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Plant Structure

  • Roots anchor the plant to the ground. They are also the site of absorption of water and minerals from the soil and a site of food storage.
  • The leaf is the primary site of photosynthesis in most plants. The outer layer of the leaf is covered with a cuticle to prevent the loss of water. The cells of the mesophyll contain numerous chloroplasts where photosynthesis takes place.
  • Stomata are pores on the surface of leaves that allow for gas exchange. Guard cells flanking a stoma change shape in order to control the opening and closing of the stoma.
  • The xylem conducts water and minerals from the roots to the rest of the plant. The xylem is composed of tracheids and vessel elements arranged in chains.
  • The phloem conducts nutrients from sites of production to the rest of the plant. Companion cells associated with the sieve-tube elements regulate the flow of nutrients.
  • Plants can grow indefinitely due to the undifferentiated, embryonic cells in their meristems. Primary growth increases the length of the plant. Non-herbaceous plants also undergo secondary growth, which results in an increase in width.

Plant Structure

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AP Biology Intro