Download MECHANISM of MINERAL SALTS ABSORPTION

MECHANISM of MINERAL SALTS
ABSORPTION
In addition to carbon, hydrogen and oxygen,
plant needs essential elements absorbed by
roots, deficiency in these elements leads
to:
Disturbance or stop in plant growth,
No flowers
No fruits
They are two groups :
1) MACRO - NUTRIENT :
7 , needed in considerable amounts ,
(Mg - I - S - Ph - N - Ca - and K)
2) MICRO - NUTRIENT :
8, needed in very small amounts, mg/liter,
they activate enzymes, copper, iodine,
zinc, molybdenum, aluminum, boron, chlorine
and manganese.
Mechanism :
1)Ionic diffusion :
solutes in the soil are either positive
ions , cations ( K and Ca ) or negative
ions , anions ( SO4 , NO3 , and Cl ) ,
they behave independently of each other
and of water .
They move by diffusion from soil solution
through the wet cellulose walls .
Under certain conditions CATIONS EXCHANGE
may take place, Na ions get out and
replaced by K ions.
2) Selectively permeability
when ions reach semipermeable cell
membrane, some are selected ( required by
the plant ) and pass inwards , while
others are not , regardless their sizes ,
concentrations and charges .
3) Active Transport
is the passage of substances through cell
membrane by the help of chemical energy
supplied during respiration of root
tissues , that move these ions against
concentration gradient .
EXPERIMENT was done on NITELLA
ALGA that lives in Swamps :
A) concentration of ions in its cell sap
is higher than in swamp indicating that
the cell use some energy to absorb these
ions .
B) concentration of ions is variable ,
some are higher than others , indicating
that ions are selectively absorbed
according to cell requirement .
NOTE : Aerobic Respiration needs the
presence of sugar and oxygen which are
essential to absorb salts by active
transport .
EXPERIMENT on BARLEY plant to show the
effect of the presence or absence of
Oxygen on absorption of sulphate ions
:
Barley plant was supplied with sulphate
ions SO4 , containing radio active
sulphur .
Absorbed sulphates was estimated by using
" Geiger Counter " in aerobic and in
anaerobic conditions .
Observations : absorption of sulphate
ions was less in anaerobic than in
aerobic conditions .
Conclusion : active transport helps ions
absorbed by plant cells using energy
produced during aerobic respiration .