nutrition and transport Flashcards
stomata
microscopic pore
gas exchange
about 90% plant water loss is through stomata
turgor
cannot take up more water
wilting
net water loss
transpiration
keeps plant cool
transport route:root to shoot
cooling prevents cellular damage to proteins, lipids and DNA
how do plants balance transpiration vs. CO2 uptake ?
environmental plasticity
regulation of the stomata (opening & closing)
genetic adaptions (c4 and CAM)
opening stomata
Swelling guard cells
closing stomata
shrinking guard cells
how do stomata take water in?
Potassium salt attracts water. Salt is lost to neighbouring cells, therefore water is lost and stomata shrink
stoma opening
change in membrane potential over membrane. Potassium uptake through K+ channels in membrane.
passive water uptake through aquaporins in membrane.
Swelling/shrinking= change in aperture
when is stoma mostly closed
in the dark (except CAM plants)
what regulates the stoma ?
the circadian clock
when do stoma open?
when internal CO2 is low
when do stoma close?
when turgor leaf decreases
chemiosmotics
leaf movements
how do plants get mineral nutrients ?
chemical elements absorbed from soil as inorganic ions
how much of the plants fresh weight is water ?
80-90%
how much of a pants dry weight is organic material?
96%
how much of a plants dry weight is inorganic material?
4%
Essential macronutrients
Carbon, oxygen, hydrogen, phosphorus, sulphur, potassium, calcium and magnesium.
essential micronutrients
Chlorine, iron, manganese, boron, zinc, copper, nickel, molybdenum
deficiency
below optimal
toxicity
super-optimal, too many essential nutrients
Nutrient uptake by roots
Absorption of nutrients in the root hair zone.
extensions of epidermal cells
large surface area
permeable epidermis
mycorrhizae
symbiotic structures made up of plant roots and fungal hyphae
Apoplast
Continuum formed by extracellular spaces in matrix of cells.
where is the apoplastic route blocked
endodermis
symplast
continuum of cytoplasm connected by plasmodesmata
selective uptake of nutrients into symplast
Channels selectively enable ions to cross membranes into cells.
membrane potential is driving force
inside cell more negative than outside
transporters and co-transporters of molecules
channels or channel proteins create a hydrophilic channel through the cell membrane, facilitating the transport of molecules down an electro -chemical gradient
endodermis
selective passage, barrier blocking apoplast
casparian strip
belt of waxy material
in cell walls of endodermal cells
blocks apoplastic route
forces water and nutrients through symplast.
stele
tissues inward from endodermis.
discharge of water and nutrients in vascular system
xylem
dead when functional
cell walls
what is the driving force of xylem transport
root pressure
transpirational pull
root pressure
osmotic forces create root pressure
high salt in stele
low salt in cortex
guttation
root pressure pushes excess water out through leaves
transpirational pull
creates negative pressure.
Cohesion between water molecules transmits pull from leaves to roots: hydrogen bonds, requires uninterrupted chain of water
phloem transport
transports sugars, amino acids and hormones. Main transport sugar is sucrose
Phloem flow from source to link
source: where sugar is produced
sink: consumer of sugar
phloem structure
sieve tube member, nucleus , companion cell and sieve plate
sieve tube
for transport. aligned, connected, connection sieve plate.
are alive but lack nucleus and ribosomes
companion cell
linked through plasmodesmata
mechanism of phloem transport
at source: sugar accumulation in sieve tube
passive uptake water
generation positive pressure.
at sink: sugar removal from sieve tube
passive loss water
decrease pressure
