Water Acquisition

Question 1

What are some examples of exception to uptake of water by roots?

Answer 1

Epiphytes, aquatic plants, parasites

Question 2

Where does water in the soil come from?

Answer 2

Precipitation, irrigation

Question 3

What are the two types of root systems?

Answer 3

Taproot and fibrous

Question 4

What plants have taproots?

Answer 4

Gymnosperms, eudicots

Question 5

What plants have fibrous systems?

Answer 5

Monocots

Question 6

What is the uptake of water and nutrients determined by?

Answer 6

Surface area, particularly of new roots, and fungal associations

Question 7

Identify the root systems

Answer 7

A: fibrous
B: taproot

Question 8

Which root system is better equipped for drought? Why?

Answer 8

Taproot systems reaches deeper into soil for water.

Question 9

What is leftover after gravitational water is drained?

Answer 9

Capillary water

Question 10

What is the field capacity?

Answer 10

Maximum capillary water

Question 11

What are some problems with gravitational wateR?

Answer 11

Flooding
Low O2, which diffuses faster in air than water
Poor root growth
Wilting

Question 12

How are mangroves adapted to water?

Answer 12

Aerial roots above water to take in air

Question 13

How is rice adapted to wateR?

Answer 13

Rice takes in air through stem and leaves, roots go through programmed cell death, providing passageways for air

Question 14

Which holds the most capillary water and why: sand and clay

Answer 14

Sand is reltively large with small SA:V ratio, clay is the opposite. Clay thus has more capillary water, sand is more free draining

Question 15

How does water move through soil?

Answer 15

Bulk flow

Question 16

What is bulk flow of water through soil affected by?

Answer 16

Gaps between soil particles

Question 17

What are the three factors of soil water potential? Which is more important?

Answer 17

Solute potential, pressure potential, matrix portential, solut potential

Question 18

What increases the SA for water uptake?

Answer 18

Root hairs

Question 19

Which parts of the root take up water? Which aids in stabilization?

Answer 19

Younger (that have root hairs) take up water, older aid in stability as they have lost their root hairs.

Question 20

What produces root hairs

Answer 20

Trichoblast

Question 21

What is the symplastic route of water movement?

Answer 21

Movement through living pars of the root

Question 22

What is the apoplastic route of water movement?

Answer 22

Through non-living parts (cell walls, intercellular spaces)

Question 23

When does water enter the root?

Answer 23

When the water potential of root cell is more negative than the water potential of the soil

Question 24

Why does removing water from the soil reduce the water potential gradient?

Answer 24

• As water is drawn out, soil particles dry, matrix potential decreases
• Solutes in soil become more concentrated and osmotic potential becomes more negative
• Eventually potential of soil and root become equal, water uptake ceases (permanent wilting point of the soil)

Question 25

What is the visible sign of root pressure?

Answer 25

Dew

Question 26

What causes dew?

Answer 26

High soil water content and cool, damp atmosphere

Question 27

What is the cause of root pressure?

Answer 27

- Shoot needs ions to support growth - Ions transported from soil into root, then stele - Exported to shoot, but accumulate in root when transpiration is low - Water potential gradient forms, water moves into stele, creating pressure

Question 28

What is the adequate zone?

Answer 28

Concentration of particular ion where the plant's growth is 90% normal or above

Question 29

What is the deficiency zone?

Answer 29

Not enough of ion, growth limited below 90%

Question 30

What is the toxic zone?

Answer 30

Concentration of ions that becomes toxic, growth drops below 90%

Question 31

What is meant by some halophytes being osmatic adjusters?

Answer 31

Osmotic adjusters: exclude salt, cells produce osmotically active compounds to prevent net flow of water potential out by reducing water potential

Question 32

What is a cost of tolerating salt?

Answer 32

Slower growth

Question 33

What is meant by some halophytes being salt accumulators?

Answer 33

Sequester salt in vacuole. Accumulate organic osmolytes in cytoplasm Ionic balance achieved

Question 34

How do some halophytes use salt glands?

Answer 34

Salts exported to external glands or bladders on leaves, leaves are shed, lowering local salt concentrations

Question 35

What do high salt environments do to proteins?

Answer 35

Salts disrupt hydration shells around proteins, leading to denaturation

Question 36

How are proteins protected from salts?

Answer 36

Surrounded by compatible solutes that act as hydration cells.

Question 37

What are costs to tolerating salt and drought?

Answer 37

- Moving ions requires energy - Root systems already require energy without drought or salt stress - Can reduce fitness if stress is not imposed

Question 38

How can tolerance costs be reduced?

Answer 38

Make responses inducible as opposed to constituted.

Question 39

How do plants respond to stress?

Answer 39

Change in gene expression

Question 40

What must plants be able to do to respond to stress?

Answer 40

1. Detect stress 2. Activate appropriate genes to produce appropriate proteins