Plant biology 2 Flashcards
what do amphistomatous and hypostomatous mean?
stomata on the upper AND lower leaf
stomata on just the lower leaf
what are stomata sensitive to? (6 things)
light intensity temperature water deficit atmospheric CO2 air pollution touch
who said that stomatal opening was controlled by turgidity of guard cells relative to surrounding subsidiary cells?
von mohl - 1856
what does the diffusive capacity of leaves represent?
product of stomatal number and stomatal aperture
what is the endogenous circadian rhythm?
stomatal opening and closing over the course of the day under constant environmental conditions
what is triggered in soil water deficit?
abscisic acid (ABA)
what increases the opening of stomata?
guard cell turgor from active loading of guard cells with K+ (from the walls of surrounding epidermal cells)
K+ uptake also drives the osmotic uptake of water
distortion of what what causes stomata to open?
guard cells
what 6 reasons make water good for sustaining life?
stable liquid in a range of temperatures good solvent transparent to visible light generates pressure (turgor) molecules show mutual attraction and are attracted to surfaces
what is the most active region of a plant?
root hair zone
what blocks the apoplast pathway?
casparian strip
how does water move through the symplast pathway?
between cytoplasm/vacuoles of adjacent cells
what are the two types of tracheary elements and which one is longer?
tracheids are < 3mm long
vessel elements are 4 - 300cm in length
what is the direction of water movement determined by?
the value of water potential in the adjacent cell
which direction will water move?
to the area of decreasing water potential
what does it mean by cohesion and tension?
water molecules exhibit strong mutual attraction from hydrogen bonding leading to cohesion between molecules, this creates tension that pulls water in a column up the xylem
what 2 methods help pull water up the xylem?
capillary action
root pressure - movement of water through root ‘pushes’ water up xylem aiding ‘pull’ created by cohesion-tension
what is cavitation?
tension on water column in xylem causes dissolved gases to come out of solution creating microscopic bubbles that coalesce and fill conduit
what is embolism?
cavitation bubbles obstruct passage of water in affected tracheids and vessels
when do stomata close to protect leaf against desiccation?
water stress
who said that ‘plants obtain a portion of their nutrition from the air when light is involved’?
stephen hales
what did julius mayer deduce?
that energy used by green plant tissue was derived form the sun and that plants were capable of of transforming radiant energy to chemical form
where does the light dependent reaction of photosynthesis take place and what are the products?
thylakoid membranes
ATP and NADPH
where does the reactions of the calvin cycle take place?
in the stroma
what were the earliest forms of photosynthetic organisms called?
stromatolites
when did photosynthetic diversity evolve?
carboniferous era, 300mya
what enzymes catalyse the C4 pathways?
PPDK, PEPC
what is the difference in structure of C3 and C4 plants?
C4 leaves have kranz anatomy - spongy mesophyll cells clustered in a ring around the leaf veins outside bundle sheath cells
what percentage of plants are CAM plants?
7%
what percentage of plants are C4 plants?
2%
what are features of CAM plants?
overnight accumulation of acids in vacuole
inverted stomatal rhythm
adaptation to drought
what pigments are in higher plants?
a + b
what pigment is in diatoms?
c
what pigments are in red algae?
d
chlorophyll a + b are only specific to certain wavelengths, what fills the gap?
carotenoids
what adaptations do sun leaves have? (4 things)
many cell layers
tightly packed cells
less grana stacking
orientated away from sun
what adaptations do shade leaves have?
few cell layers
lots of air space
more granal stacking
orientated towards sun
what are the temperature ranges do psychrophiles, mesophiles and thermophiles have?
psychrophiles - 0 - 10 degrees
mesophiles - 10 - 30 degrees
thermophiles - 30 - 65 degrees
what is the definition of stress?
an adverse force/influence that tends to inhibit ‘normal’ systems from functioning
what is the difference between adaptation and acclimatisation?
adaptation is heritable, acclimatisation is not
what are the symptoms of chill injury?
reduced photosynthesis and protein synthesis
damage to cell membranes
impaired protoplasmic streaming
which fatty acids exhibit lower transition temperatures?
unsaturated fatty acids
freezing stress causes what?
ice damages to membranes
what does it mean when water vitrifies?
solidifies without forming ice crystals - does not damage the membrane
what adaptations do plants have to avoid high temperature stress? (3 things)
leaf rolling
leaf hairs
increased wax on leaf surface to reflect light
what is the definition of water potential of a solution?
the difference in free energy level between that of pure water and that of a solution
what is water potential measured in?
mPa
what are xerophytes?
plants adapted to dry conditions
what adaptations of xerophytes have? (5 things)
stomatal crypts CAM photosynthesis spines not leaves succulence extensive but shallow root systems
what controls flux of water vapour from leaf to atmosphere
stomatal conductance
what is vapour pressure deficit? (VPD)
difference between vapour pressure of bulk air and saturated vapour pressure in in sub stomatal cavity
if the VPD is high what does this mean?
the more drought stressed the plant is
what is the current CO2 level in the atmosphere?
408ppm
what is the current O3 level in the atmosphere?
40ppb
what does ozone trigger in a plant?
ethylene production which reduces stomatal sensitivity to abscisic acid therefore affecting a plants capacity to regulate its water balance
how much is the Quelccaya glacier shrinking?
600ft per year
at what temperature does coral bleaching occur?
above 85F
what will melting permafrost release?
methane
