Question

Exanthema is result of deficiency of
A. Cu
B. Ca
C. P
D. Na

Answer 1

Exanthema is caused due to the deficiency of micronutrient. This micronutrient helps in metabolism and growth of plants.

Complete answer:
There are several elements required by the plants. These elements are needed for the proper growth and to complete the life cycle of the plants. Depending upon the amount of quantity or concentration required by the plants, they are divided into macronutrients and micronutrients. Micronutrients are the elements which require less concentration or in less amount or quantity. However, the macronutrients are required in larger amounts or quantities as compared to micronutrients. All these elements perform several functions in plants such as help in metabolic processes, helps in maintaining the osmotic concentration, buffering action, electron transport system, etc.
Some of the common examples of micronutrients and macronutrients:
Micronutrients: Iron (Fe), chlorine (Cl), copper (Cu), zinc (Zn), molybdenum (Mo)
Macronutrients: potassium (K), phosphorus (P), calcium (Ca), sulphur (S), magnesium (Mg), sodium (Na)
Whenever the amount of micronutrients increases or decreases, it leads to the toxicity or deficiency in plants respectively. When the plants are deficient in some micronutrient it starts showing some morphological changes. These changes are different depending upon which element is deficient in the plant. Some of the deficiency symptoms included premature leaves may fall off, chlorosis, exanthema, stunted plant growth, necrosis, etc.
Therefore the exanthema is the result of deficiency of micronutrients. It can also be caused by the soil factors such as increasing in pH, salinity, drainage which leads to unavailability of the copper for the plants. The major symptoms of exanthema are decreased fruit-bearing capacity, dying and falling of leaves, high yield of gum from the bark of the trees.

Hence the correct answer is option A that is copper (Cu). All other elements in the options are macronutrients.

Note: Plants take copper from the soil. It is absorbed in the form of the cupric ions. Copper is essential for the plants because it helps in the allover metabolic activity, growth, formation of lignin in the cell wall. It is associated with the enzymes involved in the redox reaction.