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Biology 9. Plants > Plants 9.1 Transportation in the xylem of plants > Flashcards

Plants 9.1 Transportation in the xylem of plants Flashcards

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1
Q

What is Transpiration

A

Transpiration is the loss of water vapour from the leaf/stomata as an inevitable consquence of gas exchange in the leaf

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2
Q

What is a primary organ of photosynthesis?

A

Plant leafs

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3
Q

What must be involved to sustain photosynthesis?

A

Exchange of two gases (CO2 and Oxygen as waste) as carbon dioxide is essential

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4
Q

What the problem with plants and their stomota?

A

if stomota allow carbon dioxide to be absorbed, they will also allow water vapour to escape

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5
Q

What is stomata?

A

These are pores in the epidermis

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6
Q

Why are stomata so important?

A

Because the waxy cuticles of plant leaves are not permeable (do not allow much water to pass through) pores are needed known as stomata

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7
Q

How do plants minimize water loss through the stoma?

A

Guard cells (on either side of a stoma)

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8
Q

What is the role of a guard cell?

A

Found in pairs, can controle the aperture of stoma and adjust from wide open to closed (to minimize water loss of leaf)

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9
Q

What is an exception of plants where stomata are not found?

A

liverworts

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10
Q

Why can gases not be exchanged on the surface of leafs without stomata?

A

the epidermis and waxy cuticle are impermeable to carbon dioxide and water

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11
Q

What causes a stoma to close?

A
  • water shortage, where the hormone absistic acid is produced, forcing closure to prevent dehydration
  • darkness
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12
Q

What happens to leaves in hot weather?

A

guard cells in the lower epidermis become flaccid which closes the stomata to prevent excessive water loss

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13
Q

What happens when leaves are well hydrated?

A
  • Guard cells remain turgid
  • Opens Stomata
  • water vapour diffuse out of leaf (transpiration)
  • carbon dioxide diffuses into the leaf (photosynthesis
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14
Q

What are xylem vessels?

A

Long/thin and hollow continues tubes in plants.

Their walls are contain cellulose and a polymer called lignin that makes them rigid, and able to withstand low pressures without collapsing.

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15
Q

How are xylem vessels formed?

A

files of cells where cell wall material is largely removed (most do not have plasma membrane)

Mature cells are nonliving so water movement is passive

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16
Q

Is pressure inside xylem vessels lower or higher than atmospheric?

A

Much lower pressure but does not collapse because of rigid structure

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17
Q

How can water be pulled up from the xylem in a continuous stream?

A

Cohesion

  • hydrogen bonds in water (polar intermolecular attraction) keep water molecules sticking together

Adhesion

  • water is attracted to hydrophilic parts of xylem

The connection between molecules pulls water up in continous stream

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18
Q

What does adhesion cause when water evaporates from surface of leaf?

A

Adhesion causes water to be drawn through cell wall from nearest available supply which is the xylem vessel (to replace water lost from evaporation)

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19
Q

What reduces pressure in the xylem?

A

When water is sucked out of the xylem even though pressure may already be low, but force of adhesion between water and cell walls are still strong enough

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20
Q

What is transpiration-pull?

A

A pulling force is generated by the low pressure that is transmitted through the water in the xylem vessels down the stem.

This is strong enough to move water upwards

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21
Q

What is cavitation?

A

When the liquid is unable to resist the low pressures in the xylem vessels and the column of liquid would break(it can even happen to water)

22
Q

How is water absorbed into root cells?

A

osmosis

  • solute concentration is higher inside root cell than in soil
23
Q

What are most solutes in root cells/soils?

A

Mineral ions

24
Q

How/Why does osmosis occur between root cells and soils?

A
  • concentration gradients of mineral ions between root cells and soils created by active transport
  • using protein pumps in plasma membranes of root cells
  • separate pumps for type of ion that plant requires (ions can only be absorbed with speicifc protein)
    *
25
Q

Why do some ions move through soils slowly?

A

ions bind to surface of soil particles

26
Q

How do overcome their slow movement through soil?

A

certain plants developed relationship with fungus

  • fungus grows on surface of roots (sometimes into cells)
  • the hyphae of gungus grow out into soil and absorb mineral ions from surface of soil
  • ions are then supplied to roots

allows plants to grow in mineral deficient soils

27
Q

What is an example of plant that recieves its mineral ions through fungus?

A

Heather family and orchids

28
Q

If fungus provides mineral ions to the plants, and plants provide sugars to the fungus, what is this relationship called?

A

mutalistic relationship

29
Q

Describe 3 ways in which terrestial plants support themselves

A
  • cellulose in cell wall around all plant cells (give strength, support and shape)
  • osmosis ensures all plants to be hydrated, creating turgor pressure
  • rings of lignin inside the xylm vessels provide strength
30
Q

What 3 factors can affect transpiration in terrestial plant?

A
  • light intensity
  • humidity
  • temperature
  • wind

all affect

31
Q

How can temperature affect transpirtion rate?

A
  • high temperature increases evaportation rate of water/transpiration
32
Q

How does humidity affect transpiration rate?

A

high humidity lowers the rate of water evaporation/transpirtation

33
Q

How does wind affect the transpiration rate?

A

air currents/wind increase water evaporation/transpiration

34
Q

How does light intensity affect transpiration?

A

usually increases photosynthesis/ water evaporation through stomata/transpiration

35
Q

What plant structures can reduce water loss?

A
  • thicker leaf cuticle
  • reduced surface area
  • rolled leave spines
  • reduced stomata
  • low growth form
  • C4 physiology
36
Q

How is water carried by transpiration stream?

A
  • transpiration is water loss (from plant) by evaporation;
  • flow of water through xylem from roots to leaves is the transpiration stream;
  • evaporation from spongy mesophyll cells;
  • replaced by osmosis from the xylem;
  • (diffusion of water vapour) through stomata;
  • water lost replaced from xylem / clear diagram showing movement of water from xylem through cell(s) (walls) to air space;
  • water pulled out of xylem creates suction/low pressure/tension; transpiration pull results;
  • water molecules stick together/are cohesive;
  • due to hydrogen bonding/polarity of water molecules;
  • xylem vessels are thin (hollow) tubes;
  • adhesion between water and xylem due to polarity of water molecules;
  • creates continuous column/transpiration stream;
37
Q

How does water evaporation occur in leaf? (4)

A
  • water evaporates in leaf through the stomata/transpiration
  • stomata open to allow gaseous exchange
  • abscisic acid stimulates closing of stomata
  • guard cells open/close the stomata
38
Q

How can water flow from root hair to xylem?

A
  • Apoplastic movement: water moves through cell walls
  • Symplast movement: water moves through cytoplasm
39
Q

How do plants achieve high surface area for water absorption?

A

Root hair cells possess root hair

40
Q

Outline the adaptions of plant roots for absorption of mineral ions from the soil

A
  • mineral ions are absorbed by active transport
  • large surface area
  • branching (increases surface area)
  • root hair
  • root hair cells have carrier protein/ion pumps (in plasma membrane)
  • many mitochondria in root hair cells
  • to provide ATP for transport
  • connections with fungi in the soil/fungal hyphae
41
Q

What are xerophytes?

A

Plants that are adapted to life in dry conditions

42
Q

What is an example of a xerophyte?

A

marram grass

43
Q

Outline adaptions xerophytes

A
  • reduced leaves/spines to prevent water loss (eg. Cacti)
  • rolled leaves/spines to prevent water loss
  • stomata on inside/sunken stomata
  • thick waxy cuticle/hairs on leaves (hair slows air movement)
  • reduced stomata to prevent water loss
  • deep wide spread roots to obtain more water
  • special tissue for storing water
  • take in CO2 at night (stored as malic acid)
44
Q

How can cacti perfom photosynthesis even when their stomata is closed?

A
  • They absorb CO2 over night and store it as malic acid
  • this is then released during the day to allow CO2 to occur even with closed stomata

called Cassulacean acid metabolism

Plants that use this are called CAM plants

45
Q

What are saline soils?

A

High salt concentrated soils

46
Q

What are plants called that live in saline soils?

A

halophytes

47
Q

What adaptions do halophytes have for water conservation?

A
  • leaves are reduced to small scaly structures/spines
  • leaves are shed when water is scarce
    • stems become green and take over function of photosynthesis when leaves are not present
  • water storage structures develop in leaves
  • thick cuticle and multiple layered apidermis
  • sunken stomata
  • long roots
  • structures to remove salt build-up
48
Q

Draw a primary xylem vessels in section of a stem based on this

A
  • xylem
  • phloem
  • cambium
  • vascular bundle
  • epidermis
  • cortex
  • pith
49
Q

Describe structure of primary xylem vessel

A
  • thin primary wall that is unlignified and permeable
  • lignified secondary thickening (usually helical or annular)
  • thickening allows contunues growth as
    • rings of annular thickening can move apart
    • helical thickening can be stretched
50
Q

When is secondary xylem produced?

A

When extension growth is complete

51
Q

How is secondary xylem different from primary?

A
  • more extensively lignified
  • thickening provides more strength but no growth

Biology 9. Plants (6 decks)

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