Mineral Nutrition

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The toxicity symptoms are difficult to identify.Toxicity levels for an

element also vary for different plants.

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Excess of an element may inhibit the uptake of another element. Excess

of Mn induces deficiencies of Mg, Fe & Ca because it competes with Fe

& Mg for uptake and with Mg for binding with enzymes. Mn also inhibits

Ca translocation in shoot apex. Thus, symptoms of Mn toxicity may

actually be the deficiency symptoms of Fe, Mg and Ca. Main symptom

of manganese toxicity is the appearance of brown spots surrounded by

chlorotic veins.

MËÇHÅÑÏSM ØF ÅBSØRPTÏØÑ ØF ËLËMËÑTS

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The movement of ions is generally referred as flux.

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The inward movement of ions into the cells is called influx and the

outward movement is efflux.

The process of absorption includes 2 main phases:

First Phase: Initial rapid

and passive uptake of ions

into the apoplast (free

space or outer space)

of cells. It usually occurs

through ion-channels

(trans-membrane

proteins that function as

selective pores).

Second Phase: The ions

are taken in slowly into the

symplast (inner space or

cytoplasm) of the cells.

It is an active process

(requires energy).

TRÅÑSLØÇÅTÏØÑ ØF SØLÜTËS

01

Mineral salts are translocated through xylem

along with the ascending stream of water and

further taken by plants through transpiration pull.

02

Analysis of xylem sap shows the presence of mineral

salts in it. Use of radioisotopes of mineral elements also

proved that they are transported through the xylem.

SØÏL ÅS RËSËRVØÏR ØF ËSSËÑTÏÅL ËLËMËÑTS

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Weathering and breakdown of rocks enrich the soil with dissolved ions

and inorganic salts.