Correct Option
The correct option is 2, 3 and 4 only.
Explanation
Gas exchange in plants differs fundamentally from animals. Plants lack specialized respiratory organs (like lungs) and a circulatory system for transporting gases. Instead, they rely on diffusion through specialized structures and the arrangement of tissues to meet their metabolic needs.
Statement-wise Analysis
- Statement 1 is Incorrect: Unlike animals, plants do not have a transport system for gases. Each plant part (root, stem, leaf) takes care of its own gas-exchange needs. There is very little transport of gases from one plant part to another.
- Statement 2 is Correct: Plant roots, stems, and leaves respire at rates far lower than animals. Consequently, their metabolic demands do not require large-scale convective transport of gases (active pumping or circulation). Simple diffusion is sufficient to meet these requirements.
- Statement 3 is Correct: The loose packing of parenchyma cells in leaves, stems, and roots creates an interconnected network of intercellular air spaces. This ensures that most cells have at least a part of their surface in contact with air, significantly reducing the distance gases must diffuse through solid tissue.
- Statement 4 is Correct: In bulky, woody stems, the interior is composed mostly of dead mechanical tissue. The living cells are organized in thin layers located just beneath the bark. These stems possess openings called lenticels, which facilitate the exchange of gases between the atmosphere and the living tissues.
Key Takeaway
Key Takeaway: Plants operate on a decentralized gas exchange system where each organ manages its own needs via diffusion. Structural adaptations like stomata, lenticels, and intercellular air spaces facilitate this process without the need for a circulatory transport system.