14.2 Vascular Plant Systems

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14.2 Vascular Plant Systems

• Shoot System

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• The shoot system includes stems, leaves, and
  flowers.
• Some stems are flexible and slender. These are
  called
• herbaceous (hur BAY shuhs) stems.
• Other stems, such as those of trees, are large
  and woody.

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Stem Functions

• Stems support the plant.
• Stems hold the leaves up toward the light.
• Inside a stem, water and minerals move through
  the xylem and sugars move through the phloem.
• Stems of some plants also store water or starch.
• Green stems make glucose through photosynthesis.

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Woody Stems

• A woody stem is hard, strong, and rigid.
• Most plants with woody stems are dicot trees and
  shrubs that live for many years
• Each year's growth has dark and light bands of
  xylem cells.

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• During wet weather, large xylem cells are
  produced.
• In the dry summer, the xylem cells are small and
  close together.

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Stem Adaptations

• Plant stems have many unusual adaptations.
• Cacti have green succulent stems that store
  water.
• The stored water is used to make glucose for the
  plant.
• Tendrils on grape plants are modified stems that
  help them climb.

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Leaf Functions

• Each leaf is a specialized organ with three main
  functions.
• Leaves capture light from the sun.
• Leaves make glucose through photosynthesis.
• Leaves exchange gases with the environment.

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Leaf Structure

• A leaf is made of layers.
• The surface layers are the waxy cuticle and the
  epidermis.
• Inside is the moist mesophyll (MEHZ oh FIHL)
  layer, where photosynthesis occurs.
• Gases are exchanged with the environment through
  stomates in the plant's surface.

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Leaf Adaptations

• The shapes and sizes of leaves vary, depending on
  their environment.
• Plants in shady forests have large leaves to
  capture light.
• Plants in dry environments have small, thick,
  wax-coated leaves to prevent
• drying.

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End