Plant Nutrition

by Ramneet Kaur
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Plant Nutrition

Plant nutrition includes elements of biological importance. Hydroponics is a technique of growing plants in a nutrient solution in absence of soil.

  • It was developed by Sachs and improved by Knopps.
  • It helps us to find out essential elements for plant growth.

Essential elements are elements which have a specific structural or physiological role and without which plants cannot complete their life cycle. There are 17 essential elements. Depending upon the quantity in which they are required by plants:

  1. Macronutrients: required > than 10m mole/kg of dry matter. They are C, H, O, N, S, P, K, Mg, & Ca.
  2. Micronutrients: required < than 10m mole/kg of dry matter. They are Zn, Mn, B, Cu, Mo, Cl, Ni & Fe.
Macronutrients:

C, H, O are non-mineral elements. They are building blocks of macromolecules that form the plant body.

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  • N, P, K are primary macronutrients.
  • Ca, Mg, S are secondary macronutrients.

Name of elementAbsorbed as:  Functions:
NitrogenNO3, NO2, NH4+Constituent of Proteins, Nucleic acids, Vitamins and Hormones, involved in metabolic activities.
Phosphorus H2PO4,        HPO42-Constituent of Cell membranes, Nucleic acids & Nucleotides, required for all phosphorylation.
Potassium KMaintains anion-cation balance, involved in protein synthesis, maintains turgidity in cell, helps in stomatal opening.
Calcium Ca2+Required for permeability of cell membrane, formation of mitotic spindle, formation of middle lamella.
Magnesium   Mg2+Constituent of chlorophyll, maintains structure of ribosomes, activates enzymes of photosynthesis & respiration, involved in DNA & RNA synthesis.
Sulphur  SO42-Constituents of amino acids – Methionine & Cysteine, Coenzymes, ferredoxin & Vitamins – Biotin, Thiamine & Coenzyme A.

Micronutrients:
Name of elementAbsorbed as:   Functions:
IronFe3+Involved in electron transport – ferredoxin & cytochromes activates catalase, essential for chlorophyll formation.
ManganeseMn2+Photolysis of water in photosynthesis, activates enzymes of photosynthesis, respiration & nitrogen metabolism.
 Zinc Zn2+Synthesis of auxin, RNA & protein, activates carboxylase.
 Copper Cu2+Component of plastocyanin & cytochrome oxidase, associated with redox enzymes.
 BoronBO33-, B4O72Required for uptake & utilization of Ca2+, membrane functioning, pollen germination, cell elongation & differentiation, carbohydrate translocation.
MolybdenumMoO22-Component of nitrogenase and nitrate reductase, Nitrogen metabolism.
ChlorineClAnion-cation balance, necessary for photolysis of water in photosynthesis.
NickelNi2+Constituent of urease, required for metabolism of urea and urides.

Critical concentration is the concentration of an essential element below which it retards plant growth. Moderate decrease in micronutrients causes deficiency symptoms and moderate increase causes toxicity. N, P, K & Mg are mobile elements and their deficiency symptoms first appear in older tissues while Fe, Zn, Mn, B, Cu, S, Ca are non-mobile and their deficiency symptoms first appear in young tissues.

Deficiency symptoms:
Deficiency Symptoms are:Deficiency due to:
Chlorosis – loss of chlorophyllN, K, Mg, S, Fe, Mn, Zn, Mo.
Necrosis – death of tissuesCa, Mg, Cu, K.
Inhibition of cell divisionK, N, Mo.
Delay in floweringN, S, Mo.
Stunted growthN, K, S, B, Zn, Mo, Cl, Ca,
Premature leaf fallP, Mg, Ca.

deficiency symptoms Non-essential elements required in metabolic activities of certain plants are cobalt, silica, sodium, aluminium, vanadium etc.

Non-essential elements required in metabolic activities of certain plants are cobalt, silica, sodium, aluminium, vanadium etc.

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