Conifers BIOL 1407
Dec 28, 2015
Conifers
BIOL 1407
Seed Plants
• Vascular Tissue
• Produce seeds– Dispersal of
offspring
• Produce pollen• Sperm transfer
without water
Seed Plants• Sporophyte
dominant• Gametophytes
– Greatly reduced in size
– Dependent on sporophyte
Seed Plants• Heterosporous
– Megaspore• Grows into
female gametophyte eggs
– Microspore• Grows into male
gametophyte sperm
– Photo Credit for Ovulate Cone: Dr. Stephen Bostic, ACC
– Circled area: Ovule
Pollen Production
• Pollen cones have microsporophylls
• Each microsporophyll has microsporangia
• Photo Credit for Immature Male Pine Cones: Menchi, Wikimedia Commons
Pollen Production• Meiosis occurs
within microsporangia microspores
• Photo Credit for Staminate Cone: Dr. Stephen Bostic, ACC
• Microsporangium circled in red• Microsporophyll at tip of yellow pointer• Microspores circled in pink
Pollen Production
• Microspores grow into male gametophytes
• Male gametophyte = pollen grain
Pollination
• Pollen is released • Travels from male to
female• Pollination occurs
when pollen grain lands on female
• http://www.youtube.com/watch?v=Bwl4g48-uIE
Pollen Germination
• After landing pollen coat breaks open
• 1 cell produces pollen tube
• Photo Credit: Dr. David Byres, Florida Community College at Jacksonville
Pollen Germination
• A different cell produces 2 sperm cells by mitosis
• They will move down pollen tube as it grows
• Photo Credit: Dr. David Byres, Florida Community College at Jacksonville
Pollen Germination
• Pollen tube digests its way through female tissues to reach the egg
Ovules
• Ovulate cones have megasporophylls
• Each megasporophyll has ovules containing megasporangia
• Photo Credit for Immature Female Ponderosa Pine Cones: Susan McDougall @ USDA-NRCS PLANTS Database
Ovules
• Meiosis occurs within megasporangium forms 1 megaspore and 3 haploid nuclei (degenerate)
• Photo Credit: Dr. Stephen Bostic, ACC• Megasporangium circled in red• Megasporophyll at tip of yellow pointer
Ovules
• Megaspore grows into female gametophyte
• Female gametophyte makes 1-2 eggs by mitosis
Ovules
• Integuments surround female gametophyte
• Micropyle lets pollen reach female gametophyte
Ovules Seeds
• Integuments seed coat
• Female gametophyte food supply
• Fertilized egg embryo
Seeds
• Dispersed by:– Wind– Animals– Water– Mechanical
• Photo Credit for Pitch Pine Seeds: Steve Hurst @ USDA-NRCS PLANTS Database
Types of Seed Plants
• Gymnosperms– Naked Seeds– Not enclosed in
ovaries– No fruits or
flowers
Types of Seed Plants
• Angiosperms– Flowering Plants– Seeds enclosed in
ovaries– Fruits and flowers
Modern Gymnosperms• Conifers
– Oldest living plants
– Largest living plants
– Widespread– Reproductive
structure: Cones
Modern Gymnosperms
• Cycads– Wiry leaves– “Sago palms”
• Ginkgos• Deciduous
trees• One species• Herbal
supplement
Modern Gymnosperms
• Gnetophytes– Ephedra
(Mormon tea)– Welwitschia
The End
Unless otherwise specified, all images in this presentation came from:
Campbell, et al. 2008. Biology, 8th ed. Pearson Benjamin Cummings.