9.21: Gymnosperm Life Cycle
- Page ID
- 6665
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Of course not. But look closely at these pine cones. Notice the shape. Can you see the "petals?" They do seem oddly similar to flowers. These pine cones have a prominent role in the gymnosperm life cycle. So what is the function of a pine cone?
Life Cycle of Gymnosperms
Gymnosperms are vascular plants that produce seeds in cones. Examples include coniferssuch as pine and spruce trees. The gymnosperm life cycle has a dominant sporophyte generation. Both gametophytes and the next generation’s new sporophytes develop on the sporophyte parent plant. Figure below is a diagram of a gymnosperm life cycle.
The gymnosperm life cycle follows the general plant life cycle, but with some new adaptations. Can you identify them?
Cones form on a mature sporophyte plant. Inside male cones, male spores develop into male gametophytes. Each male gametophyte consists of several cells enclosed within a grain of pollen. Inside female cones, female spores develop into female gametophytes. Each female gametophyte produces an egg inside an ovule.
Pollination occurs when pollen is transferred from a male to female cone. If sperm then travel from the pollen to an egg so fertilization can occur, a diploid zygote results. The zygote develops into an embryo within a seed, which forms from the ovule inside the female cone. If the seed germinates, it may grow into a mature sporophyte tree, which repeats the cycle.
Summary
- In gymnosperms, the gametophyte generation takes place in a cone, which forms on the mature sporophyte plant.
- Each male gametophyte is just a few cells inside a grain of pollen. Each female gametophyte produces an egg inside an ovule.
- Pollination must occur for fertilization to take place. Zygotes develop into embryos inside seeds, from which the next sporophyte generation grows.
Review
- Describe how gymnosperms use cones to reproduce.
- Create your own cycle diagram to represent the life cycle of a gymnosperm.