plant transport

Question 1

xylem function

Answer 1

transport water + mineral ions

Question 2

phloem function

Answer 2

transport sucrose + amino acids

Question 3

xylem structure

Answer 3

• long, narrow tubes
• hollow, dead cells
• joined end-to-end without cross wall + extend as continuous tubes from roots to stems to leaves
• walls strengthened with lignin
• lignin + cellulose strengthen and keep plant upright

Question 4

pathway of water uptake

Answer 4

• water enters RHC by osmosis
• water enters RCC by osmosis
• water enters root xylem at high pressure (root pressure) by osmosis
• water travels in xylem in continuous stream (transpiration stream) due to cohesion + adhesion
• as water evaporates from mesophyll cells so water enters the leaf from xylem due to transpiration pull

Question 5

transpiration

Answer 5

evaporation of water from the surfaces of mesophyll cells into air spaces + loss of that water vapour through the stomata

Question 6

effect of temperature on transpiration

Answer 6

as temperature increases kinetic energy of water and rate of evaporation increases so transpiration rate increases

Question 7

effect of humidity on tranpiration

Answer 7

in low humidity theres a greater concentration gradient between atmosphere and inside of leaf so diffusion rate increases so transpiration rate increases

Question 8

effect of wind velocity

Answer 8

with high wind velocity wind sweeps away water as soon as it leaves stomata so it maintains a high concentration gradient so transpiration rate increases

Question 9

water loss is related to

Answer 9

large internal surface area between air spaces + no. of stoma

Question 10

transpiration pull

Answer 10

results from evaporation of water creating a gradient that draws up water to replace the lost amount + cohesion

Question 11

how and why wilting occurs

Answer 11

when transpiration is higher than water uptake water starts to be lost so cells lose turgidity and stems droop

Question 12

translocation

Answer 12

movement of sucrose + amino acids in the phloem

Question 13

sources of plant

Answer 13

parts of plant that release sucrose + amino acids

Question 14

sinks of plant

Answer 14

parts of plant that store sucrose + amino acids

Question 15

why sources and sinks differ at times

Answer 15

• during daylight, source would be leaves and sinks would be roots (non-photosynthesising parts)
• during darkness or cold sources would be roots and other parts will be sinks