Plant Structure and Function Chapter 29 Flashcards
land plants are a __ group that includes __ and __
monophyletic; vascular plants; bryophytes
all land plants are descended from
green algae
two types of land plants
bryophytes; vascular plants
vascular plants can
pull water from the soil
bryophytes
cannot pull water from the soil
first plant groups to diverge
mosses, liverworts, hornworts
-need water to photosynthesize
more than 95% of plants today are
vascular plants
4 kinds of vascular plants
ferns and horsetails, angiosperms, gymnosperms, lycophytes
bryophytes exhibit
desiccation tolerance
which structures of a plant form the shoot?
leaves
stems
reproductive organs
what is the principal site of photosynthesis in vascular plants?
leaf
what are the leaf’s 3 major tissues top to bottom?
epidermis
mesophyll
veins
CO2 uptake results in
water loss
the leaf’s air spaces are connected to the air surrounding the leaf by __
pores in the epidermis
photosynthesis ___ the concentration of __ _molecules w/n the leaf’s air spaces relative to the concentration of ___ in the outside air, the difference in concentration between the inside and the outside of the leaf causes __ to ___ into the leaf which ___
lower; CO2; CO2; CO2; diffuse; replenishes the supply of CO2 for photosynthesis
rate of water vs CO2
water vapor diffuses out of a leaf at a much faster rate than CO2 diffuses inward
transpiration
the loss of water vapor from leaves
how can vascular plants sustain such high rates of water loss?
b/c they can access the soil
the __ restricts water loss from leaves but inhibits the uptake of CO2
cuticle
__ cells secrete a waxy cuticle
epidermal
stomata
small pores in epidermis that allow CO2 to diffuse in
can open and close
help to regulate water loss
each stoma consists of two
guard cells
an increases in solute concentration causes water to
flow into the cell by osmosis, so water molecule concentration decrease
stomata also respond to
light (opens)
high levels CO2 (closes)
signaling molecules
CAM plants use ___ to avoid water loss during the day
nocturnal CO2 storage
what is the storage form of CO2 and how is it created?
produced by enzyme PEP carboxylase
combines dissolved form of CO2 w/ 3 carbon compound called PEP
results in 4 carbon organic acid stored in cell’s vacuole
for CAM plants, when the sun comes up, what happens?
stomata close
4 carbon organic acids retrieved and transferred to chloroplasts
they are decarboxylated (their CO2 is released)
now incorporated into carbs by the calvin cycle
the 3 carbon PEP converted into starch & stored in chloroplast til sun goes down
by opening stomata only at night, CAM plants…
greatly increase the amount of CO2 gain per unit of water loss
what is the drawback of CAM?
carb production is slower
C4 plants suppress photorespiration by
concentrating CO2 in bundle-sheath cells
photorespiration
when O2 is the substrate on rubisco and there is a net energy loss and release of CO2
why does temperature have a major effect on photorespiration?
because the selectivity of rubisco for CO2 over O2 is reduced as temperatures increase
both CAM and C4 plants produce ___. However, …
4 carbon organic acids as the entry point for photosynthesis. in CAM plants, CO2 capture and the calvin cycle happen at different times; in C4 plants, they take place in different cells
C4 plants capture __ in ____ cells by means of __. This produces 4 carbon organic acids that diffuse through __ into the ___.
CO2; mesophyll; PEP carboxylase; plasmodesmata; bundle sheath
what is the significance of the C4 cycle?
much faster than calvin cycle bc of the very low catalytic rate of rubisco so this means CO2 concentration in the bundle sheath cells is super higch
THIS MAKES IT UNLIKELY THAT RUBISCO WILL TAKE O2 TO THE DANCE
C4 plants lose less water
C4 plants have an advantage where?
sunny, hot environments
-tropical grasses, corn, sugarcane
disadvantage of C4?
greater energy requirement than conventional C3 photosynthesis bc ATP must be used to regenerate PEP in the C4 cycle
phloem
transports carbs from leaves to the rest of the body
xylem
inner tissue
transports water from the roots to the leaves
xylem provides a ___
low-resistance pathway for the movement of water
walls of xylem conduits are __ and contain ___
thick; lignin
how does water enter and exit xylem conduits?
through pits
unicellular conduits are called
tracheids
multicellular conduits are called
vessels (made up of vessel elements)
water in xylem first enters through ___ and travels up through the ___ and then flow outward through other___ into an adjacent, ___
pits; conduit interior; pits; tracheid
___ are the principal conduit in angiosperms
vessels
water is pulled through xylem by an ____
evaporative pump
how does the evaporative pump work?
stomata open, water evaporates from walls of cells
dehydration of cell walls creates force that pulls water toward sites of evaporation
force goes through xylem, beginning in leaf veins & then down through the stem and out through the roots to the soil
water can be pulled through xylem because of the
strong hydrogen bonds that form between water molecules
xylem transport is at risk of
conduit collapse and cavitation
cavitation can occur by
an air bubble being pulled through a pit bc of lower pressure in water compared to air (happens during drought)
gases coming out of solution during freezing (angiosperms susceptible to this)
how does the xylem protect against cavitation?
having many conduits in parallel
phloem is capable of
moving carbs efficiently across the entire length of a plant
phloem transports carbs from __ to __
sources (regions that produce or store carbs) to sinks (any part of the plant that needs carbs to fuel growth/respiration)
3 parts of phloem
sieve element
companion cells
plasmodesmata
water can travel from sieve tubes to
xylem
in angiosperms, sugar transport occurs through __
sieve plates
phloem not only transports carbs, but …
RNA, protein signals, hormones, nitrogen, ions
how are carbs pushed through phloem?
by an osmotic pump
how does the osmotic pump work w/ phloem?
the different in turgor pressure
high concentration in source, low in sinks
a fraction of the carbs transported to the roots spills out into the ___
rhizosphere
the ____ allows the root to control what solutes enter the xylem. how?
casparian strip
solutes pass thru plasma mem. via atp powered protein complexes that restrict certain compounds through endodermis
xylem and phloem are located at the center of the root and are surrounded by the
endodermis
why are plants harmed by flooding?
waterlogged soils slow down the diffusion of oxygen, which limits respiration
when transpiration rates are high, the ___ helps to get nutrients to root
flow of water through the soil
roots can release __ to make the environment around them more ___
protons; acidic
___ are symbioses between roots & fungi that increase nutrient uptake
mycorrhizae
plant gives carbs, fungus gives nutrients
endomycorhizae enhance ___ uptake
ectomycorrhizal enhance __ uptake
phosphorus; nitrogen
what do bacteria do for plants?
since plants need nitrogen, the bacteria through nitrogen fixation take nitrogen and transform it into NH3 and put it into the soil so plants can use it to build proteins
how do we preserve nitrogen in the soil?
crop rotation, specifically legume rotation
industrial fixation of nitrogen w/ fertilizer
