Plants, like animals, need energy to grow and function. They obtain this energy through a process called respiration. Unlike animals, however, plants produce their own food through photosynthesis. Respiration uses this food (sugars) and oxygen to generate energy. This process happens continuously, day and night.
The Process of Plant Respiration
Plant respiration is essentially the reverse of photosynthesis. During respiration:
- Plants take in oxygen from the air.
- They use this oxygen to break down sugars (produced during photosynthesis) releasing energy.
- This process releases carbon dioxide and water as byproducts.
Where does it happen? Gas exchange, crucial for respiration, occurs in various plant parts:
- Leaves: Leaves, especially those with soft, green stems, absorb oxygen directly through their surfaces. [Leaves and soft, green stems have living cells in contact with the air, and they can absorb oxygen for respiration directly through their surface].
- Stems: Woody stems have lenticels—tiny pores—that allow oxygen to reach the inner tissues. [However, the bark of woody stems is impervious to gases, so to get oxygen to the active tissue beneath, it is perforated by pores called lenticels.]
- Roots: Roots absorb oxygen from the air spaces in the soil. [The roots of a plant take up air from the spaces between the soil particles. Root hairs are in contact with the air in the soil.]
Respiration vs. Photosynthesis: Key Differences
It's important to distinguish between respiration and photosynthesis:
| Feature | Respiration | Photosynthesis |
|---|---|---|
| Time of Day | Day and night | Only during daylight |
| Process | Breaking down sugars to release energy | Making sugars using sunlight, water, and CO2 |
| Oxygen | Consumed | Produced |
| Carbon Dioxide | Produced | Consumed |
| Energy | Released | Stored in sugars |
[Plants respire all the time, whether it is dark or light. However, they only photosynthesise when they are in the light.]
Practical Implications
Understanding plant respiration is important for:
- Agriculture: Optimizing growing conditions for maximum yield.
- Environmental Science: Studying the carbon cycle and climate change. [A new study involving ANU and international collaborators has found plants release more carbon dioxide into the atmosphere than expected, highlighting the complexities of plant respiration and its role in climate change].
