plant growth and water transport

Question 1

what purpose does primary growth have?

Answer 1

lengthens plant at roots and shoots

Question 2

what are axillary/lateral buds?

Answer 2

buds that can form shoots, are dormant unless apical bud is damaged

Question 3

what are meristems?

Answer 3

portions of plant body that grow indefinitely, cells are undifferentiated and totipotent

Question 4

what are apical meristems?

Answer 4

meristems found at tips of roots and shoots
consists of protoderms (dermal tissue), ground meristems (ground tissue) and procambium (vascular tissue)

Question 5

from bottom to top, what are the three zones of plant growth?

Answer 5

zone 1 - cell division (meristems)
zone 2 - cell elongation and growth
zone 3 - cell maturation (root hair cells and differentiation)

Question 6

what do root caps do?

Answer 6

• protects root meristems
• allows root to move smoothly in soil
• senses gravity

Question 7

what is the purpose of secondary growth?

Answer 7

lateral (outward) growth, increases amount of conducting and structural tissue

Question 8

what are lenticles?

Answer 8

openings on bark for gas exchange

Question 9

what are the components of secondary phloem?

Answer 9

• sieve tubes
• companion cells
• sclerenchyma fibers

Question 10

what are the components of secondary xylem/wood?

Answer 10

• tracheids
• vessels
• parenchyma
• scelerenchyma fibers

Question 11

what is heartwood and what does it do?

Answer 11

• innermost, dark coloured xylem
• purely structural support (no water transport)
• produces resin

Question 12

what is sapwood and what does it do?

Answer 12

• outermost, light coloured xylem
• water transport

Question 13

what is solute potential?

Answer 13

• movement of water via osmosis
• high solute concentration = low solute potential
• always negative

Question 14

what is pressure potential?

Answer 14

• water movement in response to pressure
• opposite force to wall pressure and turgor pressure

Question 15

what is the difference between apoplastic, symplastic and transmembrane water routes?

Answer 15

symplastic = through plasmodesmata
apoplastic = through apoplast pores within cell wall
transmembrane = through aquaporins

Question 16

how does root pressure work?

Answer 16

• pressure potential drives water against gravity
• xylem water potential decreases, water from nearby cells is drawn in

Question 17

what steps cause stomata to open?

Answer 17

1) phototropins activate with blue light
2) proton pumps push out H ions
3) active transport of K and Cl through voltage pump and symporters
4) presense of K triggers conversion of starch into malate, increasing osmotic potential
5) water moves in via osmosis and guard cells inflate to open

Question 18

what steps cause stomata to close?

Answer 18

1) sugar concentrations decrease
2) guard cell solute concentration is less than surroundings, water moves out
3) guard cells become flaccid and close

Question 19

what are xerophytes and what are their adaptations?

Answer 19

• plants that evolved for dry conditions
• accumulates salt in roots to decrease solute potential
• lowers solute potential of leaves in summer
• thick waxy cuticle
• needle like leaves (lower SA and transpiration rate)
• stomata open at night