Exchange and transport in plants：練習問題

• a.Palisade mesophyll
• b.Xylem tissue
• c.Spongy mesophyll
• d.Epidermal tissue

• a.

  Diffusion of carbon dioxide into the spongy mesophyll; increased by closing the stomata during a drought.

• b.

  Movement of water from roots through the xylem and out of the stomata; increased by hot, dry, and windy conditions.

• c.

  Movement of water from leaves to the roots via the phloem; increased by cold and calm conditions.

• d.

  Movement of dissolved sugars through the phloem to the roots; increased by high humidity and low temperatures.

• a.

  Phloem is reinforced with lignin to support the plant against gravity

• b.

  Xylem is made of hollow, dead cells to facilitate the transpiration stream of water and minerals

• c.

  Phloem is made of dead cells to transport dissolved sugars via translocation

• d.

  Xylem contains sieve plates to allow for the movement of glucose to the roots

• a.The rate of translocation will increase; this is controlled by phloem cells.
• b.The stomata will close; this is controlled by the guard cells.
• c.The stomata will open wider; this is controlled by epidermal cells.
• d.The xylem will narrow; this is controlled by the mesophyll cells.

• a.The stomata open wider to increase the rate of photosynthesis, accelerating the flow of sugars in the xylem.
• b.The stomata close to trap oxygen, which increases the rate of mineral ion absorption by the roots.
• c.The guard cells become turgid to close the stomata, forcing water to move through the phloem instead.
• d.The stomata close to prevent wilting, which reduces the upward movement of water through the xylem.

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