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Biology Year 12 > Plant Transport ✅ > Flashcards

Plant Transport ✅ Flashcards

1
Q

What are the key functions of water

A

Photosynthesis
Structure/ turgidy
Transport/ solvent
Thermo regulation
Site of chemical reactions

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2
Q

Definition of xerophytes

A

A species of plant that has adaptions to survive in an environment with little liquid water

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3
Q

What is definition of hydrophytes

A

A plant which grows only in or on water

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4
Q

What adaptions do hydrophytes have, what are the benefits of them

A

No waxy cuticle, cuticle serves little purpose in hydrophytes because water loss not an issue

Stomata located on upper leaf features, gas exchange is maximized

Reduction in internal structural support, unnecessary feature because water can support aquatic plants

Air sacs + Aerenchyma, increased buoyancy; leaves and flowers can float on water surface

Small roots, water uptake via roots less significant because water can diffuse directly into other parts of submerged plants

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5
Q

What is the Need for Transport Systems in Plants

A

All living organisms have the need to exchange substances with their surrounding environment
Plants need to take carbon dioxide and nutrients in
Waste products generated need to be released

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6
Q

What is an exchange site

A

The location within an organism where exchange occurs

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7
Q

How can small organisms exchange substances directly with the environment
Eg Chlamydomonas

A

large surface area: volume ratio
The diffusion or transport distance in these organisms are also very small so essential nutrients or molecules are able to reach the necessary parts of the cell efficiently
Smaller organisms have lower levels of activity and so smaller metabolic demands

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8
Q

Why do larger organisms require specialised mass transport systems

A

Increasing transport distances

Surface area: volume ratio

Increasing levels of activity

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9
Q

What are some adaptations present in plants that help to increase their SA: V ratio

A

Plants have a branching body shape
Leaves are flat and thin
Roots have root hairs

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10
Q

Why is the demand for oxygen and nutrients is greater and more waste is produced is larger organisms

A

A larger number of cells results in a higher level of metabolic activity

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11
Q

What is mass flow

A

the bulk movement of materials. It is directed movement so involves some source of force

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12
Q

Mass transport systems help to…

A

Bring substances quickly from one exchange site to another

Maintain the diffusion gradients at exchange sites and between cells and their fluid surroundings

Ensure effective cell activity by keeping the immediate fluid environment of cells within a suitable metabolic range

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13
Q

What does xylem transport and is it alive or dead

A

Water and mineral ions, dead

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14
Q

What does phloem transport and is it alive or dead

A

Sucrose and other nutrients, alive

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15
Q

Why do plants not have a specialized transport system

A

They have adaptations that give them a high SA: V ratio for the absorption and diffusion of gases

The leaves and stems possess chloroplasts which produce oxygen and use up carbon dioxide

There is a low demand for oxygen due to plant tissues having a low metabolic rate

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16
Q

Need to know arrangements of roots, stem and leave’s vascular tissue

A

Know it

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17
Q

How do xylem cells key features work

A

Dead cells fused to form hollow vessels, strengthened by lignin

Pits in xylem wall enable water to move our into adjacent xylem vessels or other cells

Xylem Fibres add strength, xylem parenchyma cells store food

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18
Q

What is the function of xylem cells

A

Transport of water and minerals up a plant

Tissue also provides structural support for plant

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19
Q

How do phloem key features work

A

Sieve tube elements are living cells joined end-to-end, forming a tube with internal pores (sieve plates)

Companion cells carry out all metabolic functions of phloem tissue (lacks nuclei). Materials pass into siege tubes via plasmodesmata (cell wall channel)

20
Q

What is the function of phloem cells

A

Transport of solutes (eg sugars and amino acids) up and down a plant

21
Q

Describe the different arrangement of vascular tissue in roots and stems (2 marks)

A

Central in roots;
Towards the outside of stems

22
Q

Outline how could vessels are adapted for water transport (3 marks)

A

Lignin strengthens the vessels;
No end wall, which enables a smooth flow of water;
Pits enable water movement between vessels

23
Q

Explain how sieve tube elements survive, despite lacking nuclei and containing a small amount of cytoplasm

A

Companion cells carry out the functions that the sieve tube elements cannot

Communication between the 2 types of cell occurs through plasmodesmata

24
Q

How are root hair cells adapted to take up water from the surrounding soil

A

Long and narrow, which increases SA:V ratio

Able to penetrate between soil particles

Able to maintain a water potential gradient between soil and the cell (due to solutes dissolved in the root)

25
Q

How does water move into root hair cells

A

Osmosis

26
Q

how does water enter the xylem

A

Water reaches the endodermis surround xylem vessels. The Casparian strip around the endodermal cells forces water in the apoplast pathway into cytoplasm

Endodermal cells move mineral ions into xylem by active transport. Water potential in endodermal cells is higher than xylem. Water diffuses into xylem by osmosis. Root pressure helps initial flow into vascular tissue and helps to force water up stem

27
Q

What are the 2 movements of water form cell to cell towards the xylem

A

Apoplast pathway= through cell walls

Symplast= through the cytoplasm

28
Q

State 2 uses of water in plants (2
Marks)

A

Maintaining turgor [1]
For photosynthesis [1]
Transport medium [1]
Cooking plants via evaporation [1]

29
Q

Describe and explain the function of the casparian strip (3 marks)

A

Forces water back into cytoplasm/ Symplast pathway [1]
Because the strip is waterproof [1]
Prevents water returning from xylem to Cortex [1]

30
Q

Compare and contrast the movement of water through the apoplast and Symplast pathways (5 marks)

A

Apoplast: water mover through cell walls [1]
And intercellular spaces [1]
Symplast: water moves through cytoplasm [1]
And plasmodesmata [1]
Water experiences little resistance in the apoplast pathway [1]

31
Q

What is transpiration

A

The evaporation of water from a plants leaves (water evaporates from cells inside the leaves and diffuses out of the stomata)

32
Q

Explain transpiration and water movement through xylem

A

Water leaves plant by transportation (through stomata)

Water pulled up through xylem vessels to replace water lost through transpiration (transpiration pull)

Water molecules cohere to each other (attract) through H2 bonding (exhibit cohesion), this enables an unbroken chain of water moly to be pulled up the xylem vessels (transpiration stream)

Water molecules adhere to sides of xylem vessels, this helps the transpiration stream up the narrow vessels (capillary action)

33
Q

What is the evidence for cohesion-tension theory

A

Tress become narrower when they transpire (increased tension in xylem vessels during high rates of transpiration )

Air is sucked up rather then water leaking out when a stem is cut

Water no longer moved up broken stem because air pulled in breaks transpiration stream

34
Q

List environmental factors that effect transpiration rate

A

Light intensity: stomata open in the light, higher light increases T rate

Temperature: changes kinetic energy of molecules, high temp increases T rate

Humidity: affect the water potential gradient between leaf and air, lower humidity increase T rate

Air movement: affects how quickly moist air is removed, more air movement increases T rate

35
Q

List factors within a plant that affects transpiration rate

A

Number of leaves: affects the SA available for loss of water vapor, more leaves increases T rate

Number of stomata: alters how much water is able to diffuse from the leaves, more (and larger) stomata increases T rate

Thickness of cuticle: waxy cuticle reduce water loss, thin (or no) cuticles increases T rate

36
Q

Describe how to do measuring transpiration practical

A

Fresh shoot: stem is cut under water and transferred to the apparatus to avoid introducing air bubbles to the stem- but carw must be taken not to get water into the leaves
A reservoir from which water can be let into capillary tube, pushing the air bubble back to the start of the scale

Scale calibrated in cm to measure distance air bubble moves along tube as water is absorbed by shoot

Rate calculated by distance moved by air bubble after a set time

37
Q

State how each of the following conditions would affect transpiration rate:
A: decreased temp
B: increased light intensity
C: absence of waxy cuticle (6marks)

A

A: lower rate[1], reduced kinetic energy of water molecules [1]
B: higher rate[1], more stomata open [1]
C: higher rate [1], leaves are more permeable [1]

38
Q

Explain why number of stomata in a leaf is likely to represent a compromise that depends on environmental conditions in a plants habitat (2 marks)

A

Stomata required for gas exchange [1]
But water loss when stomata are open [1]

39
Q

Assimilates are translocated from sources to sinks, what are some examples of sources and sinks

A

Sources include: green leaves and stems, and storage sites (such as tubers)

Sinks include: developing seeds and fruits (which are laying down food stores), and growing roots

40
Q

What are assimilates

A

Products of photosynthesis, such as sucrose

41
Q

What is the definition of translocation

A

The movement of organic solutes through phloem sieve tubes

42
Q

What is passive loading and active loading in the process of translocation

A

Passive: sucrose diffuses through cytoplasm and plasmodesmata (the Symplast route) and enters sieve tubes

Active: sucrose travels through cell walls and intercellular spaces (apoplast route) and eventually reaches companion cells. Sucrose loaded into companion cells through a combination of active transport and facilitated diffusion

43
Q

In both active and passive loading once sucrose is in siege elements what happens

A

Water enters the phloem by osmosis. Turgor (water) pressure causes movement (mass flow) of water and dissolved solutes to regions of lower pressure. Water and solutes are unloaded from sieve tubes at sinks

44
Q

What is evidence for mechanism of translocation includes

A

Observation of proteins require for active transport (advances in microscopy) the lack of translocation if mitochondria in companion cells are poisoned, and analysis of flow rate’s using aphid stylets

45
Q

State 2 examples of translocation source and 2 examples of a sink (4 marks)

A

Sources:
green leaves [1], green stems [1], tubers [1], tap roots [1], food stores in seeds [1]

Sinks:
(Growing) roots [1], meristems [1], developing seeds [1], developing fruits [1], storage organs [1]

46
Q

Explain how sucrose is loaded into phloem cells using a combination of active transport and facilitated diffusion (4 marks)

A

H+ ions moved out of companion cells via active transport [1]
H+ concentration gradient established [1]
Co- transport [1]
Of H+ and sucrose into companion cells [1]

47
Q

What are xerophyte adaptions, what are the benefits

A

Sunken stomata (in pits): traps moist air and reduces transpiration rate

Reduced number of stomata: lowers rate of transpiration

Reduction of leaf area (eg needle-like leaves in conifers): water loss via transpiration is reduced

Thick waxy cuticle: reduces transpiration via the cuticle (which represents approximately 10% of water loss)

Curled leaves (eg in marram grass): provides a long term reserve of water

Leaf loss during dry periods: significantly reduces transpiration when no water is available

Long roots (eg some cactus species): increases the chances of obtaining water from the ground

Biology Year 12 (7 decks)

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