Essential Nutrients of Plants
* Nutrition is the process of absorption of various minerals ions for growth.
* The elements essential for plant growth are further divided into macronutrients and micronutrients.
* The elements that are required by a plant in large amounts are called macronutrients.
* The elements that are required in minute quantities are called micronutrients or trace elements.
Macronutrients of Plants
* Elements that are required by plants in large amounts are called macronutrients.
* Elements like carbon, hydrogen, oxygen, nitrogen, phosphorus, sulphur, potassium, calcium and magnesium are micronutrients.
* The concentration of essential elements below which plant growth is retarded is termed as critical concentration.
* The deficiency of different elements causes different symptoms in a plant.
Micronutrients of Plants
* The elements that are required in minute quantities by plants such as iron, manganese, copper, molybdenum, zinc, boron, chlorine and nickel are called micronutrients or trace elements.
* Micronutrients occur as the constituents of several enzymes that catalyze biological reactions.
* Any mineral ion concentration in tissues that reduces their dry weight by about 10 percent is considered toxic.
* The excess concentration of an element, affects the uptake of another element.
Mechanism of Absorption of Elements
* The two main phases of absorption are passive absorption and active absorption.
* Passive absorption is a fast process whereas active absorption is a slow process.
* Active absorption involves the spending of energy.
* The movement of ions is called flux.
* Inward movement into the cells is called influx and outward movement is called efflux.
Nitrogen Cycle
* The conversion of elemental nitrogen to ammonia by soil bacteria is called nitrogen fixation.
* Nitrogen present in plants reaches animals through the food they eat.
* The nitrogen content of dead plants and animals is decomposed by ammonifying bacteria to form ammonia. This process is called ammonification.
* The process of conversion of ammonia to nitrites and nitrates is called nitrification.
* The process of conversion of nitrates to nitrogen by denitrifying bacteria is called denitrification.
Biological Nitrogen Fixation
* The process by which living organisms fix atmospheric nitrogen by converting it to ammonia is called biological nitrogen fixation.
* Nitrogen fixing microbes have a special enzyme called nitrogenise, which reduce nitrogen to ammonia.
* Rhizobium in the soil multiply around the roots and get attached to root hair cells and develop into nodules.
* The formation of each molecule of ammonia requires 8 molecules of ATP.
* Amino acid synthesis in plants takes place in two ways: reductive amination and transamination.