Exam 4 - Osmoregulation in Plants

Question 1

What is turgor pressure?

Answer 1

pressure exerted by the protoplast against the cell wall

Question 2

How does water cross membranes?

Answer 2

through aquaporins

Question 3

What are the characteristics of aquaporins?

Answer 3

• integral membrane proteins that form water-selective channels across the membrane
• account for observed higher rates of water movement than diffusion alone

Question 4

What are the advantages of aquatic life?

Answer 4

• buoyancy
• abundant water
• moderate temperatures
• filtered light

Question 5

What are the obstacles of living on land?

Answer 5

• no buoyancy
• scarce water
• extreme temperatures
• excess light, including UV

Question 6

What are a plant’s responses to water deficit?

Answer 6

• decreased photosynthesis
• decreased stomatal aperture
• decreased shoot meristem and leaf growth
• decreased water uptake
• increased solute accumulation
• increased root growth

Question 7

What is osmotic adjustment?

Answer 7

-biochemical mechanism that helps plants acclimate to dry or saline/salty soil

Question 8

What is the relationship between solute/osmotic potential and molarity?

Answer 8

directly proportional relationship

Question 9

What does the addition of solute do to solute potential?

Answer 9

decreases solute potential

Question 10

What is pressure potential?

Answer 10

the physical pressure on a solution

Question 11

What does osmotic adjustment result from?

Answer 11

a net increase in the number of solute particles in the plant cell

Question 12

How does osmotic adjustment work?

Answer 12

• solutes are added to the cell, decreasing solute potential
• osmotic adjustment drives water potential in the root lower than in the soil
• water moves down a potential gradient from the soil into the plant

Question 13

What are halophytes?

Answer 13

salt-tolerant plants that are genetically adapted to saline conditions

Question 14

What are glycophytes?

Answer 14

less salt-tolerant plants that are not adapted to saline conditions

Question 15

How do saline environments contribute to cytotoxicity?

Answer 15

cystolic Na+ increases, and the ions can become toxic by denaturing proteins and destabilizing membranes

Question 16

How do halophytes deal with high salinity?

Answer 16

• reduction of Na+ influx
• compartmentalization of Na+ in vacuoles
• excretion of Na+ through salt glands