MEANING OF PLANT NUTRIENTS
AGRICULTURAL SCIENCE

PLANT NUTRIENTS

Plants require nutrients or elements obtained from the soil for good growth and healthy development. These elements or nutrients are classified into two main groups which are:

  • Macro-Nutrients: Macro-nutrients are mineral elements or nutrients required by crops in large quantities. Examples of macro-nutrients are nitrogen, phosphorus, potassium, magnesium, calcium and sulphur.
  • Micro Nutrients or Trace Elements: Micro nutrients are mineral elements or nutrients required by crops in small quantities. Examples of micro-nutrients are zinc, copper, boron, molybdenum, iron, chlorine and manganese.

The functions and deficiency symptoms of these elements or nutrients are summarised below:

a) Nitrogen

Functions

  1. It aids plants’ growth and reproduction because it is an essential constituent of all proteins.
  2. It increases the size of grain in cereals or carbohydrate synthesis.
  3. It promotes vegetative and short system growth.
  4. Excess nitrogen delays maturation and fruiting.
  5. It promotes uptake of potassium and phosphorus from the soil.
  6. It promotes chlorophyll formation or deep green colour of leaves.
  7. It is necessary for the synthesis of plant hormones/ enzymes/ auxins.

Deficiency Symptoms

  1. Stunted growth.
  2. Yellowing of leaves (Chlorosis).
  3. Leaves tend to drop.
  4. Poor formation of fruits and flowers.

 

b) Phosphorus

Functions

  1. It aids enzyme reactions.
  2. It is a constituent of cell nucleus and essential for cell division.
  3. It increases crop resistance to diseases.
  4. It helps in ripening of fruits.
  5. It helps in root development, seed germination, fruit formation and maturity.
  6. It aids seed germination.
  7. It aids fruit formation and maturity.
  8. It improves the good taste of forages and vegetables.

Deficiency Symptoms

  1. Logging results in cereal crops.
  2. Leaves turn to purple and brownish colouration from tip backwards.
  3. Stunted growth.
  4. Inhibition of flowering, fruits and seed formation.
  5. Poor root development.
  6. Immature fruit drop.

 

c) Potassium

Functions

  1. It is an important constituent of plant tissues.
  2. It aids synthesis of carbohydrate.
  3. It activates various plant enzyme reactions.
  4. It promotes the development of young plants.
  5. It is necessary for neutralisation of organic acids in plants.
  6. It is associated with stomata movement and therefore influences water relationship within the plant.
  7. It is a major constituent of plant tissue.
  8. It helps in nitrate uptake from the soil.

Deficiency Symptoms

  1. Weak slender stems
  2. Delayed growth
  3. Premature loss of leaves
  4. Brown colour at margin of leaves.

 

d) Calcium

Functions

  1. It strengthens plant cell walls with calcium pectate.
  2. It helps in the translocation and storage of carbohydrate and proteins into seeds and tubers.
  3. It controls the toxicity of aluminium manganese and sodium ions.
  4. It is necessary for the normal growth of root tips.
  5. It strengthens plant cell walls.
  6. It helps in high flocculation i.e. good aeration, water infiltration and retention.
  7. It improves the pH of the soil so that nitrogen fixation can be carried out.

Deficiency Symptoms

  1. It causes stunting of the root system
  2. There is appearance of pale yellow colour in the leaves.
  3. Weak slender plants.

 

e) Magnesium

Functions

  1. It is important in the synthesis of carbohydrate as it is a constituent of chlorophyll.
  2. It assists in the transportation of phosphate, an essential material to developing fruit seeds.
  3. It enhances plant growth.
  4. It is required for normal cell division.
  5. It is necessary for synthesis of oils in plants.

Deficiency Symptoms

  1. Chlorosis along the leaf veins.
  2. Stunted growth.
  3. Premature leaf-fall.

 

f) Sulphur

Functions

  1. It is a constituent of plant proteins since it occurs in some amino acids such as cystine and methionine.
  2. It is also a constituent of plant hormones such as biotein and thiamine.
  3. It is essential for chlorophyll formation.
  4. It is also required for carbohydrate metabolism and nitrogen fixation by legumes.

Deficiency Symptoms

  1. Yellowing of leaves.
  2. Stunted growth.
  3. Poor rate of photosynthesis.

 

g) Iron

Functions

  1. It is necessary for chlorophyll formation.
  2. It is necessary for protein synthesis contained in chloroplasts.
  3. It is important in enzyme systems associated with oxidation and reduction reactions.

Deficiency Symptoms

  1. Chlorotic condition in leaves, which becomes pale green.

 

h) Manganese

Functions

  1. It is a constituent of enzymes which are responsible for protein synthesis.
  2. It is important for certain nitrogen transformation in plants and microorganisms.

Deficiency Symptoms

  1. Young leaves shows pale greenish yellow discolouration between veins.

 

i) Copper

Functions

  1. It is a constituent of certain enzymes
  2. It is necessary for photosynthesis.
  3. It is involved in respiration and utilization of iron.

Deficiency Symptoms

  1. Pale green colour of leaves.
  2. The tips of older leaves dry off and die.
  3. Young leaves tips die back.

 

j) Zinc

Functions

  1. It is involved in the action of certain enzymes.

Deficiency Symptoms

  1. Production of mottled or extremely small leaves.

 

k) Boron

Functions

  1. It is an important nutrient in protein synthesis.
  2. It facilitates the development of roots.
  3. It assists in the formation of fruits and seeds.
  4. It encourages the division of cells in the growing regions of plants.
  5. It increases yield.
  6. It facilitates nodulation in leguminous plants.

Deficiency Symptoms

  1. It causes the death of tips of roots and shoots.
  2. Failure of flower buds to develop.
  3. It causes poor growth of plants.
  4. It causes breaking or lodging.
  5. It decreases the rate of water absorption and translocation of sugars.

 

l) Molybdenum

Functions

  1. It aids nitrogen fixation acids and proteins.
  2. It is an essential part of enzymatic system involved in facilitating nitrogen change, breakdown of leaf edges.

Deficiency Symptoms

  1. Promotes metabolism of nitrates into amino acids and proteins.
  2. It causes mottled leaves.
  3. It leads to curling.
  4. It causes premature flower drops.

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