Topic 4 Flashcards
3 advantages of multicellularity
- division of labour: cells can become specialized to carry out functions
- size: organisms can be larger bc many cells work tgt to transport materials
- interdependence: organism is unaffected if a cells dies
shoot system
- stems, leaves, buds, fruits
- absorbs co2, releases o2
root system
- root & root hairs
- absorbs water & minerals from soil
meristems
- specialized cells, makes root & shoot tissue
- where mitosis occurs to increase size & repair damage
dermal tissue (epidermis) 5 points
- outer layer of cells for non woody plants
- gas exchange in leaves & lenticels (pores in woody stems&roots)
- protects plant from disease
- cuticle in leaves & stem: prevents water loss & microorganisms
- root: takes water & minerals from soil
ground tissue
- found in majority of plant, under epidermis
- leaves: location of photosynthesis
- stem: provides strength & support
- roots: food & water storage
vascular tissue
- transport of materials through plant
- xylem tissue: movement of water/dissolved minerals from roots to leaves
- phloem tissue: movement of sucrose/dissolved sugars from leaves to roots
guard cell
- specialized cells in dermal tissue
- controls shape of tiny pores (stomata) in leaves
- when guard cell is turgid (swollen): transpiration occurs & stomata opens to release o2 and absorb co2
stomata
allows gas exchange by diffusion, found under epidermis
what happens when plant is dehydrated
- turgor pressure decreases, guard cells shrink, stomata closes to save water
- slows down photosynthesis & may overheat
mesophyll
specialized cells in ground tissue
mesophyll type #1
palisade cells:
- long, rectangular cells tightly packed
- site of photosynthesis, has lots of chloroplasts
xylem
- thick walled tubes w/ cellulose & lignin
- these support cells in xylem by transporting water up from roots
mesophyll type #2
spongy mesophyll cells:
- irregular shape, loosely packed
- spaces allow gas exchange
phloem
- has individual sieve tube cells w end walls & connected to companion cells
- companion cells: directs sieve tube cells, allows transport of sugar
tropism
growth of plant in specific direction bc of a stimulus (causes an action)
positive tropism
growth of plant towards stimulus
negative tropism
growth of plant away from stimulus
phototropism
growth of plant in response to light (stems = pos tropism, roots = neg)
gravitropism
growth of plant in response to gravity (stems = neg, roots = pos)
auxin
- hormone controlling phototropism
- found in shady side of stem, causes it to grow to light source
transpiration
evaporation of water from plant
cohesion
- attraction b/w molecules of same substance
- water molecules stick tgt, pulls on each one in evaporation
adhesion
- attraction of 2 diff substances
- water sticks to xylem walls to keep gravity from pulling down
