3.1 - Main Inorganic Nutrients

Like all living organisms, plants also require enough and complete nutrients in life. Inorganic nutrients are needed by plants to produce organic compounds such as carbohydrates and proteins.

Macronutrients and Micronutrients Required by Plants

Inorganic nutrients needed by plants can be divided into 2 types.

Macronutrients

• Carbon (C)
• Calcium (Ca)
• Hydrogen (H)
• Magnesium (Mg)
• Oxygen (O)
• Phosphorus (P)
• Nitrogen (N)
• Sulphur (S)
• Potassium (K)

Micronutrients

• Chlorine (Cl)
• Zinc (Zn)
• Iron (Fe)
• Copper (Cu)
• Manganese (Mn)
• Nickel (Ni)
• Boron (B)
• Molybdenum (Mo)

Carbon, hydrogen and oxygen are main macronutrients that can be easily obtained from the outer environment of plants. These macronutrients form most of the dry mass of plants. Other nutrients can be acquired from the soil in the form of mineral salts.

The Necessity of Macronutrients in Plants

Every macronutrient and micronutrient have their respective functions for optimum growth and development of the plants. The absence of one or more nutrients can affect the health and growth of the plants.

Macronutrients and Micronutrients, Functions and Effects of deficiency

Macronutrients

Carbon, Oxygen and Hydrogen

• Functions:
  • Most important components in carbon and oxygen cycle
  • Components found in all organic compounds of plants
  • Major components in glucose synthesis
• Effects of deficiency:
  • Photosynthesis process cannot be carried out
  • Oxygen produced is lesser
  • Growth ceased and cause death due to absence of glucose

Nitrogen

• Functions:
  • Required for the formation of chlorophyll which gives the green color of the plants
  • The main component in proteins, nucleic acids and enzymes in photosynthesis and respiration process
• Effects of deficiency:
  • Chlorosis (yellowing of the leaves), especially on matured leaves
  • Underlying leaves fall off
  • Process of protein synthesis affected
  • Stunted growth

Potassium

• Functions:
  • Needed for the synthesis of protein and metabolism of carbohydrates
  • Cofactor of some of the enzymes
  • Maintain the turgidity of the plants
• Effects of deficiency:
  • Affect the synthesis of protein
  • Yellowing of the edges of the leaves
  • Premature death

Calcium

• Functions:
  • Main component of middle lamella, cell wall and spindle fibres
• Effects of deficiency:
  • Cease growth
  • Leaves distorted and lobed
  • Yellowing between leaf veins

Magnesium

• Functions:
  • Needed to build the structure of chlorophyll molecule
  • Activate enzyme activities
  • Help in carbohydrate metabolism
• Effects of deficiency:
  • Yellowing between leaf veins
  • Red spots on the suface of leaves
  • Lobed leaves

Phosphorus

• Functions:
  • Required for the synthesis of nucleic acids, ATP and phospholipids
  • Act as coenzyme in photosynthesis and respiration process
• Effects of deficiency:
  • Unhealthy root growth
  • Leaves turn dark green and dull in color
  • Red or purple spots on older leaves

Sulphur

• Functions:
  • Component in some of the amino acids
  • Component of vitamin B and a few types of enzymes
• Effects of deficiency:
  • Yellowing of the leaves or the whole plants

Micronutrients

Chlorine

• Functions:
  • Maintain the osmotic balance of cells
  • Important in photosynthesis reaction
• Effects of deficiency:
  • Plants wilt
  • Growth slows down
  • Chlorosis of the leaves
  • Less fruits produced

Iron

• Functions:
  • Cofactor in the synthesis of chlorophyll
  • Needed for the growth of young plants
• Effects of deficiency:
  • Yellowing of young leaves

Manganese

• Functions:
  • Activate enzymes in photosynthesis
  • Needed for cell respiration and nitrogen metabolism
• Effects of deficiency:
  • Network of dark green leaf veins with background of light green
  • Light brown or grey spots between leaf veins

Boron

• Functions:
  • Helps calcium ion absorption from the roots and translocation of sucrose
  • Carbohydrate metabolism and facilitates seeds germination
• Effects of deficiency:
  • Death of terminal buds
  • Abnormal growth
  • Thickening of leaves, rolled up and fragile

Zinc

• Functions:
  • Forms leaves
  • Growth hormone synthesis such as auxin
  • Cofactor in carbohydrate metabolism
• Effects of deficiency:
  • Spots formed on the surface of the leaves with chlorosis parts
  • Stunted growth

Copper

• Functions:
  • Required for the metabolism of nitrogen and photosynthesis
  • Important for growth, reproduction and formation of flowers
• Effects of deficiency:
  • Death of young apex shoots
  • Brown spots on terminal leaves
  • Stunted growth

Nickel

• Functions:
  • Component of enzymes involved in the decomposition of urea to ammonia
• Effects of deficiency:
  • Stunted growth
  • Crop production reduces
  • Accumulation of urea causes burnt marks at the end of the leaves

Molybdenum

• Functions:
  • Fixation of nitrogen and nitrate reduction during protein synthesis
• Effects of deficiency:
  • Chlorosis happens between matured leaf veins
  • Leaves turn dark green
  • Crop production reduces

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Knop's solution consists of all the nutrients required by the plants to grow and maintain health. The composition of Knop's solution includes the following.

• 0.8 g calcium nitrate, Ca(NO3)2
• 0.2 g potassium nitrate, KNO3
• 0.2 g potassium dihydrogen phosphate, KH2PO4
• 0.2 g magnesium sulphate, MgSO4
• Traces of iron (III) phosphate, FePO4
• 1000 ml distilled water