Chapter 27.3- water transport

Question 1

What are parenchyma cells and where are they found?

Answer 1

the layer of thin walled epidermal cells
they form a network of veins

Question 2

What are phloem cells?

Answer 2

the outer tissue of cells that is responsible for transporting carbonhydrates

signaling molecules

Question 3

What are xylem?

Answer 3

They are inner tissues that transport water from root to leaves

signaling molecules

Question 4

Why does xylem tissues transport water and how does its cell structure aid this?

Answer 4

• water can easily flow through it
• ## they lack any cytoplasm or membranes that require diffusion

Question 5

How does water flow through xylem cells?

Answer 5

1. water flows through the opened tubes water conduits
2. travels the entire length of vessel
3. water leaves by traveling out of the pit an exiting

Question 6

What factors affect the rate in which water flows through conduits?

Answer 6

Conduit length: The longer the conduit the less water has to travel from one pit to another pit which is helpful

Conduit width: The bigger the radius the easier water can flow without pressure

Question 7

How does pressure/evaporation pumps help the transport of water in photosynthesis?

Answer 7

transpiration lowers the pressure of water in the xylem near the site of evaporation for leaves so that water can travel up from soil

Question 8

Why is the ideal water pressure for xylem leaves zero? or even less than zero

Answer 8

because with the water pressure being zero water can be transpired quicker and more efficiently.

Question 9

How does water move through xylem?

Answer 9

1. the evaporation of water in the leaves causes the pressure in the xylem to decrease
2. Hydrogen bond form between water molecules to be pulled by the xylem
3. The negative pressure in the xylem must overcome the surface tension of air-water interfaces in the soil

Question 10

What is water potential?

Answer 10

• water potential is the free energy of water and, therefore, its capacity to do work. Water moves from high potential areas to low potential areas

Question 11

What are the risks of water transport?

Answer 11

1. collapse: When tension in the xylem is too large it can cause the xylem to collapse but lignin lowers the risk of that by providing more structural support.
2. Cavitation: is when liquid water under tension is replaced by liquid vapor. It blocks water flow. by creating gas bubbles

Question 12

What are the ways to prevent cavitation? and how are they are introduced

Answer 12

1. root tissues inhibits the formation
2. tiny bubbles are pulled through the pit during periods of drought
3. when gas comes out of a solution during freezing