week 11

Question 1

Where do most plants get their water?

Answer 1

from their roots

Question 2

What are the two methods of xylem sap ascent?

Answer 2

pushing xylem sap
pulling xylem sap

Question 3

How does pushing xylem sap work?

Answer 3

Water flows from root cortex
generates root pressure pushing sap upward
Positive pressure is less common

Question 4

How does pulling xylem sap work?

Answer 4

air outside is drier than inside the leaf
water leaves through stoma
negative water pressure pulls
only works if there is an unbroken chain of water molecules

Question 5

when does guttation?

Answer 5

if more water enters than leaves water droplets can be seen on the tips of the leaves

Question 6

What percentage of atmosphere is made of moisture from transpiration?

Answer 6

10%
some areas >50%

Question 7

Why do do plants need so much water?

Answer 7

95% of water taken up is lost through transpiration
water is a conduit for transport of nutrients
lose water to take up CO2
evaporative cooling

Question 8

What is the driving force of transpiration?

Answer 8

difference in water potential between the soil and the atmosphere surrounding the plant

Question 9

Answer 9

Question 10

What is Evapotranspiration?

Answer 10

Evapotranspiration is the term used to describe the part of the water cycle which removes liquid water from an area with vegetation

Question 11

What is the big leaf approach?

Answer 11

The transpiration of a vegetated surface assumes the canopy vegetation as an ideal big leaf at a virtual hieght