Correct Option
The correct option is (c) 1 and 3 only.
Explanation
Respiration in plants is a cellular process where glucose is broken down in the presence of oxygen to release energy, carbon dioxide, and water. Unlike photosynthesis, which is dependent on light, respiration is a vital metabolic process required for the survival of plant cells.
Statement-wise Analysis
- Statement 1 is Correct: The exchange of gases (oxygen and carbon dioxide) in plants primarily occurs through tiny pores located on the surface of leaves called stomata. While other parts of the plant, such as lenticels on stems and root surfaces, also participate in gas exchange, the leaves are the principal site for this activity.
- Statement 2 is Incorrect: Respiration is a continuous process that takes place 24 hours a day (both day and night) because plant cells constantly require energy for survival. Photosynthesis, on the other hand, occurs only during the day in the presence of sunlight. The misconception often arises because, at night, there is no photosynthesis to utilize the carbon dioxide produced by respiration, leading to a net release of CO2.
- Statement 3 is Correct: During the day, the rate of photosynthesis is significantly higher than the rate of respiration. Consequently, the amount of oxygen produced as a byproduct of photosynthesis far exceeds the amount of oxygen consumed by the plant for respiration. This results in a net release of oxygen into the atmosphere.
Key Takeaway
Respiration is a continuous process occurring day and night in all living cells, whereas photosynthesis is restricted to daylight hours. During the day, the net gas exchange favors oxygen release because photosynthetic output surpasses respiratory consumption.