3.1.3

Question 1

Why is transport needed in plants?

Answer 1

*Water, organic substances, mineral ions needs to get around.

Question 2

What does the vascular bundle look like in roots?

Answer 2

*Xylem start shaped centre, phloem in between star points

Question 3

What does the vascular bundle look like in stems?

Answer 3

*Several vascular bundles (around 6)
*upside-down droplet
*Xylem inner edge, Phloem outer, cambium in-between

Question 4

What does the vascular bundle look like in a leaf?

Answer 4

*Xylem towards top
*Phloem bottom

Question 5

What is the structure and function of sieve tubes in phloem?

Answer 5

*S- ↓organelles
F↓ obstruction for cell sap mass flow
*S perforated cross walls(sieve plates)
F sap can move cell to cell

Question 6

What is the structure and function of companion cells in phloem?

Answer 6

S- All organelles
F Provide sieve tubes with E.G ATP through plasmodesmata

Question 7

What are plasmodesmata?

Answer 7

*Channels connecting adjacent plant cells
-e.g. connecting sieve tubes and companion cells

Question 8

What are sieve plates?

Answer 8

perforated end walls connecting sieve tube elements in the phloem

Question 9

What is lignification?

Answer 9

Deposition of lignin in cell walls

Question 10

Why are xylems cells dead

Answer 10

*Lignification waterproofs xylem, killing cells

Question 11

What is capillary action ?

Answer 11

*Mass flow of liquid up tube from adhesion and cohesion

Question 12

What is the structure and function of the xylem?

Answer 12

*S- long continuous dead cells
F- no obstruction organelles
*S lignin walls, spiral, angular, reticulate
F- prevents collapses, keeps tubes open when H2O low- stretch and bend
S- Lignification not complete= bordered pits
F- Allows H2O to other parts of plant
*S- Narrow vessels
F- H bonds can form for capillary action

Question 13

How does water enter the plant?

Answer 13

*From soil to root hair cells by osmosis
*as root hair cells have lower Ψ from mineral ions

Question 14

How does water enter the xylem

Answer 14

*After in root, symplast or apoplast pathway

Question 15

How does water reach the xylem via the symplast pathway?

Answer 15

*H2O passes cell membrane, travels through cytoplasm
cell to cell by osmosis through plasmodesmata
*Each successive cell = lower Ψ

Question 16

How does water reach the xylem via the apoplast pathway?

Answer 16

*Water travels through cell walls
*Wall permeable, fillable spaces between cellulose molecules
*Moves between these spaces not passing membrane
*Mass flow( Cohesive forces H2O) allows mineral ions to be moved
*Stops at casparian strip where it jumps into cytoplasm and travels rest like symplast

Question 17

What is the casparian strip?

Answer 17

*Waterpoof strip outside xylem
*To stop H2O leaking

Question 18

Why is apoplast pathway faster than symplast?

Answer 18

*No resistance from cell membrane

Question 19

What theory describes how water moves up the xylem?

Answer 19

Cohesion-tension theory

Question 20

State the elements of the how water moves up xylem

Answer 20

Cohesion tension theory
Capillary action
Root pressure

Question 21

Describe transpiration tension.(Cohesion tension theory)

Answer 21

*H2O vapour lost. Evaporation mesophyll cells to airspaces/ stomata holes to atmosphere.
*Water drawn in down conc grad to replace - negative pressure
*Continuous stream from cohension = mass flow.

Question 22

Describe Capillary action

Answer 22

*Adhesion to lignin walls pulls up xylem. Cohesion= continuous column
*Narrow diameter reduces air bubbles.

Question 23

Describe root presuure

Answer 23

*Mineral ions low, lowers Ψ H2O enters xylem by osmosis down Ψ grad.
*Hydrostatic pressure increases, flows up plant towards pressure grad

Question 24

What are limitations of potometry to measure transpiration rate ?

Answer 24

• Not all water uptake is transpired.
  *Plant is dead, and so may uptake less water.

Question 25

How do you set up a potometer to improve accuracy.

Answer 25

*Cut shoot underwater- reduce air bubbles *Cut slanted to increase SA for uptake *Grease joints/ add petroleum jelly- ensures airtight -As air disrupts continuous stream.

Question 26

How do you start measuring transpiration in a potometer?

Answer 26

Remove end of capillary tube to get air bubble, start.

Question 27

What factors effect rate of transpiration and why?

Answer 27

* ↑Light intensity- ↑ stomata opening for photosynthesis ↑ SA for evaporation H2O vapour. * ↑Temperature- ↑ KE of H2O molecules ↑ evaporation * ↑Humidity- ↓. - ↑ vapour outside ↓ Ψ grad *↑ Wind- ↑. Removes H2O vapour outside. Steeper Ψ conc grad * ↑ Water availability ↑. As if ↓ stomata close.

Question 28

What is an xerophyte?

Answer 28

A plant adapted to hot conditions

Question 29

How is marram grass adapt to heat?

Answer 29

*Curled leaves = traps air *Hairs on lower surface *Sunken stomata- Traps moist air close t stomata - ↑ humidity, H2O vapour trapped lowers Ψ grad, reduced evap *Long vertical roots- Reach lots of water *Thicker cuticle to ↓ transpiration by ↑ diffusion distance

Question 30

How is a cactus adapted to the heat?

Answer 30

*Spines instead of leaves- ↓ SA of stomata ↓ evap H2O vapour, -traps moist air ↑ humidity, H2O vapour trapped lowers Ψ grad, reduced evap *Open stomata at night, colder and more humid air *Extensive shallow roots- absorbs H2O before evaporates *Succulents store H2O in stem *In dry periods stem tightens to ↓ SA for H2O loss *Thick waxy cuticle to reduce H20 loss

Question 31

What is a hydrophyte?

Answer 31

* Plants adapted to wet conditions

Question 32

How are water lilies adapted to there enviroment?

Answer 32

* Very thin waxy cuticle- don't need to conserve H2O & nutrients dissolve in easier *Stomata on upper surface, with waxy cuticle-Gas exchange faster in air, stomata kept open *Wide flat leaves- ↑ SA for gas exchange, water loss * Aerenchyma present- buoyant. ↑Light, diffusion of O2 on surface *Small roots- less H2O needed *Divided leaf shape- ↑ SA & ↓ damage to left from H2O resistance

Question 33

What are bordered pits?

Answer 33

Areas of the xylem wall where lignification isn’t complete, allows water transfer.

Question 34

What are assimates?

Answer 34

Products of photosynthesis e.g sucrose, animo acids

Question 35

What is translocation?

Answer 35

Movement of assimilates across plant. source to sink.

Question 36

What is the source and sink in plants?

Answer 36

Source- where assimilates made, and photosynthesis occurs -e.g. mesophyll Sink- Where used/stored

Question 37

Describe the process of translocation.

Answer 37

*Active uploading -H+ from companion cells move into source cells via active transport -H+ and sucrose move down conc grad via facilitated diffusion from source to companion cell. -using co-transport molecules * ↑ sucrose conc in companion. Moves via diffusion into sieve tubes through plasmodesmata. *so sieve tube Ψ ↓ *Water in by osmosis, in bordered pits, ↑ hydrostatic press *↓er hydrostat press near sink cells, assimilates move along hydrostatic pressure grad *Diffuse in sink cells *sucrose used/converted, ↑Ψ, water moves out & hydrostatic press kept low

Question 38

Why is Hydrostatic pressure always kept low at sink cells

Answer 38

*When arrive at sink: -Sucrose converted to glucose for respiration -or to insoluble starch for storage *Water Ψ↑, moves out (osmosis), hydrostatic pressure decreases.