Transport In Plants

Question 1

Why do plants need transport systems

Answer 1

Metabolic demands
Size and small surface area to volume ratio

Question 2

Xylem structure and functions

Answer 2

Non living tissue that transports water and ions and supports
Long hollow structure made by columns of cells end to end
Lignified walls for strength - water proof

Question 3

Phloem structure and function

Answer 3

Living tissue that transports dissolved sugars eg sucrose
Sieve tubes elements to form a long hollow structure and not lignified
Perforated with sieve tube to flow sugars through
Companion cells have mitochondria to produce ATP

Question 4

Symplast movement

Answer 4

Cytoplasm connected by the plasmodesmata. Root hair cell has a higher water potential than the next cell and moves by osmosis and maintains a steep water potential gradient

Question 5

Apoplast movement

Answer 5

Movement by cell walls. Water fills spaces in the cell walls. More water molecules are pulled through apoplast due to cohesive forces. Pull from water creates a tension causing a continuous flow of water

Question 6

Transpiration

Answer 6

CO2 moves into leaf and O2 moves out by diffusion down a concentration gradient through the stomata. Can be opened by guard cells. Stomata open and water vapour moves out causing transpiration

Question 7

Transpiration stream

Answer 7

Water moves in by osmosis and across membranes and by diffusion in the apoplast pathway. Moves water from roots to highest leaves and water evaporates from mesophyll surface into air spaces in leaf down a conc gradient.
Loss of water lowers water potential in cells so water moves into cell from another cell and repeated until reaches xylem; water molecules from h bonds of xylem and sticks to each other ( cohesion and adhesion)
Water drawn up xylem in a continuous stream to replace water and results in cohesion tensions

Question 8

Factors affecting transpiration

Answer 8

1. Light intensity
2. Temperature
3. Humidity
4. Wind

Question 9

Translocation - loading

Answer 9

Loading:
- active process by the apoplast route. Sucrose travels from source to companion cells by diffusion down a conc gradient. Sucrose moved into cytoplasm across membranes. Hydrogen pump actively out companion cells into surroundings tissue (ATP) and ions return to companion cell down a conc gradient via protein. Sucrose conc in companion cells increases
Water moves in by osmosis and leads to build in turgor pressure and moves by mass flow

Question 10

Translocation - unloading

Answer 10

Unloads by diffusion of the sucrose from phloem into surroundings cells. Rapidly moves into cells by diffusion or converted into substances so concentration gradient is maintained. Loss of solutes leads to increase of water potential by osmosis. Some water is drawn into transpiration stream in xylem

Question 11

Xerophytes adaptions

Answer 11

1. Waxy thick cuticle
2. Hairy leaves
3. Sunken and reduced stomata
4. Curled leaves
5. Leaf loss - transpiration in stem
6. Root adaptations

Question 12

Hydrophytes adaptions

Answer 12

1. Thin or no waxy cuticle
2. Many stomata, always open
3. Reduced structure
4. Wide flat leaves
5. Small roots
6. large SA Vol area
   Air sacs