Explain with examples: macronutrients, micronutrients, beneficial nutrients, toxic elements and essential elements.
Explanation Macronutrients: These are the elements that are absorbed and stored in plant cells and tissues in large quantity i.e. in excess of 10mmole kg-1 of dry matter. These nutrients can be easily detected since they are present in large amount. 9 macronutrients are known till date. Function: Synthesis of organic molecules. Example: Carbon(C) Hydrogen (H2) Oxygen (O2) Nitrogen (N2) Phosphorous (P) Sulphur (S) Potassium (K) Calcium (Ca) Magnesium (Mg) Micronutrients: These are also called as trace elements. These elements are required by plants in very small amounts i.e. generally require less than 10mmole kg-1 of dry matter. They are difficult to detect and require modern, sophisticated techniques to determine their quantity. Function: Co-factor of enzymes Examples: Iron (Fe) Manganese (Mn) Copper (Cu) Molybdenum (Mo) Zinc (Zn) Boron (B) Chlorine (Cl) Nickel (Ni) Beneficial nutrients: These are the elements that are not essential but their presence in the plants is beneficial for improved metabolic activities. But, the in excess of these elements they become toxic to the plants. Function: Sodium (Na) Silicon (Si) Toxic element: These elements are toxic to the plants but can be beneficial if present in very low amounts. In presence of these elements the growth of plants is retarded. Example: Mn when present in excess concentration leads to deficiency of Fe, Mg, Ca Essential Elements: These elements are a must for the plant growth and can not be replaced with any other element i.e. non-replaceable. These elements are generally classified into macro and micronutrients. The deficiency of these elements leads to various health symptoms i.e. disease. Example: Nitrogen, Sulphur, Magnesium Final Answer Macronutrients: required in excess of 10mmole kg-1 of dry matter. e.g. C, H Micronutrients: less than 10mmole kg-1 of dry matter. e.g. Fe, Ni Beneficial nutrients: presence of these nutrients is not must but is beneficial if present. e.g. Na, Si Toxic element: toxic to the plants when present in excess. e.g. Mn when present in excess concentration leads to deficiency of Fe, Mg, Ca Essential elements: specific and non-replaceable. e.g. N, S, Mg
