Gaseous Exchange in Plants and Stomata

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Questions and Answers

Plants require ______ gases to perform cellular respiration.

oxygen

The exchange of oxygen and carbon dioxide occurs through ______.

stomata

Each ______ is guarded by a pair of guard cells.

stoma

The condition of guard cells depends on potassium ion ______ by the cells.

<p>uptake</p> Signup and view all the answers

During daytime, photosynthesis in guard cells produces dissolved sugar called ______.

<p>sucrose</p> Signup and view all the answers

The ______ of the guard cells increases when potassium ions enter them.

<p>solute potential</p> Signup and view all the answers

In the absence of light, sugar in guard cells converts into ______.

<p>starch</p> Signup and view all the answers

The potassium ions ______ from the guard cells to close the stoma.

<p>move out</p> Signup and view all the answers

Flashcards

Stomata

Tiny pores on the lower leaf surface, responsible for gas exchange in plants.

Guard Cells

Specialized cells flanking each stoma, controlling its opening and closing.

Gaseous Exchange in Plants

The process of taking in carbon dioxide (CO2) and releasing oxygen (O2) by plants for photosynthesis.

Turgor Pressure in Guard Cells

The change in water potential within guard cells due to potassium ion uptake or release, causing them to swell (turgid) or shrink (flaccid).

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Stomatal Opening

Potassium ions (K+) move into guard cells, increasing their solute potential (making them saltier) and drawing water in through osmosis, causing them to swell and open the stoma.

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Stomatal Closing

Potassium ions (K+) move out of guard cells, decreasing their solute potential and causing water to leave through osmosis, making them shrink and close the stoma.

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Sugar Concentration and Stomata

The concentration of sugars (sucrose) in guard cells increases during the day due to photosynthesis, making the cells take in water and open the stomata. At night, sugars convert to starch, causing water loss and stomatal closure.

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Oxygen Requirement in Plants

Plants need oxygen for cellular respiration, just like animals, to release energy from food.

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Study Notes

Gaseous Exchange in Plants

  • Plants require oxygen for cellular respiration, like other organisms.
  • Unlike animals, plants synthesize their own food through photosynthesis.
  • Photosynthesis requires efficient gas exchange, including absorption of light.
  • Gas exchange occurs through stomata.

Stomata

  • Stomata are pores on the lower epidermis of leaves.
  • Each stoma is controlled by a pair of guard cells that change shape to open or close the pore.
  • Guard cells have chloroplasts for photosynthesis.
  • Stomatal opening and closing depends on guard cell turgidity.
  • Factors influencing turgidity include potassium ion (K+) uptake and sucrose concentration.

Stomatal Opening

  • Potassium ions enter guard cells, increasing solute potential and lowering water potential.
  • Water moves into guard cells via osmosis, making them turgid.
  • Guard cell shape changes, curving outwards, opening the stoma.
  • High sucrose concentration in guard cells during the day (photosynthesis) lowers water potential, drawing water to stomata and opening them.

Stomatal Closing

  • Potassium ions leave guard cells, reducing solute potential and increasing water potential.
  • Water moves out of guard cells via osmosis, making them flaccid.
  • Guard cells revert to their original shape, closing the stoma.
  • Low sucrose concentration in guard cells at night (no photosynthesis) increases water potential, causing water to leave guard cells and closing the stoma.

Water Deficiency

  • Water deficiency in plants causes guard cells to become flaccid, closing stomata to conserve water.
  • Sufficient water causes guard cells to become turgid, opening stomata for gas exchange.

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