Plant Transport

Question 1

Vascular plants

Answer 1

Plants that required a specialized transport system.

Question 2

Substances plants transport

Answer 2

-CO2
-O2
-Water
-Organic nutrients
-Inorganic ions
-Hormones

Question 3

Transpiration system

Answer 3

Passive system that moves water molecules and dissolved mineral ions upwards through the xylem.

Question 4

Translocation

Answer 4

The active movement of assimilates (sugars and amino acids) bidirectionally through the phloem cells from sources to sinks.

Question 5

Vascular bundle (roots)

Answer 5

Xylem in ‘x’ shape in centre.
Phloem in four sections around the middle.

Question 6

Vascular bundle (stem)

Answer 6

Xylem located inside for support.
Phloem located outside.
Separated by layer of cambium tissue, containing meristem cells.

Question 7

Vascular bundle (leaves)

Answer 7

Xylem on top.
Phloem on bottom.

Question 8

Adaptations of xylem

Answer 8

-No nucleus or cytoplasm
-Thin lumen for easy water cohesion
-Continuous columns do not impede movement.

Question 9

Lignin

Answer 9

-Impregnates xylem walls, strengthening them, preventing collapse and making them waterproof.

Question 10

Ring like patterns in the lignin

Answer 10

Allow the stem to grow and bend.
Can be straight, spiral or reticulate.

Question 11

Bordered pits

Answer 11

Areas of incomplete lignification which allows water to move sideways between vessels.

Question 12

Parenchyma cells

Answer 12

Surround xylem
Store food
Contain tannin deposits, which protects against herbivores.

Question 13

Sieve tube elements

Answer 13

Elongated cells lined end to end.
Lumen is where material is transported in the phloem.

Question 14

Sieve plates

Answer 14

Perforations between sieve tube elements that allows sap to move between elements and support the lumen.
Can close in the event of injury to prevent sap from escaping.

Question 15

Companion cells

Answer 15

Runs alongside STE’s, linked by gaps in the cell wall.
Large nucleus and many mitochondria to produce the energy needed.

Question 16

Osmosis

Answer 16

Movement of water from a high ψ to an area of low ψ through a semi-permeable membrane.

Question 17

Plasmolysis

Answer 17

External ψ means water moves out of the cell and cell membrane moves away from the cell wall.

Question 18

Root hair cells

Answer 18

200-250um
Thousands on each root, elongated with hairs to maximise diffusion.

Question 19

Symplast pathway

Answer 19

Water moves through the cytoplasm of the cells.
Changes cells through the plasmodesmata.
Each cell away from the root has a lower water potential so water is drawn up the plant.

Question 20

Vacuolar pathway

Answer 20

Water moves through the cytoplasm but also the vacuoles.
This is the slowest route.

Question 21

Apoplast pathway

Answer 21

Water moves through the cell wall and intracellular spaces.
It is pulled up by cohesion.

Question 22

Casperian strip

Answer 22

Impermeable band of subarin in the endodermis, that forces water from the apoplast pathway to the symplast.

Question 23

Evidence for root pressure (temperature)

Answer 23

Higher temp increases the pressure.
This suggests an enzyme controlled reaction as they are reaching closer to their optimum temperature.

Question 24

Evidence for root pressure (reactant levels)

Answer 24

If oxygen or substrate levels drop the root pressure decreases.
Suggesting catalysed reactions.

Question 25

Evidence for root pressure (cut stems)

Answer 25

During guttation, sap and water will be forced out. This would only happen during active transport, not transpiration.

Question 26

Evidence for root pressure (cyanide)

Answer 26

Cyanide applied to the root stops mitochondria from producing energy. Suggests active pumping as energy is being required.

Question 27

Transpiration (mesophyll)

Answer 27

Once water enters the leaves in passes into the mesophyll cells and evaporates into large air spaces between the cells. This means the water potential is higher inside the plant than outside, and water will exit via diffusion.

Question 28

Stomata

Answer 28

Where most water is lost via transpiration. Found on the underside of leaves. Opened and closed by guard cells.

Question 29

Cohesion-tension theory

Answer 29

Water is a polar molecule. In xylem, water molecules arrange so positive and negative poles stick to each other. When some leave the plant by transpiration others are pulled up behind them.

Question 30

Evidence for cohesion tension

Answer 30

High transpiration rates cause tree diameter to decrease due to tension. Broken xylems stop drawing up water as the air breaks the transpiration system.

Question 31

Effect of humidity on transpiration

Answer 31

More humidity leads to less transpiration, until the water conc is greater outside the leaf and it levels out.

Question 32

Effect of wind velocity on transpiration

Answer 32

Greater velocity leads to greater transpiration rate.

Question 33

Effect of temperature on transpiration

Answer 33

Higher temperature causes transpiration to rapidly increase, before levelling out completely.

Question 34

Effect of light intensity on transpiration

Answer 34

Greater light intensity increases transpiration before levelling out.

Question 35

Precautions to increase validity of potometer

Answer 35

Set up and cut stem underwater Cut stem at an angle Seal up any potential gaps Allow time for the plant to adapt

Question 36

Sources (translocation)

Answer 36

Provide assimilates to the plant from reactions or storage

Question 37

Examples of sources

Answer 37

Green leaves, tubers, root taps, food stores in seeds

Question 38

Sinks (translocation)

Answer 38

Use assimilates in various processes

Question 39

Examples of sinks

Answer 39

Growing roots, meristem cells, seeds, fruits, storage organs

Question 40

Phloem loading

Answer 40

Hydrogen ions are pumped out of companion cells actively. Provides an electrochemical gradient for sucrose to move into a cell via a co-transporter. H+ ions return Sucrose diffuses into sieve tube element.

Question 41

Mass flow at the source

Answer 41

Sugar now in sieve tube decreases the water potential. This means water moves from companion cells into sieve cells via osmosis.

Question 42

Mass flow at the sink

Answer 42

-Assimilates move actively or passively out of sieve cells. -This increases their water potential and means water moves out.

Question 43

Evidence for mass flow

Answer 43

Inhibiting aerobic respiration in companion cells stops translocation (energy is not produced) Flow of sugars 10000x faster than by diffusion Ringing a tree causes sugars to collect above the ring