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:
- Macronutrients: required > than 10m mole/kg of dry matter. They are C, H, O, N, S, P, K, Mg, & Ca.
- Micronutrients: required < than 10m mole/kg of dry matter. They are Zn, Mn, B, Cu, Mo, Cl, Ni & Fe.
C, H, O are non-mineral elements. They are building blocks of macromolecules that form the plant body.
- N, P, K are primary macronutrients.
- Ca, Mg, S are secondary macronutrients.
|Name of element||Absorbed as:||Functions:|
|Nitrogen||NO3–, 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||K||Maintains 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.|