Plant Transport ✅

Question 1

What are the key functions of water

Answer 1

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

Question 2

Definition of xerophytes

Answer 2

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

Question 3

What is definition of hydrophytes

Answer 3

A plant which grows only in or on water

Question 4

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

Answer 4

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

Question 5

What is the Need for Transport Systems in Plants

Answer 5

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

Question 6

What is an exchange site

Answer 6

The location within an organism where exchange occurs

Question 7

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

Answer 7

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

Question 8

Why do larger organisms require specialised mass transport systems

Answer 8

Increasing transport distances

Surface area: volume ratio

Increasing levels of activity

Question 9

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

Answer 9

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

Question 10

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

Answer 10

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

Question 11

What is mass flow

Answer 11

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

Question 12

Mass transport systems help to…

Answer 12

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

Question 13

What does xylem transport and is it alive or dead

Answer 13

Water and mineral ions, dead

Question 14

What does phloem transport and is it alive or dead

Answer 14

Sucrose and other nutrients, alive

Question 15

Why do plants not have a specialized transport system

Answer 15

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

Question 16

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

Answer 16

Know it

Question 17

How do xylem cells key features work

Answer 17

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

Question 18

What is the function of xylem cells

Answer 18

Transport of water and minerals up a plant

Tissue also provides structural support for plant

Question 19

How do phloem key features work

Answer 19

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)

Question 20

What is the function of phloem cells

Answer 20

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

Question 21

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

Answer 21

Central in roots;
Towards the outside of stems

Question 22

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

Answer 22

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

Question 23

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

Answer 23

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

Communication between the 2 types of cell occurs through plasmodesmata

Question 24

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

Answer 24

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)

Question 25

How does water move into root hair cells

Answer 25

Osmosis

Question 26

how does water enter the xylem

Answer 26

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

Question 27

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

Answer 27

Apoplast pathway= through cell walls Symplast= through the cytoplasm

Question 28

State 2 uses of water in plants (2 Marks)

Answer 28

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

Question 29

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

Answer 29

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

Question 30

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

Answer 30

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]

Question 31

What is transpiration

Answer 31

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

Question 32

Explain transpiration and water movement through xylem

Answer 32

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)

Question 33

What is the evidence for cohesion-tension theory

Answer 33

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

Question 34

List environmental factors that effect transpiration rate

Answer 34

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

Question 35

List factors within a plant that affects transpiration rate

Answer 35

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

Question 36

Describe how to do measuring transpiration practical

Answer 36

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

Question 37

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

Answer 37

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]

Question 38

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)

Answer 38

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

Question 39

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

Answer 39

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

Question 40

What are assimilates

Answer 40

Products of photosynthesis, such as sucrose

Question 41

What is the definition of translocation

Answer 41

The movement of organic solutes through phloem sieve tubes

Question 42

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

Answer 42

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

Question 43

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

Answer 43

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

Question 44

What is evidence for mechanism of translocation includes

Answer 44

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

Question 45

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

Answer 45

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]

Question 46

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

Answer 46

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]

Question 47

What are xerophyte adaptions, what are the benefits

Answer 47

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