of root pressure

39
Q

What is translocation?

A

Movement of sucrose around the plant

40
Q

Why is sugar transported as sucrose?

A

Not used in metabolism, so less likely to be used along the way

41
Q

What’s the source?

A

Where the sugar starts

42
Q

Example of sources?

A

Green leaves
Storage organs eg. in roots
Food stores in seeds

43
Q

What’s a sink?

A

Where the sugar ends up

44
Q

Examples of sinks?

A

Growing roots

Parts of plant laying down food stores eg. roots or fruits

45
Q

What’s it called when sucrose gets from the source into the phloem?

A

Loading

46
Q

Symplast route for sucrose?

A

Sucrose moves from source into sieve tube elements via diffusion through plasmodesmata

47
Q

What is mass flow?

A

Hydrostatic pressure building up, and moves sucrose along

48
Q

Translocation for apoplast route?

A

Active process
Companion cells have proton pumps, which use ATP, to actively transport H+ ions out of cytoplasm into surrounding tissues
H+ diffusion gradient is set up
H+ ions diffuse back into companion cells via contransporter proteins, bringing sucrose back with them
Sucrose builds up, then diffuses across into sieve tube elements via plasmodesmata

49
Q

Why do companion cells have many infoldings in cell membrane?

A

Increase in surface area, more proton pumps and co transporter proteins, more movement of substances

50
Q

Why do companion cells have many mitochondria?

A

Lots of ATP produced for proton pumps

51
Q

How does sucrose move along phloem?

A 
Enters sieve tube
Water potential goes down
Water enters sieve tube by osmosis
Turgor pressure in sieve tube element goes up
Water flows from high pressure to low
52
Q

How is sucrose unloaded?

A

Sucrose molecules diffuse into active cells
Sucrose in plant cells is converted into starch or glucose
Sucrose concentration goes down
Concentration gradient maintained
Water potential in phloem goes up
Water follows sucrose into cells by osmosis
Hydrostatic pressure in phloem at sink is reduced

Biology A level (19 decks)

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