Water and Plant Relations - 2

Question 1

What is the biggest challenge for plants

Answer 1

to balance the uptake, transport, and loss of water when exposed to photosynthesis specifically

Question 2

to prevent desiccation from photosynthesis what must plants do

Answer 2

the must absorb water by the roots and transported throughout the plant body

Question 3

Define turgor pressure

Answer 3

(hydrostatic pressure) - the force within the cell that pushes the plasma membrane against the cell wall.

Question 4

What is the function of turgor pressure

Answer 4

necessary for physiological processes = enlargement, stomal openings, transport processes.
contributes to rigidity and stability of primary cell wall (non-lignified tissue)

Question 5

What is waters high heat capacity important for

Answer 5

controlling and buffering temperature fluctuations in cells

Question 6

What makes water a good solvent and to be readily transported through a plant body

Answer 6

1. hydrogen bonding ability of water
2. polar structure

Question 7

What is waters high latent heat of vaporization important for

Answer 7

is it the amount of energy to convert liquid into vapor (break down H bonds) and is important for moderating temperature of transpiring leaves

Question 8

What are the three “other” important properties of water that result from H-bonds

Answer 8

1. cohesion = mutual attraction between water molecules
2. adhesion = attraction of water to solid surfaces (ex. cell walls)
3. surface tension = develops in water molecules at air and water interface (forming meniscus). water is attracted more to each other and energy is required to overcome this and this input of energy is called surface tension

Question 9

Define diffusion

Answer 9

the random thermal motion of molecules, important over short distances

Question 10

Define osmosis

Answer 10

the net movement of water across a selectively permeable barrier (ex. plant cell membranes)

Question 11

Define water potential

Answer 11

describes the forces acting on water and affecting its movement
related to chemical potential

Question 12

What are the 3 major forces influencing the water potential

Answer 12

concentration, pressure, and gravity

Question 13

Explain concentration potential

Answer 13

solute concentration in cell water, solute dissolved in a solution will decrease the concentration potential

Question 14

explain pressure potential

Answer 14

pressure in cells, positive means in living cells and negative in dead cells

Question 15

water is not pumped through plants but moves due to…

Answer 15

in response to gradients in chemical (water) potential

Question 16

Plants usually have ____ water potential because

Answer 16

negative
because of the high solute content (more solutes than pure water)

Question 17

Water enters or leaves a cell according to the ____

Answer 17

water potential gradient
(seen by flaccid cell in greater potential and water moves in and vise versa)

Question 18

What happens to the water potential if a cell is squeezed

Answer 18

its pressure potential increases and the water potential resulting in water flowing out of the cell

Question 19

cell wall elasticity defines the relation between ___ and ____

Answer 19

turgor pressure and cell volume

Question 20

What determines how fast cells exchange water with their surroundings

Answer 20

the water permeability of the plasma membrane and tonoplast

Question 21

How does turgor pressure change as a result of changes in plant cell volume and why

Answer 21

small changes in plant cell volume, greatly changes the turgor pressure because plant cells are rigid

Question 22

Define aquaporins

Answer 22

integral membrane proteins that form water-selective membrane channels
they alter the rate of water movement, but not the direction or driving force

Question 23

How is the measure of water status of plants often measured

Answer 23

by water potential

Question 24

What is the trade-off of plants in regards to the plants water status

Answer 24

trade-off between benefits of being able to carry out physiological processes over a wider range of environmental conditions AND the costs associated with such capability

Question 25

Stretch activated molecules

Answer 25

located in plasma membrane and may permit cells to change water status by the change in cell volume rather than responding directly to turgor pressure