Unit 8 : Transport in Plants

Question 1

Function of Xylem

Answer 1

transport water and mineral ions, and support the plant’s overall structure

Question 2

4 Adaptations of Xylem

Answer 2

1. consists of elongated dead cells ( no organelles )
2. arranged end to end to create a hollow tube that reduces resistance and allows a continuous and rapid flow of water
3. thick cell walls that contain lignin for strength to withstand hydrostatic pressure
4. no cytoplasm and nucleus to have less resistance to water flow

Question 3

Function of Phloem

Answer 3

transports sucrose and amino acids from the leaves up and down the stem

Question 4

3 Adaptations of Phloem

Answer 4

1. consists of living cells arranged end to end, contains cytoplasm
2. pores in the end wall so that cell sap can be transported
3. contains companion cells which transports required energy

Question 5

Function of Root Hair Cells

Answer 5

absorb water and minerals from the soil

Question 6

4 Adaptations of Root Hair Cells

Answer 6

1. hair like projection increases surface area to volume ratio
2. thin cell walls to decrease diffusion distance
3. large, permanent vacuole to maintain high concentration of sugar in cell saps.
4. many mitochondria for active transport

Question 7

Explain the Journey of a Water Molecule

Answer 7

water enters the root hair cells form the soil via osmosis. it then enters the root cortex cells, root xylem, and then the leaf mesophyll cells

Question 8

Define Transpiration

Answer 8

loss of water vapour from leaves, which evaporates from the surface of the mesophyll cells into the air spaces and diffuses out of the leaves through the stomata

Question 9

3 Steps of Transpiration

Answer 9

1. water leaves mesophyll cells into air spaces created by an irregular shape of spongy mesophyll cells, then diffuses out of the stomata.
2. water vapour loss is due to the large internal surface area provided by the interconnecting air spaces between mesophyll cells and the size and number of stomata.
3. water moves upwards in the xylem in terms of a transpiration pull that draws up a column of water molecules held together by forces of attraction between water molecules.

Question 10

Define Wilting

Answer 10

occurs if water loss exceeds water uptake – cells become flaccid, and tissues become limp

Question 11

How does Temperature affect the Rate of Transpiration

Answer 11

the kinetic energy of the water molecules increases, so they evaporate and diffuse faster from the mesophyll cells, increasing the transpiration rate

Question 12

How does Humidity affect the Rate of Transpiration

Answer 12

low humidity increases the concentration gradient between the leaf and the atmosphere, hence increasing the transpiration rate

Question 13

How does Wind Speed affect the Rate of Transpiration

Answer 13

removing water molecules to maintain a steep concentration gradient

Question 14

Define Translocation

Answer 14

movement of sucrose and amino acids in the phloem from regions of production (sources) to regions of storage or regions of utilisation in respiration or growth (sinks)

Question 15

Define Sources

Answer 15

parts of plants that release sucrose or amino acids

Question 16

Define Sinks

Answer 16

parts of plants that use or store sucrose or amino acids

Question 17

Explain Translocation in Spring

Answer 17

sucrose transported from stores in roots to leaves

Question 18

Explain Translocation in Summer & Early Autumn

Answer 18

sucrose goes from photosynthesizing leaves to root stores