Solute Transport in Plant Cells Flashcards
What are plants?
Autotrophic
What does plants require?
- Sunlight
- CO2
- H2O
- mineral nutrients (from soil)
What are the essential nutrients?
- mineral elements from soil
What does the essential nutrients are for?
- plant growth
- reproduction
What are the inorganic ions in the soil?
- Anions
- Cations
What are anions?
negatively-charged
Cl-; NO3-; PO4 3-
What are cations?
positively-charged
K+; Na+; Ca2+; Mg2+
What happens of absence of essential nutrients?
- abnormalities in growth/reproduction
What great amounts are used by plants?
Macronutrients
What are macronutrients?
- nitrogen
- phosphorous
- potassium
- calcium
- magnesium
- sulfur
What are the remaining elements?
micronutrients
What are needed in very small amounts in plants?
micronutrients
What happens when essential elements are deficient in the soil?
plants exhibit deficiency symptoms
Why is nutrient availability important?
- soil properties
- plant requirements
What does every plant have?
optimal nutrient requirements
What if the plants are outside of optimum conditions?
plant deficiencies
plant toxicities
What are the mobile elemts?
- Nitrogen
- potassium
- magnesium
- phosphorus
- chlorine
- sodium
- zinc
- molybdenum
What are the immobile elements?
- calcium
- sulfur
- iron
- boron
- copper
What are the 3 soil phases?
solid, liquid, gaseous
What are the solids in the soil?
mix of mineral and organic matter
What are the percentage of the soil composition?
Air
Water
Mineral Matter
Organic Matter
Air - 25%
Water - 25%
Mineral Matter - 45%
Organic Matter - 5%
Do the ratios of solid, liquid and gas phases in soil change?
True or False?
True
When would soil change?
-wetting
-drying
-swelling
-shrinkage
-aggregation
-dispersion
-loosening
-compaction
-weathering (freeze-thaw cycles)
What are the chemical properties of soils?
6
- inorganic matter (sand, silt, clay)
- organic matter (humus)
- salinity and sodicity
- redox (oxidation/reduction)
- pH (buffering capacity)
- ion exchange (cation/anion exchange)
What does pH indicate in chemical soil?
degree of acidity or alkalinity of soils
What does pH impact in soil?
- ion mobility in soil
- available nutrient to plants
What does root growth favour?
pH 5-6.5
slightly acidic
Why is the range of the pH 5-6.5 important?
most essentail ions in the soil are available to plant roots
What is the link between metabolic processes and pH and ion exchange of soil?
- clay particles (- charged) binds to cations
- cations are exchanged for H ions from carbonic acid or form plant
- mineral cations are free into the soil solution
What is ion exchange?
measures amount of exchange between dissolved ions and surface soil particles
What ion exchange dominates in soils?
Cation Exchange capacity (CEC) dominates Anion exchange capacity (AEC)
- more negative charge than positive charge sites
What happens with soil with charged?
more + charged cations bind first and strongest
What happens with soil in raidus?
cations with smaller radius bind more strongly
What happens with availability in soil?
more abundant of cations bind more readily
What does mobility of elements in soils determine in plants?
- where nutrients are found in soil
- what zones in soils will become depleted
- need for supplements (fertilizers)
What is the sorption zone with mobile nutrients?
larger
What is the sorption zone for immobile nutrients?
smaller
What does root growth help?
nutrient acquisition
what do roots obtain?
water and minerals
how do roots obtain water and minerals ?
develop extensive root systems
where are the roots located at?
apical meristem
what growth does roots have?
continuous growth
what develops quickly in the roots?
extensive root systems - high surface area
describe roots movement in soil
flexible architecture
What is the characteristic of the root transport systems?
high affinity membrane transport systems
What is affinity?
Attraction between molecules like enzymes, substrates, antibodies and antigen
Where is the root growth found in?
rhizosphere (root zone)
What is rhizosphere?
region of soil surrounded by roots
Where does radial (lateral) transport from . . . to . . .
from root hairs to root xylem
where does the nutrients travel into?
roots through both apoplastic route and symplastic route
What is the process of the nutrients/minerals?
dissolved in water that moves from soil into root tissues to the xylem transport everywhere in plant
- water potential gradient
what is the membrane called when cells separated from environment
plasma membrane
What condition does the inside cell have?
constant conditions
What condition does the outside cell have?
highly variable conditions
What does the plasma membrane do?
control in and out traffic of ions and molecules
what are the roles of the cells?
cells take up nutrient & water, export wastes
what does transport do in plant cells?
- molecular, ionic movement
- between inside and outside cell
- between cellular compartments
at what levels does nutrient transport happen in plant cells?
- cell membrane
- between cell and external environment
- between different plant parts
where does all transport processes happen?
cell level
In special case of charged ions/molecules and membranes:
What can the membranes do?
differentially permeable to ions
What do the ions do?
diffuse independently
What do ions diffuse in response to?
- concentration gradient = diffusion potential
- electrical charge differences = electrical potential
True or False
Can ions be driven passively against the concentration gradient if appropriate voltage is applied?
True
What is driving forces controlled by?
Electrochemical potential/ membrane potential
+
concentration gradient differences with differences of electrical charge
What do plants use to generate electrochemical potentials?
proton pumps
What do plants use to generate using proton pumps?
Electrochemical potentials
What happens with cation proton pumps to generate electrochemical potentials?
cations (K+) from extracellular fluid go into cytoplasm using membrane potential
What happens with anion proton pumps to generate electrochemical potentials?
anions (Cl-, NO3-) are taken into cytoplasm by coupling their transport to the inward diffusion of H+ through cotransporter (= symport protein)
What happens with neutral solute proton pumps to generate electrochemical potentials?
neutral solute (e.g. sugar) extracellular fluid to cytoplasm coupling to facilitated proton diffusion using cotransport (= symport protein)
What is symport protein?
transport for two or more molecules across membrane in same direction
what to use transport across cell membrane?
electrochemical gradient
Which membrane is more permeable and to what?
biological membranes
to ions, large polar molecules, and water
membrane permeability depend on?
- characteristics of membrane
- chemical nature of substance
what does membrane do to diffusion?
slows diffusion, but still reaches equilibrium
What are the two components of membrane permeability?
- diffusion potential
- electrogenic transport
What is diffusion potential?
ions diffuse across membrane independently to the concentration gradients
what happens to the result of diffusion potential?
charge separation across the membrane
how is electrogenic transport measured?
membrane potential
what is electrogenic transport?
difference in electrical charge across membrane
charge distribution is uneven
what happens when membrane is equally permeable to anions and cations?
no membrane potential
E(mV) = 0
what odes no membrane potential mean?
membrane equally permeable to anions and cations
what happens when permeability differs?
charge separation
E (mV) = + or -
what do we use Nernst Equation for?
predictive model of membrane potential
- electrical potential difference across membrane
- deals with only 1 ion with K+
what if 10x concentration outside to inside?
+59 mV
what if 10x concentration inside to outside?
-59 mV
what is the animal cells membrane potential nernst equation predict?
-80 mV to -40 mV
what are the plasma membrane potential for plants?
more -ve
~ -130 mV to -110 mV
how come there are difference presence in membrane potential?
due to H+- ATPase pumps (proton pumps)
what are the differences of membrane potential for?
- ATP to pump H+ out of cytosol
- help maintain pH of cytosol (neutral pH for enzyme cell function)
What is apoplast?
proton pump transport H+ from cytosol to cell wall
What is symplast?
proton pump transport H+ from cytosol to vacuole
What does Nernst Eqn help distinguish?
active and passive transport
What are the active transport ?
transported out of cytosol
Na+, Mg2+, Ca2+
What are the passive transport?
transported into cytosol
NO3-, Cl-, H2PO4-. SO4^2-
how are anions moving of cytosol?
in
how are cations moving of cytosol?
out
how are K+ moving ?
passively in cytosol & vacuole
how and when are K+ taken up?
actively; when internal K+ are low
what and when happens to the movement of H+?
actively removed from cytosol to apoplast & to vacuole
what and where are cations (Na+, Ca2+) movement?
actively removed from cytosol to apoplast & to vacuole
what and where are anions (Cl-, NO3-, H2PO4-) movement?
actively accumulated into cytosol from external medium & from vacuole
where does the water and nutrient ions move thru?
- apoplast
- symplast
what does symplastic transport use?
plasmodesmata
what does living cells use?
differential membrane potential for different ions to move ions/molecules into/ out of cells
change solute potentials & water potentials
what does plasmodesmata control?
seize of ions/molecules transported form cell to cell using the Size Exclusion Limit
What is allowed in the plasmodesmata?
water, ions & small molecules
what are not allowed thru plasmodesmata?
large molecules
what does xylem loading involve?
transport of ion from symplast into tracheids/vessel elements
what is the criteria of water and solutes (ions, molecules)?
cross minimum of 2 plasma membranes during xylem loading in roots –> bc Casparian strip
what happens to the solute transport during xylem loading?
highly regulated in root stele (vascular tissue)
which places involves p+ pumps?
plasma membranes & both passive & active transport across the plasma membranes & the vacuole to noplast
