Question

Which element amongst the following is required in comparatively least quantity for the growth of plant
(a) Zn
(b) N
(c) P
(d) Ca

Answer 1

Hint: The essential mineral elements can be grouped into two classes based on the amount required namely; Micronutrients and Macronutrients. Macronutrients are the minerals required in large amounts. The micronutrients are the minerals required in lesser amounts. Certain micronutrients are used in the formation of chlorophyll and some carbohydrates, conversion of starches to sugars, and its presence in plant tissue help the plant to withstand cold temperatures.

Complete answer:
The micronutrients required in lesser amounts are zinc, copper, iron, manganese, nickel, molybdenum, chlorine, and boron. Zinc forms a constituent of some enzymes. It acts as an enzyme activator. Plays a significant role in protein synthesis and redox reactions. They are absorbed from soil in ionic form. Required in all parts. The important macronutrients for plants are carbon, hydrogen, oxygen, nitrogen, Phosphorus, Sulphur, magnesium, potassium, calcium. When it is deficient, leaves become drastically reduced in size, and internodes get shortened, giving a rosette appearance. Necrosis and internal chlorosis in leaves, distorted leaf shape, reduced fruit size, suppressed seed formation, etc. are other symptoms.

Additional Information:
- The nutrient elements required by plants in very small amounts and are found in plants only in trace amounts.
- The average amount present in one gram of dry matter is usually less than 1 mg. Slight excess in the plant body can be often toxic to plants.
- Are generally involved in the functioning of enzymes by serving as co- factors or as enzyme activators.
So, the correct answer is '(a) Zn'.

Note:
- Plants do not require all the essential elements in equal amounts. Essential elements have specific structural and functional roles in the plant body.
- They form the structural framework of protoplasm and cell wall. They enter into the synthesis of several biologically important molecules such as proteins, enzymes, hormones, nucleic acids, ATP, GTP, chlorophyll, cytochromes, etc.
- They regulate the pH of the cytoplasm and vacuole sap by serving as pH buffers. They also control the permeability of cell membranes.