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.