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Introduction
Gymnosperms: Cone Structure
and Reproductive Cycle
• First seed plants were gymnosperms (fernlike in
appearance)
• Oldest known seeds: >350 mio years ago
(Many images removed)
Medullosa,
An early seed plant
http://commonfossilsofoklahoma.snomnh.ou.edu/medullosans1
Conifer reproduction
- In most conifers, seeds are in cones.
- Seeds are ‘naked’, not enclosed within a fruit
Conifer reproduction – cones
Cone: collection of reproductive structures on a
short axis
In most conifers, there are 2 types of cones on the
same tree.
- Pollen (♂) cones
- Seed (♀) cones
Conifer reproduction – pollen cones
Conifer reproduction – seed cones
• Pollen cones produce pollen grains, which are
dispersed by wind
• Pine seed cone; seeds develop on woody scales
• Each scale bears 2 ovules
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Conifer reproduction – seed cones
• Ovule consists of the nucellus (=megasporangium),
surrounded by a strong integument
Conifer reproduction
•Serotinous cones (e.g., Lodgepole pine and Jack
Pine).
• with opening = micropyle
• One megaspore develops into ♀ gametophyte with
archegonia
http://nswildflora.ca/species/Pinaceae/PBanksiana/species.html
Seeds of other gymnosperms
– Yew (Taxus) produces ovules at tips of shoots.
– Juniper “berries” are fleshy seed cones.
http://www.freewebs.com/berrystar/herbs.htm
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