Xylem

Question 1

What is lignin?

Answer 1

a complex polymer that binds with cellulose to provide great strength and rigidity to the cell walls of the xylem vessels

Question 2

What is capillary action?

Answer 2

To flow in opposition of gravitational forces (like a straw)

Question 3

What is the adhesive property of water?

Answer 3

Attraction to charged or polar surfaces to stick together, allows for capillary action

Question 4

What is the cohesive property of water?

Answer 4

Attraction of like molecules to stick together

water can create surface tension

Question 5

What is a hydrogen bond?

Answer 5

a intermolecular bond where the partial negative charge on the O of one molecule can form a hydrogen bond with the partial positive charge on the hydrogens of other molecules.

Question 6

What is transpiration?

Answer 6

the loss of water vapor from the stems and leaves of plants, aka a consequence of gas exchange in the leaf

Question 7

Does what flow through the xylem along or against the pressure gradient?

Answer 7

Along the pressure gradient

Question 8

What is the pressure gradient of water via the xylem?

Answer 8

Low pressure in leaf
High pressure in roots

Question 9

What is transpiration pull?

Answer 9

The tension force in a leaf cell wall caused by a negative pressure gradient within the leaf.

Question 10

What is abscisic acid (ABA)?

Answer 10

Plant hormone that can induce stress defense genes, closing of stomata, and to inhibit germination and early seedling growth.

Question 11

What secretes abscisic acid?

Answer 11

Dehydrated mesophyll cells

Question 12

What does abscisic acid trigger?

Answer 12

triggers the efflux of potassium from guard cells, decreasing water pressure within the cells (lose turgor)

Question 13

What are tracheids?

Answer 13

tapered cells that exchange water solely via pits, leading to a slower rate of water transfer

Question 14

What are the two types of xylem vessels?

Answer 14

Annual vessels and spiral vessels

Question 15

How does lignin deposit in annular vessels?

Answer 15

the lignin forms a pattern of circular rings at equal distances from each other

Question 16

How does lignin deposit in spiral vessels?

Answer 16

The lignin is present in the form of a helix or coil

Question 17

What increases thee surface area available for absorption in some root cells?

Answer 17

Root hairs

Question 18

What are the minerals that need to be taken up from the soil?

Answer 18

Mg, nitrates, Na, K, PO

Question 19

For what do the roots take up magnesium?

Answer 19

Chlorophyll

Question 20

For what do the roots take up nitrates?

Answer 20

Amino acids

Question 21

Where are H+ ions stored in root cells?

Answer 21

The vacuole

Question 22

What do the protein pumps of root cells actively expel?

Answer 22

H+ ions

Question 23

What is the symplastic pathway?

Answer 23

water moves continuously through the cytoplasm of cells (connected via plasmodesmata)

Question 24

What is the apoplastic pathway?

Answer 24

water cannot cross the Casparian strip and is transferred to the cytoplasm of the endodermis

Question 25

What are halophytes?

Answer 25

plants that have adaptations to survive in environments of high salinity

Question 26

What are xerophytes?

Answer 26

plants that have adaptations to survive in dry conditions

Question 27

What adaptions do halophytes use to tolerate salty conditions?

Answer 27

Cellular sequestration Tissue partitioning Root level exclusion Salt excretion Altered flowering schedule

Question 28

What is cellular sequestration?

Answer 28

halophytes can sequester toxic ions and salts within the cell wall or vacuoles

Question 29

What is tissue partitioning?

Answer 29

plants may concentrate salts in particular leaves, which then drop off (abscission)

Question 30

What is root level exclusion?

Answer 30

plant roots may be structured to exclude ~95% of the salt in soil solutions

Question 31

What is salt excretion?

Answer 31

certain parts of the plant (e.g. stem) may contain salt glands which actively eliminate salt

Question 32

What is altered flowering schedule?

Answer 32

halophytes may flower at specific times (e.g. rainy seasons) to minimise salt exposure

Question 33

What are some adaptations that allow xerophytes to tolerate dry conditions?

Answer 33

Reduced leaves Rolled leaves Thick, waxy cuticle Stomata in pits Low growth CAM physiology

Question 34

What is the reason behind reducing leaves?

Answer 34

reducing the total number and size of leaves will reduce the surface area available for water loss

Question 35

What is the reason behind rolling leaves?

Answer 35

rolling up leaves reduces the exposure of stomata to the air and hence reduces evaporative water loss

Question 36

What is the reason for having a thick, waxy cuticle?

Answer 36

having leaves covered by a thickened cuticle prevents water loss from the leaf surface

Question 37

What is the reason for having stomata in pits?

Answer 37

having stomata in pits, surrounded by hairs, traps water vapour and hence reduces transpiration

Question 38

What is the reason behind low growth plants?

Answer 38

low growing plants are less exposed to wind and more likely to be shaded, reducing water loss

Question 39

What is the reason for CAM physiology?

Answer 39

plants with CAM physiology open their stomata at night, reducing water loss via evaporation