Problem 77 - Objective Biology for NEET

Question

Which of the following element is not essential for plants? (a) Iron (b) Zinc (c) Potassium (d) Iodine

Step-by-Step Solution

Answer

The element which is not essential for plants among the provided options is Iodine (d).

Step 1: Identify the Essential Elements for Plants

Through studies, it has been established that there are 17 essential elements for plant growth. These elements are Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg), Sulfur (S), and Trace Elements (B, Cu, Fe, Mn, Zn, Mo, Cl).

Step 2: Compare the Given Options with the List of Essential Elements for Plants

The four elements listed in the question are Iron (Fe), Zinc (Zn), Potassium (K), and Iodine (I). Among these, Iron, Zinc, and Potassium are included in the list of essential elements for plants, while iodine is not.

Step 3: Determine the Non-Essential Element

By process of elimination, since Iron, Zinc, and Potassium are essential elements for plants and are present on the list of essential elements, Iodine, which is not on the list, is a non-essential element for plant growth.

Key Concepts

Plant Nutrition

Plants, like all living organisms, need specific nutrients to grow and thrive. These nutrients are categorized into two main groups: macro and micro-nutrients. Macro-nutrients include essential elements like Nitrogen, Phosphorus, and Potassium, which plants require in larger quantities. They play crucial roles in processes such as photosynthesis, energy transfer, and cell division.
Micro-nutrients or trace elements are needed in smaller amounts but are equally vital. These include elements like Iron, Zinc, and Manganese.

• Nitrogen (N) is critical for the formation of amino acids, the building blocks of proteins.
• Phosphorus (P) is integral to energy transfer through ATP.
• Potassium (K) participates in osmoregulation and enzyme activation.

Understanding plant nutrition helps in developing fertilization strategies and ensuring sustainable agricultural practices.

Trace Elements in Plants

Although required in minute quantities, trace elements or micro-nutrients are indispensable for plant health. They participate in various biochemical and physiological functions that are crucial for plant development.
For instance, Iron (Fe) is a key component of chlorophyll, and its absence can lead to chlorosis, a condition where leaves turn yellow due to insufficient chlorophyll.

• Zinc (Zn) is involved in the synthesis of plant hormones and enzyme functions that regulate growth.
• Boron (B) helps in cell wall formation and is critical for reproductive growth.

Ensuring an adequate supply of these elements promotes optimum plant growth and prevents deficiencies that can adversely affect crop yield and quality.

Plant Growth Requirements

For plants to grow effectively, several environmental factors and essential elements must be in balance. Plants need light, water, air, and suitable temperatures to perform photosynthesis and other physiological processes.
The primary requirements for growth include:

• Sunlight: It is the primary energy source, driving photosynthesis.
• Water: Essential for nutrient transport and photosynthesis.
• Temperature: Influences enzymatic activities and growth rates.

Macro and micro-nutrients collectively ensure that plants can build tissues and respond to environmental stresses.
Balanced fertilization and proper irrigation management are key to meeting these growth requirements, significantly impacting a plant's health and productivity.