Ion traffic into roots

1. Nabgha nosheen
1375

2. Ion traffic into
roots

3. What are essential elements?
There are 113 or so different elements in this
planet, of which fourteen or fifteen are
absolutely required for the life processes
without which plants exhibit diseased
symptoms and ultimately die.

4. eight elements are required in sufficient
quantities----macronutrients
other in small quantities -----
micronutrients
The macronutrients are carbon, hydrogen, nitrogen,
phosphorus, potassium, calcium, sulphur, magnesium
and iron.
The micronutrients are manganese, zinc, boron,
copper, molybdenum and cobalt.

5. plants also contain elements other than
the macro and microelements ----- non
essential elements.
These are sodium, aluminum, silicon,
chlorine, gallium, etc.,

6. Sources of nutrients
Atmosphere water soil

7. Most of the above said
elements are found in soil
solution either in the form of
inorganic or organic salts or
ions; which may exist in either
in free state or bound to clay
particles

8. Whenever there is depletion of any
free ions from the soil solution,
respective ions are released from clay
particles into the soil solution to
maintain the equilibrium. This is
achieved by a process called
ion exchange process

9. Ion exchange
Process
1. contact ion
exchange
mechanism
2. carbonic acid
ion exchange
mechanism

10. CONTACT ION EXCHANGE MECHANISM
Plant roots are in contact with soil clay
particulates which have colloidal dimensions,
Root cells which are living, secrets hydrogen
ions which are positively charged and have
greater affinity so it can easily displace cations
like K+, Na+ ions that are bound to clay
particulates. Thus the cations are made
available for the root system to absorb the
required ion.

11. Cationexchange

12. CARBONIC ACID ION EXCHANGE MECHANISM
҉ Roots continuously respire irrespective of day or
night, and liberate significant quantities of CO2,
which when dissolved in soil water produces
carbonic acids. Immediately they ionize into H+ and
bicarbonate ions (HCO3).
҉similarly organic matter also has negative charge
– phenolic group ionize—carboxyl group ionize into
coo- and H+ , and hydroxyl group(-OH)
into O- and H+.

13. ION EXCHANGE MECHANISM
Cation exchange
Anion exchange

14. ҉ Clay mineral fraction is abundant in soil.
҉ Clay largely consist of Si4+ & Al3+
҉ Si4+ and Al3+ Mg2+ and Fe2+
҉ Such replacement results in availability of negative sites on
clay particles so that dissolved cations adsorbed on their
surfaces.
Cation exchange

15. Anionexchange
҉ Mineral anions are usually repelled by –tv charge of
clay.
҉ anion exchange capacity is usually smaller than the
cations.
҉ common anions are phosphate(PO4),nitrate(NO3
-),
sulfate (SO3
2-) and chloride (Cl-).
҉ because of this repulsion they leached out from soil.

16. SoilpH
҉ pH can effect the growth of plant root and
microorganism ----- favoured by slightly acidic pH values.
҉ pH determines availability of plant nutrients-----pH
favors weathering of rocks—release K+,Mg+,Ca2+ and
Mn2+.
҉ Low pH increase solubility of the salts and their
absorption by roots------salts such as CO3
2-, SO4
2-, PO4
3-
etc.

17. Three ways dissolved minerals moves through root hairs
1) Apoplast: dissolved minerals
moves through cell walls and
never enter cells
2) Symplast: it moves from one
cell to another through the
cytoplasm
3) Transmembrane: repeatedly
moves back and forth from
cell wall, crossing the
membrane, and through the
cytoplasm(vacuolar)
apoplastic
symplastic

18. Pathway of dissolved minerals Movement
1) Uptake via root hairs
2) travels via apoplast or symplast
through the cortex until it
reaches the endodermis that
lines the vascular cylinder
(stele).
3) Endodermis has a “casparian
strip”, a selectively waxy layer,
which BLOCKS the apoplast
pathway, so water MUST move
into the stele via symplast (to
regulate what minerals in the
water can enter the stele)
4) Xylem within the stele
transports water to shoots

19. Mechanism of transport