Transpiration · ⁨蒸腾作用⁩

The price of open pores

• To let carbon dioxide in, a leaf must open its stomata 气孔 — but water vapour escapes at the same time.
• This loss of water is transpiration 蒸腾作用.

What transpiration is

• Transpiration is the loss of water vapour from a plant's leaves, mainly through the stomata.
• It pulls the transpiration stream of water up from the roots.

Factors affecting the rate

• Transpiration speeds up with more light, higher temperature, more wind, and lower humidity 湿度.
• Each makes evaporation from the leaf faster.

Each environmental factor that speeds up evaporation raises the transpiration rate.

Wilting and control

• If a plant loses water faster than it takes it up, cells become flaccid and it wilts.
• Guard cells 保卫细胞 can close the stomata to reduce water loss.

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