7.8 - Water Transport in Plants Flashcards
How water moves through a plant The cohesion-tension theory How transpiration relates to gas exchange How to use a potometer to estimate transpiration rate
How does water enter a plant?
Through root hair cells via osmosis
How does water move through a plant?
Root hair cells to xylem xylem to leaves evaporation from leaves
What theory explains how water moves up the xylem?
Cohesion-tension theory
What is cohesion?
Hydrogen bonding causes water molecules to stick together
What is adhesion?
Hydrogen bonding between water and xylem walls pulls water upwards
What is transpiration pull?
Evaporation creates tension transmitted down water column
What is transpiration?
Evaporation of water from aerial plant parts
Why does transpiration occur?
Water evaporates stomata open water vapour moves down gradient
What factors affect transpiration rate?
Light intensity temperature humidity wind speed
How does light intensity affect transpiration?
High intensity opens stomata increasing rate
How does temperature affect transpiration?
High temperature increases evaporation increasing rate.
How does humidity affect transpiration?
Low humidity increases water vapour gradient increasing rate.
How does wind speed affect transpiration?
High wind speed increases water vapour gradient increasing rate.
What is a potometer used for?
Measure rate of transpiration
What are the steps in using a potometer?
Cut shoot assemble potometer keep tube submerged check airtight dry leaves acclimatise form air bubble measure distance time change one variable
How do you calculate the cross-sectional area of the capillary tube?
πr2
How do you calculate the volume of water uptake?
πr2 x d
How do you calculate the rate of transpiration?
Volume of water uptake / time taken
