Question

The 17$^{th}$ essential micronutrient recently identified for the plant growth and development is}

• A. Vanadium
• B. Cobalt
• C. Nickel
• D. Silicon

Hint:

Nickel (Ni) is the 17th essential plant nutrient. Its primary metabolic role is as a cofactor for the enzyme urease, which prevents toxic urea accumulation in leaf tissues.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
For an element to be classified as an essential plant nutrient, it must meet Arnon and Stout's criteria of essentiality.
These criteria state that the plant cannot complete its life cycle without the element, the element's function cannot be replaced by any other element, and the element must be directly involved in plant metabolism.
Currently, there are 17 recognized essential elements required for plant growth and development.

Step 2: Detailed Explanation:
For many years, only 16 elements were classified as essential for higher plants.
In the late 1980s, research demonstrated that nickel (Ni) is required for the activation of the enzyme urease.
Urease catalyzes the hydrolysis of urea into ammonia and carbon dioxide:
\[ \text{Urea} + H_2O \xrightarrow{\text{Urease}} 2NH_3 + CO_2 \]
Without nickel, urea accumulates in plant tissues, leading to toxic necrosis of the leaf tips.
Following this discovery, the Association of American Plant Food Control Officials (AAPFCO) and plant physiologists officially recognized nickel as the 17th essential plant nutrient in 2004.
Other elements like cobalt, silicon, and vanadium are beneficial for certain plant species but do not meet the strict criteria of essentiality for all higher plants.
Therefore, nickel is the 17th essential micronutrient.

Step 3: Final Answer
The 17th essential micronutrient identified for plant growth is nickel.