Question

. Classify nutrients based on their mobility. What are the common deficiency symptoms of mobile and immobile nutrients? Give examples

Answer 1

The term mobile and immobile nutrients refer to the transportability of these substances within the plant.

Classification of nutrients based on their mobility in soil and in plants are-

Mobile nutrients- the nutrients are highly soluble and these are not adsorbed on clay complexes, for example, nitrate ions, sulphate ions, chlorine ions, manganese ions .

Less mobile nutrients- they are soluble, but they are adsorbed on clay complex , so their mobility is reduced for example, ammonium ions, potassium ions, calcium ions, magnesium ions, copper ions.

Immobile nutrients- nutrient ions are highly reactive and get fixed in the soil, for example, dihydrogen phosphate ions, zinc ions.

Highly mobile nutrients are N, P and K, moderately mobile -Zn, less mobile- S, Mn, Fe, Cl, Mo and Cu , immobile- Ca and B.

If there is a deficiency of mobile nutrients, the symptoms are first seen in the older leaves, as the nutrients are transported to new growth from there. Nutrient mobiles are able to move from one part of plant to another as needed. When a nutrient shortage occurs , mobile nutrients travel to the area to solve the deficiency. For example, nitrogen accumulated in older leaves translocates to younger leaves to solve a deficiency. Nitrogen will show a deficiency on older leaves because it is a part of essential enzyme structure and has to be replaced as these enzymes are denatured and disposed .

Immobile nutrients either stay at their destination or move very little once assimilated and transported. Deficiencies of immobile nutrients first appear in the new growth as the plant was unable to take up sufficient amounts to transport them to the new shoots. Theses nutrients do not translocate to new growing areas as needed. They remain deposited in their original place in older leaves.

Symptoms caused by nutrients deficiencies are generally grouped into stunted growth, chlorosis, interveinal chlorosis, purplish-red coloring and necrosis. Nitrogen deficiency first seen on older leaves, tend to be pale green-yellow in colour, phosphorus deficiency symptoms are first seen on older foliage, are usually stunted growth and a dark green colour occurs.