12 MINERAL NUTRITION

MINERAL NUTRITION practice questions

Mineral Nutrition

Carbohydrates, proteins, lipids, water, and minerals are required for all living creatures to survive. Plants, too, require nutrients for growth and development.

Essential Mineral Elements

Mineral needs vary depending on the plant. There is a criterion for determining whether or not an ingredient is necessary.

It contains the following items:

  • The element must be required for proper development and reproduction. If such a component is missing, the Plants won’t be able to finish their life cycle.
  • The element’s need must be precise, and no other element should be able to substitute it.
  • The element must play a direct role in plant metabolism.

Functions of Mineral Nutrients:

  • Carbon, hydrogen and oxygen enter into the cell wall and protoplasm and form the plant body.
  • The minerals present in the cell sap maintain the osmotic pressure of the cell.
  • Calcium, sodium and potassium maintain the permeability of cell membrane.
  • The cations and anions affect the pH of the cell sap.
  • A few salts and minerals balance the harmful effect of other nutrients.
  • Several elements act as catalyst for biochemical reactions.

Macronutrients

These nutrients are required by the plants in large quantities. These include carbon, hydrogen, nitrogen, oxygen, phosphorus, Sulphur, potassium, etc.

Micronutrients

These nutrients are required by the plants in small quantities. These include iron, copper, manganese, molybdenum, chlorine, etc.

Role of Macro and Micronutrients

Mineral Nutrients

Functions

Nitrogen Important constituent of nucleic acid, protein, hormones and vitamins.
Phosphorus Promotes root growth and fruit ripening.
Potassium It acts as an activator for several enzymes.
Calcium Facilitates the formation of middle lamella of plants and acts as an enzyme activator.
Magnesium Plays a vital role in the metabolism of carbohydrates, lipids.
Sulphur Major constituent of amino acids and vitamins.
Iron Plays an important role in the energy conversion reaction reactions of respiration and photosynthesis, activates nitrate reductase and aconitase.
Manganese Essential for chlorophyll synthesis, initiate photolysis of water.
Copper Plays an important role in photophosphorylation.
Molybdenum It helps in the synthesis of ascorbic acid.
Chlorine Helps in the photolysis of water in photosystem-II.

 

Deficiency of Mineral Nutrients

 

Mineral Nutrients

Deficiency Symptoms

Nitrogen Impaired plant growth, chlorosis, delayed flowering, and fruiting.
Phosphorus Premature leaf fall, necrosis.
Sulphur Delayed flowering and fruiting, premature leaf fall.
Potassium Mottled chlorosis, inhibition of protein synthesis and photosynthesis.
Calcium Chlorosis, distortion of leaf shape.
Magnesium Interveinal chlorosis, depression of internal phloem.
Iron Chlorosis, inhibition of protein synthesis and chloroplast formation.
Chlorine Wilting of leaves, brown edges, leaf spots.
Copper Causes “die back” disease in leaves, Reduction in vegetative and reproductive growth.

 

Autotroph

An organism that synthesize its required nutrients from simple and inorganic substance; Example: plants, blue green algae (cyanobacteria)

Heterotroph

An organism that cannot synthesise its own nutrients and depend on others. Example: Bacteria, protists, members of animalia.

Biological nitrogen fixation

Conversion of atmospheric nitrogen into organic compounds by living organisms.

Chlorosis

Yellowing of leaves due to loss of chlorophyll.

Nitrification and Denitrification

Conversion of ammonia (NH3) into nitrite and then to nitrate. A process of conversion of nitrate into nitrous oxide and nitrogen gas (N2).

Leg Hemoglobin

Pinkish pigment found in the root nodules of legumes. It acts as oxygen scavenger and protects the nitrogenase enzyme from oxidation.

Flux

The movement of ions is called flux. Influx is inward movement of ions into the cells and efflux is the outward movement of ions.

Inhibition of cell division: Deficiency of N, K, S. and Mo.

Necrosis

Death of tissues particularly leaf tissue due to deficiency of Ca, Mg, Cu, K.

Delayed Flowering: due to deficiency of N, S, Mo.

Mineral Nutrition

Plants require mineral elements for their growth and development. The utilization of various absorbed ions by a plant for growth and development is called mineral nutrition of the plant.

Hydroponics

Soil-less culture of plants, where roots are immersed in nutrient solution (without soil) is called hydroponics. The result obtained from hydroponics may be used to determine deficiency symptoms of essential elements.

Active Transport

Absorption occurring at the expense of metabolic energy.

Passive Transport

Absorption of minerals with concentration gradient by the process of diffusion without the expense of metabolic energy.

Nitrogen Cycle

Nitrogen Fixation:

The process of conversion of nitrogen to ammonia is called nitrogen fixation. In nature lightening and ultraviolet radiation provide energy to convert atmospheric nitrogen into nitrogen oxide ( No, NO2 and N2O).

Ammonification:

The decomposition of organic nitrogen of dead plants and animals into ammonia is called ammonification.

Nitrification:

Ammonia is first oxidized to nitrite by bacteria Nitrosomonas or Nitrococcus which is further oxidized to nitrate with help of bacteria Nitrobactor. These processes are called nitrification.

Denitrification:

Nitrates formed is absorbed by plants and transported to leaves. Nitrates is converted into free nitrogen by the process called denitrificaion by bacteria Pseudomonas and Thiobacillus.

Biological Nitrogen Fixation:

Reduction of nitrogen to ammonia by living organism is called Biological Nitrogen Fixation. The enzyme nitrogenase is present in prokaryotic organism called nitrogen fixer.

Role of microbes in nitrogen cycle

  • Rhizobium, Azotobacter, Rhodospirillum; Fix atmospheric nitrogen
  • Nitrosomonas and/ or Nitrococcus: Conversion of ammonia to nitrite
  • Nitrobacter: Conversion of nitrite into nitrate.
  • Pseudomonas and Thiobacillus: reduce nitrate into nitrogen.
  • 12 MINERAL NUTRITION

Steps of nodule formation

  • Rhizobium bacteria present in soil contact a susceptible root hair.
  • Infection of the root hair cause it to curve and deformed due to chemical secretion.
  • An infection thread is produced carrying the bacteria into the cortex of the root.
  • The bacteria get modified into rod-shaped bacteria and cause inner cortical and pericycle cells to divide plant produce cytokinin and auxin to stimulate cell division and enlarge to form nodules.
  • Division and growth of cortical and pericycle cells lead to nodule formation.

Mechanisms of N2 fixation

It requires 3 components:

  • A strong reducing agent like FADH2, NADPH2.
  • Nitrogenase enzyme.
  • ATP (as energy service).

Steps:

  • Formation of Diamide.
  • Formation of Hydrazine (N2H4).
  • Formation of Ammonia.
  • PRACTICE QUESTION

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