Role of mineral elements and defieieney symptoms Maeronutrients

l. Carbon, Hydrogen and Oxygen:

Although these, elements are not minerals in the true sense, they are still included in the list as they are most essential for plant life. These three lements are also called framework elements.

These elements are involved in the synthesis of compounds like carbohydrates, fats, protein! Organic acids, enzymes, hormones etc in short they build up the protoplasm. Plants absorb them from air and soil in the form of carbondioxide and water. Deficiency of either water or carbon dioxide causes retradation of growth.

2. Nitrogen:

The sources of nitrogen are soil and atmosphere. Nitrogen is absorbed from the soil in the form of nitrates, nitrites and ammonium slats. Atmospheric nitrogen can be fixed and made available to the plant by certain bacteria.

Specific role (Function)

* It is important constituent of proteins, nucleic acids, porphyrins, alkaloids, some vitamins, co-enzymes and chlorophyll.

* Porphyrins are important part of chlorophylls and cytochromes.

Thus it plays very important role in metabolism, grwoth, reproduction and heredity. Deficiency symptoms:

* Nitrogen deficiency causes yellowing i.e. chlorosis of leaves. Older leaves are affected first.

* In some cases production and accumulation of anthocyanin pigment is found. As a result a purplish coloration appears in stems, petioles, and the lower leaf surfaces.

* Flowering is suppressed or delayed.

* Plant growth remains stunted.

3. Phosphorus:

It is present in the soil in inorganic and organic forms. It is absorbed primarily as the monovalent inorganic phosphate anions.

Specific role:

– It is a constituent of nucleic acids, phospholipids, NADP, ATP etc.

– Through nucleic acids and ATP it plays important role in protein synthesis.

– Phospholipids along with proteins form important constituents of cell membranes.

– Phosphorus is also an essential part of all the sugar phosphates in photosynthesis & other metabolic processes

– High amounts of phosphorus are found in the meristematic tissues.

Deficiency symptoms:

Phosphorus deficiency may cause premature leaf fall.

– Dead necrotic areas may be developed on the leaves, petioles or fruits.

– The plants show a general overall stunted appearance with often dark green coloration.

4. Potassium:

It is absorbed in the form of K/ ions from the soil. Specific Role:

* This element functions mostly as a catalytic agent in several enzymatic reactions.

* It is essential for translocation of sugar.

* Stomatal opening in higher plants requires potassium.

* It has a definite role in the regulation of water in plant cells.

* It helps in transport of ions across cell membrances.

* It maintains hydration, permeability and reactive state of protoplasm. Deficiency symptons:

– Mottled chlorosis of leaves occurs.

– Plant growth remains stunted with marked shortening of internodes.

– Potassium deficient cereal grains develop weak stalks and their roots become susceptibe to root rotting organisms..

5. Calcium:

It is absorbed as divalent Ca²⁺ from soil.

Specific role:

– It is required for the formation of calcium pectinate, which is the important constituent of middle lamella in cell wall.

– Calcium salt of lecithin, a lipid compound, is involved in the organisation of cell membrane.

– Calcium ions protect plants from the injurious effects of hydrogen ions, high salt concentration in the environment, and toxic effects of other ions in the environment.

– It serves as a cofactor or may act as an activator for certain enzymes like amylase, Atlases etc.

Deficiency symptoms:

– Calcium deficiency causes stem collapse and subsequent termination of growth in the apical meristematic regions of stem, leaf and root tips.

– Roots become short, stubby and brown.

– Chlorotic patches appear near the margin of younger leaves.

– The growing shoot tips is characteristic oi calcium deficient plants.

– Cell walls become rigid and brittle in calcium deficient plants.

6. Magnesium:

It is present in the soil in water soluble, exchangeable and fixed from.

Specific role:

– Magnesium is a component of the chlorophyll structure.

– It plays an important role in binding ribosomal particles during protein synthesis.

– The release of energy in the hydrolysis of high energy compounds like ATP is greatly influenced by Mg²\

Deficiency symptoms:

– Magnesium deficiency causes interveinal chlorosis of the leaves.

– Dead necrotic patches appear on the leaves.

– Anatomically magnesium deficiency causes extensive chlorenchyma development and scanty pith formation.

7. Sulphur:

Sulphur is taken up by the plants from the soil as divalent sulphate anions (S0₄ ²~).

Specific role:

– Sulphur is important constituent of some amino acids (Cystine, Cysteine, and Methionine)

– It is a constituent of biotin, thiamine, coenzyme A and lipoic acid which are involved in cellular metabolism.

– It is a constituent of volatile oils which give characteristic pungent adours to cruciferous plants.

– Disulphide linkages help to stabilize the protein structure.

– Sulfhydryl groups are necessary for the activity of many enzymes.

Deficiency symptoms:

– A deficiency of sulphur results in chlorosis or yellowing of the leaves. The younger leaves are affected first.

– Tips and margins of the leaf roll inward.

– Sulphur deficiency results in marked decrease of stroma lamellaae and an increase in grana stacking