9.1 Xylem Transport

Question 1

How does transpiration work?

Answer 1

Water enters the via the roots, creating a concentration gradient between roots and leaves. Therefore, it travels up to the leaves via the xylem, where it will be converted into vapour by light energy, and it exits via the stomata.

Question 2

Why is transpiration an inevitable consequence of photosynthetic gas exchange?

Answer 2

The gas will travel in and out via the stomata, so they have to be open, so water will naturally go out through them.

Question 3

How is water nicely continuously pulled up to the leaves?

Answer 3

Due to the adhesive and cohesive properties of water, it’s called transpiration stream.

Question 4

How are water losses from the stomata regulated?

Answer 4

Guard cells fill with water when the stomata opens. So when the plant needs to conserve water, it releases abscisic acid, which will makes water leave the guard cells, and thus the stomata close.

Question 5

What do roots do?

Answer 5

They actively pump protons out of the roots, which displace the positive mineral ions from the soil, and then they diffuse into root. Negatively charged minerals might bind to proton and diffuse back in together. Water will follow the mineral ions into the root via osmosis.

Question 6

What are Xerophytes?

Answer 6

-> Tolerate dry conditions
1. Thick cuticle at the top of leaves prevents water from evaporating.
2. They have rolled leaves or reduced/no leaves

Question 7

What are Halophytes?

Answer 7

-> Tolerate salty conditions
All toxic Ions are put into 1 single leaf, which then falls off