How a stoma opens
"How a stoma opens" is a free, interactive Class 11 Biology simulation for NEET, built on the NCERT section "Epidermis and stomata" in Anatomy of Flowering Plants. Water enters two guard cells; because the inner wall facing the pore is thick and the outer wall thin, the cells bow outward and the pore opens. NEET has asked about this idea 2 times in 10 years of papers.
From the lesson Epidermis and stomata in Anatomy of Flowering Plants. Change the values and watch what happens.
What it shows
NCERT §6.1.1, Fig 6.1
Water enters two guard cells; because the inner wall facing the pore is thick and the outer wall thin, the cells bow outward and the pore opens.
Controls
3 to try
- Sliderguard-cell turgor 0–100 %
- Togglewall thickness normal / swapped (thick outer wall)
- Segmentedkidney (bean) / dumb-bell (grass) guard cells
Try this
Raise turgor until the pore is at least 6 µm wide, then swap the wall thickness and see that the same turgor no longer opens it.
Common mistake
The guard-cell wall facing the pore is thin (it is thick)
In NEET
10 years of papers
Asked 2 times in 10 years of NEET.
See the past questions: Transpiration Pull, Anatomy of Flowering Plants (chapter)
The idea behind it
NCERT §6.1.1, Figure 6.1
- In the primary body of a plant, the epidermis is the layer on the very outside. Its cells are elongated and packed tightly into one unbroken layer, which is usually a single cell thick.
- Epidermal cells are parenchyma: a large vacuole with only a thin film of cytoplasm pressed against the wall.
- A waxy, thick cuticle often covers the outer surface and cuts down water loss. Roots have no cuticle.
- Stomata are found in the epidermis of leaves and control transpiration and the exchange of gases.
- Each stoma has two guard cells around a pore. Guard cells are bean-shaped in most plants but dumb-bell shaped in grasses.
- The wall of a guard cell facing the pore (inner wall) is heavily thickened; the wall away from the pore (outer wall) is thin. Guard cells contain chloroplasts and control opening and closing.
- Epidermal cells next to the guard cells may change shape and size; these are subsidiary cells.
- Stomatal apparatus = stomatal pore + guard cells + the subsidiary cells around them.
Questions
4 answers
- What does the "How a stoma opens" simulation show?
- Water enters two guard cells; because the inner wall facing the pore is thick and the outer wall thin, the cells bow outward and the pore opens.
- What mistake does the "How a stoma opens" simulation fix?
- A common mistake it clears up: the guard-cell wall facing the pore is thin (it is thick)
- Has NEET asked about this idea?
- Yes. NEET has asked about this idea 2 times in 10 years of papers.
- Is this simulation free?
- Yes. It is free and runs in the browser on a phone or a laptop. It belongs to the lesson "Epidermis and stomata" in Anatomy of Flowering Plants (Class 11 Biology).
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