Transport in Vascular Plants

Question 1

Xylem

Answer 1

Transports water and nutrients from soil (travels up from roots to leaves)

Question 2

Phloem

Answer 2

Transports sugars (travels up and down)

Question 3

Osmosis

Answer 3

The diffusion of water across a selectively permeable membrane from an area of high concentration to an area of low concentration

Question 4

Transport in the Root - Water

Answer 4

Cytoplasm of plant cells have lower concentration of water molecules than the soil water, so water enters passively via osmosis

Question 5

Transport in the Root - Nutrients

Answer 5

Concentration of nutrients in plants is higher than in soil, so nutrients will not enter through diffusion but by active transport (requires energy)

Question 6

Casparian Strip

Answer 6

Prevents nutrients & water from leaking back out of root –> once liquid passes casparian strip, liquid is called xylem sap and moves up stem

Question 7

Transport in the Stem - Root Pressure

Answer 7

As nutrient concentration increases in xylem, more water pulled into xylem (concentration gradient), creating root pressure and pushing xylem sap upwards

Question 8

Transport in the Stem - Capillary Action

Answer 8

Tendency of liquid in a narrow tube to rise or fall due to attractive forces of water –> molecules stick to each other and move up

Question 9

Capillary Action - Cohesion

Answer 9

When particles of the same substance stick together

Question 10

Capillary Action - Adhesion

Answer 10

When a substance sticks to an unlike substance

Question 11

Transport in Leaves

Answer 11

Plants release water vapour through their stomata during transpiration (the evaporation of water from plant leaves - main driving force of transport) –> water vapour is attracted to stomata when they open, because water molecules have attractive forces, one molecule will pull a neighbouring molecule with it creating a train

Question 12

Transpiration

Question 13

Turgor Pressure

Answer 13

When there is excess water, central vacuole is full and it causes a pressure on the cell called turgor –> when plant does not have enough water, it wilts

Question 14

Sugar Sources and Sinks

Answer 14

A cell with high concentration of sugars = source (ex. mesophyll cells)
A cell with low concentration of sugars = sink –> may convert sugars to starch or store them for later use (ex. fruits)

Question 15

Direction of Sugar Transport

Answer 15

Source to sink –> meaning sugar can move up or down
In angiosperms:
- Summer: source is leaves, sink is roots
- Spring: source is roots, sink is leaves

Question 16

Sugar Transport in Phloem

Answer 16

1. Source to phloem: energy used to move sugar into phloem, water follows from xylem cells by osmosis, increasing turgor pressure
2. Translocation: sugars moving quickly between phloem cells, pushing sugar to sink cells
3. Phloem to sink: sink cells have lower concentration of sugars so diffusion is used, water then moves back to xylem