The correct option is 1 only
Explanation
Gaseous exchange in plants involves two primary physiological processes: respiration and photosynthesis. Respiration occurs continuously (day and night), involving the intake of oxygen and release of carbon dioxide. Photosynthesis occurs only in the presence of sunlight, involving the intake of carbon dioxide and release of oxygen. The net gaseous exchange depends on the relative rates of these two processes at different times.
Statement-wise Analysis
- Statement 1 is Correct: At night, photosynthesis ceases due to the absence of sunlight. However, cellular respiration continues to sustain metabolic activities. During this time, plants consume oxygen and release carbon dioxide. Since there is no photosynthesis to utilize the carbon dioxide produced, the elimination of carbon dioxide is the predominant gaseous exchange event.
- Statement 2 is Incorrect: During the day, both respiration and photosynthesis occur simultaneously. However, the rate of photosynthesis is typically much higher than the rate of respiration. The carbon dioxide generated during respiration is internally utilized for photosynthesis, and additional carbon dioxide is absorbed from the atmosphere. Consequently, the release of oxygen (a byproduct of photosynthesis) is the major event, not the release of carbon dioxide.
Key Takeaway
Net Gaseous Exchange Rule: During the day, photosynthesis dominates, resulting in a net release of oxygen. At night, only respiration occurs, resulting in a net release of carbon dioxide.