13.3 Nonflowering Vascular Plants

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13.3 Nonflowering Vascular Plants

• Gymnosperms

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• Nonflowering vascular plants that produce seeds
  are called gymnosperms.

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• Conebearing trees, such as pine and redwood, are
  the most common gymnosperms alive today.

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• Because of their seeds and other adaptations,
  these plants live and reproduce in places where
  ferns, horsetails, and club
• mosses cannot.

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• A seed is an adaptation for protecting and
  nourishing a plant embryo.

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• The embryo inside a seed may remain dormant for a
  long period of time. Then, when the conditions
  are right, it can begin growing.

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• Sperm cells develop inside protective cases that
  can be carried by moving air. (Pollen)

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• As a result, gymnosperms grow in deserts and on
  dry, windy mountaintops.

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• There are four main groups of gymnosperms alive
  today.

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• The most common living gymnosperms, the conifers,
  have needle-shaped leaves and seeds produced in
  cones.

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• Cycads (SY kadz) are relics of the ancient
  forests.

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• This gnetophytes (NEE toh FYTS) has long
  straplike leaves and bears clusters of small
  cones on short stalks.

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• The ginkgo, also called the maidenhair tree, has
  fan-shaped leaves and fleshy seeds. Unlike other
  gymnosperms, the leaves of a ginkgo fall from the
  tree in autumn.

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Life Cycle of Gymnosperms

• Example Pine Tree

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• The life cycles of gymnosperms differ greatly
  from the life cycles of ferns, horsetails, and
  club mosses.

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• The pine tree is the sporophyte generation. It
  has two types of cones.

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• The large woody cones produce spores that develop
  into female gametophytes.

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• Smaller, nonwoody cones produce spores that
  develop into male gametophytes.

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• The female gametophyte remains in the cone. It
  grows into a many-celled mass in which several
  egg cells begin to develop.

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• The male gametophyte is packaged into a tiny
  pollen grain. These are released and carried by
  the wind.

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• When the wind-borne pollen reaches a cone where
  the female gametophyte is developing, pollination
  occurs.

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• The male gametophyte grows a pollen tube through
  which sperm can reach the egg cell. Fertilization
  occurs as the sperm and egg fuse. The fertilized
  egg then develops into an embryo.

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• The embryo is packaged into a seed, along with a
  food supply.

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• When the seed sprouts and grows into a young
  sporophyte, the cycle is complete.

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• In this life cycle, the gametophyte generation is
  very small.
• For this reason, reproduction in gymnosperms
  appears to
• involve only one generation producing male and
  female sex cells.

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End