Plants utilize which gas from the atmosphere for carrying out photosynthesis?

Introduction / Context:

Photosynthesis is one of the most fundamental processes in biology, because it is the primary way by which energy from sunlight is converted into chemical energy in plants. In this process, plants take in raw materials from their surroundings and synthesize glucose and other organic molecules. A key part of the reaction is the use of a particular gas from the atmosphere. This question checks whether the learner remembers which gas is actually consumed during photosynthesis and does not confuse it with gases produced or simply present in air.

Given Data / Assumptions:

• The process under consideration is photosynthesis in green plants.
• We are asked which gas is taken from the atmosphere during this process.
• Options are oxygen, nitrogen, carbon dioxide, hydrogen, and water vapour.
• Standard school level photosynthesis equation is assumed known.

Concept / Approach:

The simplified photosynthesis equation can be written as: 6 CO2 + 6 H2O in the presence of light and chlorophyll gives C6H12O6 + 6 O2. This expression clearly shows that carbon dioxide and water are the raw materials, while glucose and oxygen are the products. Oxygen is released into the atmosphere, not consumed from it, while nitrogen is relatively inert and not directly used in the photosynthesis reaction. Hydrogen appears as part of water, but hydrogen gas from air is not absorbed. Therefore, the correct gas taken from the atmosphere as a reactant is carbon dioxide.

Step-by-Step Solution:

Step 1: Recall the overall photosynthesis equation relating carbon dioxide, water, glucose, and oxygen. Step 2: Identify which substances are on the left side of the equation as reactants and which are on the right side as products. Step 3: Note that carbon dioxide appears as a reactant taken in from the air, and oxygen appears as a product released to the air. Step 4: Compare this understanding with the options given in the question. Step 5: Conclude that the gas utilized from the atmosphere for photosynthesis is carbon dioxide.

Verification / Alternative check:

As an alternative check, we can recall practical experiments where plants kept in closed jars with carbon dioxide absorbing chemicals show reduced photosynthesis. Another verification comes from the fact that forests are called carbon sinks, because growing plants absorb carbon dioxide. Environmental science topics like global warming also mention that plants help reduce atmospheric carbon dioxide. All these independent ideas confirm that carbon dioxide is the gas used in photosynthesis, not oxygen or nitrogen.

Why Other Options Are Wrong:

Option A, Oxygen, is incorrect because oxygen is a product of photosynthesis and is released by plants into the atmosphere. Option B, Nitrogen, is wrong because although nitrogen is abundant in air, plants mainly take up nitrogen from the soil as nitrate or ammonium, not directly as nitrogen gas for photosynthesis. Option D, Hydrogen, is not absorbed as a free gas; instead, hydrogen comes from water molecules. Option E, Water vapour, represents the gaseous form of water but is not the gas specifically mentioned as a reactant from air in the standard equation.

Common Pitfalls:

Many students confuse input and output gases and may think plants take in oxygen because humans do. Others remember that nitrogen is needed for proteins and assume it must be directly absorbed from air during photosynthesis. Another mistake is to forget that water enters mainly through roots as liquid, not as water vapour through leaves. To avoid these errors, learners should repeatedly write and interpret the photosynthesis equation and mark which substances are reactants and which are products.

Final Answer:

The gas utilized from the atmosphere during photosynthesis is Carbon dioxide.