Correct Option
The correct option is (c) 2 and 3 only.
Explanation
The balance of atmospheric gases is maintained through biogeochemical cycles, specifically the oxygen and carbon cycles. In plants, two opposing metabolic processes-photosynthesis and respiration-determine the net exchange of gases with the atmosphere.
Statement-wise Analysis
- Statement 1 is Incorrect: During photosynthesis, plants absorb carbon dioxide ($CO_2$) and water ($H_2O$) in the presence of sunlight to synthesize glucose. The byproduct released during this process is oxygen ($O_2$), not carbon dioxide.
- Statement 2 is Correct: Like all living organisms, plants perform cellular respiration to generate energy for survival. In this process, they consume oxygen ($O_2$) to break down glucose, releasing carbon dioxide ($CO_2$) and water. This process occurs continuously, both day and night.
- Statement 3 is Correct: While plants consume oxygen for respiration, the rate of photosynthesis during daylight hours is significantly higher than the rate of respiration. Consequently, the total volume of oxygen produced by plants far exceeds the volume consumed, resulting in a net release of oxygen into the atmosphere.
Key Takeaway: Plants act as net producers of oxygen because the oxygen generated during photosynthesis surpasses the oxygen consumed during respiration over a complete daily cycle.