Mineral Nutrition:

The study of source, mode of absorption, distribution and metabolism of various inorganic substances or minerals by plants for their growth, development, structure, physiology and reproduction.

Autotrophs:

Organisms which use inorganic source of carbon i.e., CO2, Two types:

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(a) Photoautotrophs (photosynthetic):

Use light energy e.g., all green plants, blue green algae, green and purple sulphur bacteria.

(b) Chemoautotrophs (chemosynthetic):

Use chemical energy e.g., Nitrosomonas, Nitrosococcus and some other nitrogen cycle bacteria.

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Heterotrophs:

Organisms which depend upon organic sources of carbon. Two types-

(a) Photohetrotrophs:

Use light energy e.g., some purple nonsulphur bacteria.

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(b) Chemoheterotrophs:

Use chemical energy e.g., all animals, fungi, most bacteria and some flowering plants.

Essential Mineral Elements :

i. Such elements without which the plant cannot complete its life cycle.

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ii. Arnon and Stout (1939) proposed criteria of essentiality of an element i.e., the element must be directly involved in the nutrition of plant, must be absolutely necessary for supporting nornla! growth and reproduction and the requirement must be specific and not replaceable by another element.

iii. Based on the quantity in which they are required by plants:

(a) Macro nutrients (major elements):

Required by plants in quantity of more than 1 milligram/gram dry matter. Total 9 in number-C, H, O, N, P, K, S, Mg and Ca.

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(b) Micro nutrients (Micro or minor or rare or trace elements):

Required by plants in quantity less than 1 milligram/gram of dry matter. Total 8 in number-Fe, Mn, Zn, Cu, Mo, B, CI and Ni.

Sources of essential elements for plants:

Carbon:

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As atmospheric carbon dioxide

Hydrogen:

Mainly in the form of water.

Oxygen:

From the air or water or in the form of inorganic ions.

Nitrogen:

Absorbed by plants is the form of nitrate from the soil. Nitrogen fixers (organisms) convert nitrogen gas (N2) to anionic forms such as nitrate (NO3 –) or nitrite (NO2-) or a reduced cationic form such as ammonium (NH4 +). These compounds enter plants through the root and are assimilated as organic nitrogen.

Other elements:

Absorbed from the soil e.g., phosphorus as phosphates and sulphur as sulphate etc.