Homeostasis in plants
| English | Chinese | Pinyin |
|---|---|---|
| stomata | 气孔 | qì kǒng |
| transpiration | 蒸腾作用 | zhēng téng zuò yòng |
| guard cell | 保卫细胞 | bǎo wèi xì bāo |
| turgid | 膨胀 | péng zhàng |
| water stress | 水分胁迫 | shuǐ fèn xié pò |
| abscisic acid | 脱落酸 | tuō luò suān |
How plants control water loss
- Stomata 气孔 are pores in a leaf.
- The plant opens and closes them to balance two needs.
- A drought hormone can shut them to save water.
Guard cells close the stomata to reduce water loss when the plant is short of water.
Closing the stomata is how a plant conserves water — part of homeostasis in plants.
A plant opens and closes its stomata to balance:
Open stomata let CO₂ in for photosynthesis but also let water escape, so the plant must balance the two.
A balancing act
- Open stomata let in carbon dioxide for photosynthesis.
- But open stomata also lose water by transpiration 蒸腾作用.
- So stomata usually open by day and close at night, on a daily rhythm.
How a stoma opens
Step through it. Guard cells pump in ions, draw in water by osmosis, swell turgid and bend apart — opening the pore.
Guard cells open a stoma by:
Taking in ions lowers their water potential; water enters, the guard cells swell turgid and bend apart.
Put the opening of a stoma in order.
Pump ions → water in by osmosis → turgid → bend apart → open. Losing the ions reverses it and the stoma closes.
How guard cells 保卫细胞 work
- Each stoma is opened and closed by two guard cells:
- to open: guard cells pump in ions → water potential falls → water enters by osmosis → they swell turgid 膨胀 and bend apart, opening the pore.
- to close: ions leave → water follows out → guard cells go floppy → the pore shuts.
Guard cells swell turgid to open the stoma, and go floppy to close it
When a plant is short of water, abscisic acid (ABA):
ABA is released under water stress and triggers stomatal closure to conserve water.
When a plant is short of water, the hormone ______ makes its stomata close.
ABA is the stress hormone that triggers stomatal closure to save water.
Inside the guard cells, the second messenger in ABA signalling is:
Calcium ions act as the second messenger that brings about stomatal closure in response to ABA.
Water stress 水分胁迫 and ABA
- When the plant is short of water (water stress), it releases the hormone abscisic acid 脱落酸 (ABA).
- ABA makes the guard cells lose ions and water, so the stomata close and save water.
- Inside the guard cells, calcium ions act as a second messenger.
You've got it
- stomata balance CO₂ in (photosynthesis) vs water loss (transpiration)
- guard cells open the pore by taking in ions + water (turgid); close it by losing them (floppy)
- under water stress, ABA makes stomata close to save water
- calcium ions act as the second messenger in the guard cells