Explain with examples:macronutrients, micronutrients, beneficial nutrients, toxic elementsand essential elements.
Macronutrients:They are the nutrients required byplants in large amounts. They are present in plant tissues in amountsmore than 10 mmole kg–1of dry matter. Examples include hydrogen, oxygen, and nitrogen.
Micronutrients:They are also called trace elements andare present in plant bodies in very small amounts, i.e., amounts lessthan 10 mmole kg– 1of dry matter. Examples include cobalt, manganese, zinc, etc.
Beneficialnutrients: They are plant nutrientsthat may not be essential, but are beneficial to plants. Sodium,silicon, cobalt and selenium are beneficial to higher plants.
Toxicelements: Micronutrients are requiredby plants in small quantities. An excess of these nutrients mayinduce toxicity in plants. For example, when manganese is present inlarge amounts, it induces deficiencies of iron, magnesium, andcalcium by interfering with their metabolism.
Essentialelements: These elements are absolutelynecessary for plant growth and reproduction. The requirement of theseelements is specific and non-replaceable. They are further classifiedas macro and micro-nutrients.