Biology · Respiration in Plants · NEET
NCERT gives three clear reasons. First, each plant part looks after its own gas needs; there is very little transport of gases from one part to another. Second, plants have low gas demands, because roots, stems and leaves respire far more slowly than animals do. Third, the distance a gas must diffuse is small, since almost every living cell has part of its surface in contact with air. So simple diffusion is enough and no pump or lung is needed. This point is a favourite NEET reasoning question.
Both are pores for gas exchange, but they sit in different places. Stomata are tiny pores in the epidermis of leaves and young green stems, bordered by two guard cells. Lenticels are lens-shaped openings in the bark (periderm) of woody stems and roots, loosely filled with complementary cells. Stomata can open and close; lenticels stay permanently open. Remember: leaf and green tissue use stomata, woody tissue uses lenticels.
In woody stems the living cells are arranged in thin layers just inside and beneath the bark, and these connect to the air through lenticels. The cells in the deep interior are dead and only give mechanical support, so they do not need oxygen. Loosely packed parenchyma also creates a connected network of air spaces. This is why even a large tree does not need a transport system for gases.
No. Gaseous exchange here is passive diffusion, driven only by concentration differences. O2 moves in where it is being used up and CO2 moves out where it is being produced. No ATP is spent on this movement. Do not confuse this with active transport. NEET may trap you by calling the exchange an active or energy-requiring process.
No. Breathing in animals uses special organs (lungs, gills) and muscular movements. Plants have no such organs and no breathing movements. They simply exchange gases by diffusion through stomata and lenticels. So the correct term for plants is gaseous exchange, not breathing.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Lenticels are lens-shaped openings in the bark (periderm) of woody stems and roots. They are loosely filled with complementary cells and permit gaseous exchange between the inner living tissues and the atmosphere by diffusion.
Stomata are pores in the epidermis of leaves and green stems that allow O2 to diffuse in and CO2 to diffuse out. They are bordered by guard cells and can open and close, unlike the permanently open lenticels.
Because plants have no respiratory organs or breathing movements. Gases simply move down their concentration gradients through stomata and lenticels without any energy being spent, which is exactly the definition of diffusion.
Yes. Almost every living cell in a plant has at least part of its surface exposed to air, helped by loosely packed parenchyma and air spaces. Deep interior cells of woody stems are dead, so they do not need oxygen.
