Transport In Plants

Question 1

Structure and function of Xylem

Answer 1

Hollow dead cells, no end wall, cell wall strengthened with lignin.

Transport for water and dissolved minerals, structural support.

Question 2

Structure and function of Phloem

Answer 2

Sieve plates, companion cells, sieve tube.

Phloem transports food in the form of organic solutes (sap).

Question 3

Structure and function of Root hair cells

Answer 3

Long and thin, large SA:V, thin surface layer

Root hair cell allow substances to enter the root system through the soil, water via diffusion, minerals via active transport

Question 4

Apoplast pathway

Answer 4

The movement of water molecules through the cell walls and intracellular spaces. Water fills the spaces between the loose, open network of fibres in the cell wall. The cohesive forces pull other water molecules along.

Question 5

Symplast pathway

Answer 5

Movement of water molecules through the cytoplasm. Water enters through the plasmodesmata. The further away a cell is from the xylem, the greater the water potential gradient is, meaning water is drawn up.

Question 6

Vacuolar pathway

Answer 6

Movement of water molecules through the vacuoles. Same as symplast pathway.

Question 7

Transpiration

Answer 7

The loss of water vapour from the leaves and stems of a plant. 95% of water absorbed by roots is lost. Water vapour is mainly lost through the stomata, but sometimes from the lenticles in the stem.

Question 8

Transpiration stream

Answer 8

The movement of water (in continuous columns) from the xylem vessels in the roots to the leaves

Question 9

Factors affecting transpiration

Answer 9

Light intensity, relative humidity, temperature, soil-water availability, air movement

Question 10

How to calculate rate of transpiration

Answer 10

Seconds / millimetres travelled by air bubble = rate of transpiration

Question 11

How to set up a potometer correctly

Answer 11

Plant shoot must be cut underwater

Leaves cant have water on them

No air bubbles in apparatus

Question 12

Xerophytes

Answer 12

Plants adapted to living in dry conditions

Question 13

Xerophyte adaptations

Answer 13

Smaller leaves to reduce surface area. Thick waxy cuticles prevent water loss. Close stomata in response to low water availability. Contain hairs and pits which trap moist air. Roll leaves to trap air.

Question 14

Hydrophytes

Answer 14

Plants that actually live in water

Question 15

Hydrophyte adaptations

Answer 15

Have very thin or absent waxy cuticles. Many constantly open stomata to maximise gas exchange. Wide, flat leaves gives a large surface area for light absorption. Some have air sacs to keep them afloat. Many large air spaces to make leaves and stems more buoyant

Question 16

Translocation

Answer 16

Translocation is the transport of assimilates throughout the plant. Translocation occurs in the phloem vessels & requires ATP energy to create a pressure difference.

Question 17

Translocation source

Answer 17

A photosynthesising cell that makes sugars (sucrose) and chemicals that are transported in the phloem vessels

Question 18

Translocation sink

Answer 18

A respiring cell where the sugars and chemicals in the phloem sap are required