plant growth and water transport Flashcards
what purpose does primary growth have?
lengthens plant at roots and shoots
what are axillary/lateral buds?
buds that can form shoots, are dormant unless apical bud is damaged
what are meristems?
portions of plant body that grow indefinitely, cells are undifferentiated and totipotent
what are apical meristems?
meristems found at tips of roots and shoots
consists of protoderms (dermal tissue), ground meristems (ground tissue) and procambium (vascular tissue)
from bottom to top, what are the three zones of plant growth?
zone 1 - cell division (meristems)
zone 2 - cell elongation and growth
zone 3 - cell maturation (root hair cells and differentiation)
what do root caps do?
- protects root meristems
- allows root to move smoothly in soil
- senses gravity
what is the purpose of secondary growth?
lateral (outward) growth, increases amount of conducting and structural tissue
what are lenticles?
openings on bark for gas exchange
what are the components of secondary phloem?
- sieve tubes
- companion cells
- sclerenchyma fibers
what are the components of secondary xylem/wood?
- tracheids
- vessels
- parenchyma
- scelerenchyma fibers
what is heartwood and what does it do?
- innermost, dark coloured xylem
- purely structural support (no water transport)
- produces resin
what is sapwood and what does it do?
- outermost, light coloured xylem
- water transport
what is solute potential?
- movement of water via osmosis
- high solute concentration = low solute potential
- always negative
what is pressure potential?
- water movement in response to pressure
- opposite force to wall pressure and turgor pressure
what is the difference between apoplastic, symplastic and transmembrane water routes?
symplastic = through plasmodesmata
apoplastic = through apoplast pores within cell wall
transmembrane = through aquaporins
how does root pressure work?
- pressure potential drives water against gravity
- xylem water potential decreases, water from nearby cells is drawn in
what steps cause stomata to open?
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
what steps cause stomata to close?
1) sugar concentrations decrease
2) guard cell solute concentration is less than surroundings, water moves out
3) guard cells become flaccid and close
what are xerophytes and what are their adaptations?
- 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
