Biology II Exam #2
4 major types of plant organ systems
1. reproductive organs
2. leaf
3. stem
4. roots
why are vascular plants better able to sustain photosynthesis than
bryophytes?
vascular plants have root systems that help them take up water from
the ground
- water is needed for photosynthesis
- bryophytes (nonvascular) can only rely on water on the surface
where does photosynthesis occur?
leaf of a plant
transpiration
loss of water vapor from leaves
why do plants transpire?
CO2 uptake --> carbon atoms used to produce carbohydrates in Calvin
Cycle --> results in water loss
why are transpiration rates very high?
the water vapor concentration gradient
- CO2 concentration difference driving the diffusion of CO2 into the leaf
is much smaller than the concentration difference driving the diffusion
of water out of the cell
3 major tissues of the leaf
,1. dermal tissue
2. ground tissue
3. vascular tissue
example of dermal tissue
epidermis
epidermis
outermost layer of cells
example of ground tissue
mesophyll
mesophyll
tissue of loosely packed photosynthetic cells
example of vascular tissue
xylem, phloem
veins
system of vascular conduits within the leaf
how do plants sustain such high rates of water loss?
by obtaining water from the soil
2 structures that help minimize water loss
1. stomata
2. waxy cuticle
stomata
pores in the epidermis
- allows gasses to diffuse into/out of the leaf
, - compromises b/n minimizing water loss & providing CO2 uptake
- open/closes to maintain water balance
guard cells
two cells that surround central pore of stomata
- stomata opens, guard cells swell & pump in solutes --> water
diffuses in through osmosis
- stomata closes, guard cells shrink & pump out solutes --> water
diffuses out through osmosis
waxy cuticle
waterproof layer to stop water loss due to photosynthesis
3 types of photosynthesis
1. C3
2. CAM
3. C4
C3 plants
plants that use the Calvin Cycle for the initial steps of photosynthesis
that incorporate CO2 into carbohydrates
- no separation of initial carbon fixation & Calvin Cycle
- 85% of plants
where does the "C3" come from?
3-carbon molecule (3-PGA) that is produced from the Calvin Cycle
CAM plants
plants that store CO2 (open stomata) at night to avoid water loss, close
stomata during the day
4 major types of plant organ systems
1. reproductive organs
2. leaf
3. stem
4. roots
why are vascular plants better able to sustain photosynthesis than
bryophytes?
vascular plants have root systems that help them take up water from
the ground
- water is needed for photosynthesis
- bryophytes (nonvascular) can only rely on water on the surface
where does photosynthesis occur?
leaf of a plant
transpiration
loss of water vapor from leaves
why do plants transpire?
CO2 uptake --> carbon atoms used to produce carbohydrates in Calvin
Cycle --> results in water loss
why are transpiration rates very high?
the water vapor concentration gradient
- CO2 concentration difference driving the diffusion of CO2 into the leaf
is much smaller than the concentration difference driving the diffusion
of water out of the cell
3 major tissues of the leaf
,1. dermal tissue
2. ground tissue
3. vascular tissue
example of dermal tissue
epidermis
epidermis
outermost layer of cells
example of ground tissue
mesophyll
mesophyll
tissue of loosely packed photosynthetic cells
example of vascular tissue
xylem, phloem
veins
system of vascular conduits within the leaf
how do plants sustain such high rates of water loss?
by obtaining water from the soil
2 structures that help minimize water loss
1. stomata
2. waxy cuticle
stomata
pores in the epidermis
- allows gasses to diffuse into/out of the leaf
, - compromises b/n minimizing water loss & providing CO2 uptake
- open/closes to maintain water balance
guard cells
two cells that surround central pore of stomata
- stomata opens, guard cells swell & pump in solutes --> water
diffuses in through osmosis
- stomata closes, guard cells shrink & pump out solutes --> water
diffuses out through osmosis
waxy cuticle
waterproof layer to stop water loss due to photosynthesis
3 types of photosynthesis
1. C3
2. CAM
3. C4
C3 plants
plants that use the Calvin Cycle for the initial steps of photosynthesis
that incorporate CO2 into carbohydrates
- no separation of initial carbon fixation & Calvin Cycle
- 85% of plants
where does the "C3" come from?
3-carbon molecule (3-PGA) that is produced from the Calvin Cycle
CAM plants
plants that store CO2 (open stomata) at night to avoid water loss, close
stomata during the day
