Problem 78 - Objective Biology for NEET

Question

Inorganic nutrients are present in soil in the form of (a) Molecules (b) Atoms (c) Electrically charged ions (d) Parasite

Step-by-Step Solution

Answer

The inorganic nutrients are present in the soil in the form of electrically charged ions.

Step 1: Understanding the Concept

Understand that various elements and compounds exist in the soil that plants use as nutrients. These are not in complex forms such as parasites or complex molecules, but rather in simple forms that the plants can absorb.

Step 2: Analyzing the Options

Go through each of the options. Molecules and atoms are too broad categories including both organic and inorganic substances. Parasites are biotic and unrelated to inorganic nutrients.

Step 3: Selecting the Right Option

From the understanding in step 1 and the analysis in step 2, it is clear that the inorganic nutrients are present in the soil in the form of electrically charged ions. These are simple enough for the roots to absorb and utilize.

Key Concepts

Soil Composition

Soil is an essential element for plant growth, acting as both a support structure and a nutrient reservoir. It is composed of a diverse mix of components, including minerals, organic matter, air, and water. These elements are crucial for sustaining plant life.
Soil minerals such as sand, silt, and clay contribute to soil texture and fertility. Organic matter, formed from decomposed plants and animals, enriches the soil by providing nutrients and improving structure. Air and water occupy the spaces between soil particles, facilitating essential chemical reactions and nutrient transport.

• Minerals: Provide structure and store nutrients.
• Organic Matter: Enriches and stabilizes the soil.
• Air and Water: Enable nutrient movement and absorption.

The composition of soil varies greatly depending on geographic location and climatic conditions, influencing its capacity to supply nutrients to plants.

Plant Absorption

Plants absorb nutrients through their roots from the soil solution, a mixture of water and dissolved substances. Inorganic nutrients, primarily in the form of ions, are vital for plant health and development. These ions provide essential minerals necessary for various physiological processes.
Nutrient absorption involves the movement of ions from the soil into the plant root cells, often against a concentration gradient. This process typically requires energy, supplied through active transport mechanisms. The absorbed nutrients include macronutrients such as nitrogen, phosphorus, and potassium, along with micronutrients like iron, manganese, and zinc.

• Macronutrients: Required in larger amounts for fundamental roles in plant structure.
• Micronutrients: Needed in smaller quantities but are crucial for plant metabolic activities.

Effective plant absorption relies on the presence of moist soil, which enables the dissolution and mobility of nutrients, making them accessible to plant roots.

Ions in Soil

Ions are the electrically charged forms of atoms or molecules found in the soil, playing a pivotal role in plant nutrition. These can be either positive (cations) or negative (anions). The ionic form is critical because it dictates solubility, transport, and availability to plants.
Cation exchange capacity (CEC) is a key indicator of soil fertility. Soils with high CEC can store more nutrients and provide consistent access to them. Common nutrient cations include calcium (Ca²⁺), magnesium (Mg²⁺), and potassium (K⁺), while typical anions are nitrate (NO₃^-), sulfate (SO₄^2-), and phosphate (PO₄^3-).
The presence and concentration of these ions influence soil pH, affecting nutrient availability and plant growth. Understanding the dynamic nature of ions in the soil helps in managing soil fertility and optimizing plant nutrition.