During night, the plants release major proportion of carbon dioxide.

Explanation

**Step-by-Step Solution:**

1. **Understanding Plant Processes**: During the day, plants undergo two main processes: photosynthesis and respiration. Photosynthesis occurs in the presence of sunlight, where plants convert carbon dioxide and water into glucose and oxygen using sunlight.

2. **Photosynthesis vs. Respiration**: During the day, while photosynthesis is taking place, plants also respire. In respiration, plants take in oxygen and release carbon dioxide. However, the amount of oxygen released during photosynthesis is greater than the carbon dioxide produced during respiration, resulting in a net release of oxygen during the day.

3. **Nighttime Processes**: At night, there is no sunlight, so photosynthesis cannot occur. However, plants continue to respire, which means they take in oxygen and release carbon dioxide. Since photosynthesis is not happening at night, the carbon dioxide released during respiration is not offset by any oxygen production.

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