Gymnosperms

A seed plant that produces “naked” seeds

What are gymnosperms?

• Seed plants that produce seeds NOT enclosed in a protective fruit.

• Many have needle-like leaves• Deep growing root systems• Oldest type of seed plant-giant sequoias

4 groups of gymnosperms

• Cycads• Conifers• Ginkgoes• Gnetophytes

Cycads

• Grow mainly in tropical areas• Look like palm trees with cones

Conifers

• Cone-bearing plants• Most are evergreens• Pine trees, junipers, sequoias• Largest, most diverse groups

Ginkgoes

• Only one species lives today• Grew millions of years ago• Can tolerate air pollution-so planted along city

streets

Gnetophytes

• Live in hot deserts and tropical rain forest• Some are trees, others shrubs or vines

reproduction

• Most involves CONES-covered with scales• Most gymnosperms produce male and female

cones• Male cones produce pollen which contain cells

that will become sperm cells.• Female cones contain ovules which contain

the egg cell

Pollination

• Transfer of pollen from the male reproductive structure to the female reproductive structure

• Usually carried by wind• Collects on a sticky substance produced by the

ovule

Fertilization

• After pollination, the ovule will close and seal in the pollen.

• The sperm cell fertilizes the egg cell• The fertilized egg (zygote) develops into the

embryo• It can take up 2 years for the seed to mature

Germination

• Once the seeds mature, the scales open• Wind shakes the seeds out and carries them

away• If seeds land in favorable conditions, the seed

will sprout--germinate

Useful products

• Paper• Lumber• Rayon fibers• Cellophane wrap• Turpentine• Rosin• These are renewable resources!