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Biology > Chapter 9- Transport In Plants > Flashcards

Chapter 9- Transport In Plants Flashcards

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1
Q

Define source and sink

A
  • source is where the assimilates are loaded into phloem

- sink is where the assimilates are unloaded from phloem

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2
Q

When bark removed from tree, phloem also removed. If complete ring of bark removed, tree trunk swells above the cut. Why?

A
  • sugar cannot pass out
  • cut causes infection
  • decreased water potential. Water moves into cells
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3
Q

Why lignin is essential in the wall of xylem vessels?

A
  • provides strength to prevent collapse of vessel because transpiration produces tension + water is under tension
  • to waterproof the vessel so cells die + contents decay to create hollow tube
  • improve adhesion of water molecules to reduce loss of water through wall
  • spiral pattern allows flexibility to prevent stem breaking
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4
Q

Why cartilage is essential in trachea?

A
  • to keep trachea open
  • provides strength to trachea to prevent collapse as during inhalation vol of lungs increases + lower pressure in thorax
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5
Q

Describe how cells are organised into tissues using xylem + phloem as examples.

A
  • xylem consists of vessels with no end walls + has function in transpiration stream
  • phloem has sieve tube elements + companion cells with many plasmodesmata. Important in translocation
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6
Q

Function of pits?

A
  • allow water to move in + out of xylem vessel

- to supply water to other parts of the plant

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7
Q

Parts of the leaf from which water may be lost?

A
  • stomata

- epidermis

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8
Q

How guard cells are adapted to their function?

A
  • unevenly thickened wall. Thick inner + thin outer walls
  • able to change shape
  • presence of mitochondria to provide ATP
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9
Q

Use cohesion- tension theory to explain how water molecules move from roots to leaves.

A
  • evaporation at top of plant
  • creates tension in xylem
  • water molecules stick together by H bonds
  • column pulled up by tension
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10
Q

H+ ions are moved out of the companion cells by?

A

Active transport

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11
Q

How do H+ ions + assimilates get cotransported back into companion cell?

A

Facilitated diffusion

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12
Q

What assimilates can be loaded?

A
  • sucrose

- amino acids

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13
Q

What evidence might scientists expect to see in companion cells to support phloem loading mechanism?

A
  • many mitochondria

- plasmodesmata between companion cells+ sieve tube

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14
Q

Distinguish between transpiration + transpiration stream

A
  • transpiration is the loss of water vapour by evaporation from a leaf
  • transpiration stream is the movement of water up xylem vessels from roots to leaves
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15
Q

Do xerophytes have hairs on their leaves?

A

Yes

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16
Q

Xylem vessels are impregnated with?

A

Lignin

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17
Q

Gaps in xylem vessel walls are called?

A

Pits

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18
Q

Gaps in cell walls between companion cells + sieve tube elements are called?

A

Plasmodesmata

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19
Q

Explain what happens to the air bubble in the capillary tube of a photometer as no. Of leaves increases?

A
  • as no. Of leaves increases, bubble movement increases
  • because there is a larger surface area + more stomata which results in more transpiration
  • thus, faster uptake of water by plants
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20
Q

-doing potometer investigation + not all leaves same. Why this may affect results + how to improve?

A
  • diff. No of stomata

- choose shoots with similar sized leaves

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21
Q

Assembles potometer underwater + leaves got wet. Why this may affect results + how to improve?

A
  • reduces water potential gradient between inside + outside of leaf
  • assemble with wetting leaves
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22
Q

Sun came out + lab warmed up. Why this may affect results + how to improve?

A
  • increased temp will increase transpiration

- carry out in room with controlled temp

23
Q

How active loading takes place?

A
  • active transport of H+ ions out of companion cells
  • this increases H+ ion conc + creates conc gradient
  • assimilates move with H+ ions down conc gradient through cotransporter protein by facilitated diffusion
  • sugar diffuses into sieve tube element through plasmodesmata
24
Q

Why as temp increases, the conc. of sugar found in phloem increases?

A
  • at low temp, molecules have little KE thus little ATP made. So less loading of sugars into sieve tube element
  • as temp increases, molecules have more KE thus more ATP made. So more loading of sugars into sieve tube element
  • at high temperatures, proteins denature
25
Q

Why rate of transpiration did not increase between light intensities 10 a.u + 20 a.u?

A

No extra stomata are opened

26
Q

Why transpiration is unavoidable during the day?

A
  • stomata are open to allow entry of CO2 for photosynthesis

- water vapour leaves the leaf down water vapour potential gradient

27
Q

How thick, waxy cuticles in a xerophyte reduce loss of water vapour?

A

-reduces evaporation through leaf epidermis

28
Q

How curled leaves in a xerophyte reduce loss of water vapour?

A

-traps water vapour + this reduces water potential gradient between inside + outside leaf

29
Q

How hairs in a xerophyte reduce loss of water vapour?

A

-traps water vapour. This reduces water potential gradient between inside + outside leaf

30
Q

Sugar most commonly translocated?

A

Sucrose

31
Q

Adaptations of sieve tubes?

A
  • elongated sieve tube elements
  • elements joined end to end to form column
  • sieve plates
  • little cytoplasm
  • few organelles
  • no nucleus
32
Q

Features of xylem that enable steam to pass from heated end of stem to cut end?

A
  • cells joined end to end with no end walls
  • pits in walls
  • hollow as no organelles
33
Q

Define transpiration

A

The loss of water vapour by evaporation from the leaf

34
Q

How transpiration contributes to the mechanism of water transport up the stem?

A
  • in leaf, water loss is replaced via apoplast pathway down water potential gradient by water from xylem in xylem vessel
  • loss of water causes low hydrostatic pressure at the top
  • water moves down pressure gradient under tension by mass flow which is due to the cohesion between water molecules
35
Q

Why bunch of flowers may survive longer if ends of stems removed immediately before flowers placed in water?

A
  • air in xylem removed

- restore continuous column of water in xylem

36
Q

Explain transpiration stream?

A
  • water vapour loss by evaporation at top of plant
  • water replaced via apoplast pathway from xylem down water potential gradient
  • this creates low hydrostatic pressure at top of xylem
  • high hydrostatic pressure at bottom of xylem
  • water, under tension, pulled up in continuous stream by mass flow
  • due to cohesion between water molecules bonded by H bonds
  • adhesion of water molecules to xylem
37
Q

Steps you should take when setting up potometer to ensure apparatus works properly?

A
  • apparatus should be air tight
  • leaves dry
  • shoot is healthy
  • assemble apparatus under water
  • cut end of shoot
38
Q

Why repeat experiment?

A
  • to help identify anomalies

- to make results more reliable

39
Q

Factors that decrease rate of transpiration?

A
  • lower temp
  • less light
  • more humid
  • less wind
40
Q

Why potometer only gives an estimate of the rate of transpiration?

A
  • potometer measures water uptake
  • not all water taken up is lost by evaporation
  • some water used in photosynthesis + making cells turgid
41
Q

Type of plant adapted to reduce water loss from leaves?

A

Xerophytes

42
Q

Adaptations of leaves that reduce evaporation?

A
  • hairy leaves: traps water vapour
  • sunken stomata: traps water vapour
  • rolled leaves: traps water vapour + reduces SA
  • thick waxy cuticle: reduces evaporation from epidermis
  • fewer stomata: less diffusion
43
Q

How water enters the endodermis?

A
  • ions enter against conc. gradient by active transport
  • this reduces water potential of endodermal cell
  • water moves by osmosis down water potential gradient
44
Q

Why leaf described as an organ?

A
  • organ is a collection of tissues working together to carry out a particular fucnction
  • leaves have epidermis, xylem, phloem

-for photsynthesis, gaseous exchange

45
Q

One molecule absorbed, how may be transported ot fruits?

A
  • in xylem by transpiration/ cohesion tension

- in phloem by translocation/ mass flow

46
Q

despite x being similar to nicotine, approved for use?

A

have little effect on humans

47
Q

Why both plants and animals need to be able to respond to changes in environment?

A
  • to avoid stress
  • to access resources
  • to avoid being eaten
48
Q

Describe the features of xylem that enable steam to pass from heated to cut end.

A
  • continuous as cells joined end to end

- no organelles

49
Q

Transpiration?

A

Transpiration is the loss of water vapour from a leaf via stomata

50
Q

How transpiration contributes to mechanism of water transport up stem?

A
  • in the leaf water loss is replaced via the symplast pathway down the water potential gradient by water from the xylem
  • in the xylem, this causes low hydrostatic pressure at top. Water moves from high pressure to low pressure down pressure gradient under tension by mass flow
51
Q

Why flowers may survive longer of ends of stems are removed immediately before placed in water?

A
  • to remove any air bubbles

- restore continuous column of water

52
Q

Why plant cells do not burst when they are in pure water?

A

-cell wall provides strength

53
Q

Why meristematic tissue need to be stained?

A
  • provide contrast between cell structures

- diff structures take up diff amounts of stain

54
Q

Where meristematic tissue can be found ?

A

Cambium
Tip of shoot
Tip of root

Biology (26 decks)

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