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CIE A Level Biology復(fù)習(xí)筆記14.2.1 Stomata

Category: A-level課程, 教材筆記, 福利干貨 Date: 2022年8月11日上午10:04

Stomata

Plants carry out?homeostasis?– just like animals they need to maintain a?constant internal environment
- For example, mesophyll cells in leaves require a?constant supply of carbon dioxide?for?photosynthesis
Stomata?(specifically the?guard cells) control the diffusion of gases in and out of leaves
- This means stomata?control the entry of carbon dioxide?into leaves

Response of guard cells & stomata table

Stomata-table-1

Regulation of stomatal aperture balances the need for carbon dioxide uptake by diffusion with the need to minimise water loss by transpiration

Advantages & disadvantages of stomatal opening & closure table

Stomata-table-2

Exam Tip

A stoma is actually the aperture (hole) between two guard cells, but the term is often used to refer to the whole unit (the two guard cells and the hole between them).Don’t forget – stoma (singular) refers to one of these units, whereas stomata (plural) refers to many!

Opening & Closing of Stomata

Stomata?open?and?close?in a?daily rhythm
- Even when the plant is kept in?constant light?or?constant darkness, the daily rhythm of opening and closing of the stomata continues
Opening of stomata?during the day:
- maintains the?inward diffusion of carbon dioxide?and the?outward diffusion of oxygen
- allows the?outward diffusion of water?vapour?in transpiration
Closing of stomata?at night?when photosynthesis cannot occur:
- reduces?the rate of?transpiration
- conserves water