Xylem

Question 1

mass transport system

Answer 1

• transports water an mineral ions in solution

- move up the plant from roots to the leaves

Question 2

structure

Answer 2

• xylem vessels part of xylem tissue that transports water and ions
• vessels very long tube-like structures from dead cells joined end to end
• no end walls on these cells making an uninterrupted tube that allows water to pass up through the middle easily

Question 3

cohesion + tension

Answer 3

• water evaporates from leaves at the top of xylem = transpiration
• creates tension which pulls more water into the leaf
• water molecules are cohesive so when some pulled into leaf the others follow
• whole column of water in the xylem from the leaves down to the roots move upwards
• water then enters the stem through the roots

Question 4

Transpiration

Answer 4

• evaporation of water from a plants surface
• water evaporates from the moist cells wall and accumulates in the spaces between cells in the leaf
• when stomata open it moves out of the leaf down the water potential gradient
• more water inside leaf then air outside

Question 5

factors affecting transpiration rate

Answer 5

• light intensity
• temperature
• humidity
• wind

Question 6

light intensity

Answer 6

• lighter = faster
• stomata open when it gets light to let in carbon dioxide for photosynthesis
• dark stomata closed so there’s little transpiration

Question 7

temperature

Answer 7

• higher = faster
• warmer water molecules have more energy so evaporate from cells inside the leaf faster
• increase water potential gradient between the inside and outside of the leaf
• water diffuse out of leaf faster

Question 8

humidity

Answer 8

• lower = faster
• air around plants dry
• the water potential gradient between the leaf and air is increased
• increasing rate

Question 9

wind

Answer 9

• windier = faster
• lots of air movement blows away water molecules from around the stomata
• increasing water potential

Question 10

potometer

Answer 10

measures water uptake

• cut shoot underwater to prevent air from entering xylem so cut it at a slant to increase surface area available for water uptake
• assemble potometer under water and insert the shoot with apparatus still under water so no wai comes in
• remove apparatus from water but keep end of capillary tube submerged in a beaker of water
• check apparatus is water tight and air tight
• dry the leaves so it allows time for shoot to acclimatise and then shut the tap
• remove end of capillary tube from beaker of water until one air bubble has formed then put the end of tube back into water
• record starting position of air bubble
• start stop watch and record distance moved by bubble per unit time
• rate of air bubble movement is an estimate of transpiration rate