Reproductive Life Cycles of Vascular Plants. Plant life cycles are characterized by alternate sporophytic and gametophytic generations.

Transcription

1 Reproductive Life Cycles of Vascular Plants Plant life cycles are characterized by alternate sporophytic and gametophytic generations.

2 Reproductive Life Cycles of Vascular Plants From the National Botanic Garden

3 Reproductive Life Cycles of Vascular Plants Plants Vascular plants are separated into those that disseminate the next generation by spores or those that produce seeds. Non-vascular Mosses 400 million years ago Vascular Seedless plants 300 million years ago lycopods horsetails ferns Seed plants cycads 200 million years ago ginkgo conifers 100 million years ago angiosperms 55 million years ago dicots monocots

4 Mosses Mosses are non-vascular, spore producing plants.

5 Reproductive Life Cycles of Vascular Plants The seedless vascular plants reproduce from spores. Plants Non-vascular Mosses 400 million years ago Vascular Seedless plants 300 million years ago horsetails (Equisetum) wiskferns (Psilotum) lycopods (Lycopodium) Selaginella ferns The spore is a protective structure that is tolerant of environmental conditions, germinating when conditions are conducive for the gametophytic generation (usually wet conditions).

6 Vascular seedless plants The U.S. National Botanic Garden s depiction of the late Carboniferous Swamp forest. The dominant tree species are club mosses (Lycopodium) and horsetails (Equisetum).

7 Vascular seedless plants Except for the tree ferns, the large treelike members of the vascular, seedless plants from the Carboniferous period are extinct and only recorded in fossils. Lycopod Tree fern Gymnosperm Gymnosperm Lycopod Horsetail

8 Vascular seedless plants The majority of these species went extinct in the Paleozoic era (248 million years ago). Lycopodium Equisetum Ferns

9 Lycopodiaceae Lycopodium (Club mosses)

10 Lycopodiaceae Lycopodium (Club mosses) The modern day club mosses survived as much smaller versions of their extinct relatives. Most temperate club mosses are under a foot tall.

11 Lycopodiaceae Lycopodium (Club mosses) Club mosses are homosporous producing female and male gametophytes from the same spore. Spores are produced on sporophylls in terminal strobili (arrows).

12 Some tropical lycopods can reach three or more feet tall. Lycopodiaceae Lycopodium (Club mosses) Lycopodium squarrosa Lycopododiella cernua

13 Selaginella Selaginella are heterosporous. This means they produce a different spore for the male (microspore) and female (megaspore). These are produced from their respective microsporophylls (males) and megasporophylls (female) within the same strobilus (arrow).

14 Horsetails - Equisetum Extinct horse tails could grow 50 feet tall, but today s horsetails are usually under 6 feet tall and may be the oldest surviving plant genus. Horsetails are homosporous with sporangia produced within the terminal strobili.

15 Ferns Ferns are abundant in the fossil record and are still abundant today. They are a diverse group represented by terrestrial, epiphytic, vine and tree types of ferns. Staghorn fern (Platycerium ) Cinnamon fern (Osmunda) Climbing fern (Lygodium) Tree fern (Cyathea)

16 Fern life cycle Generalized life cycle for ferns

17 Fern life cycle Most ferns produce spores on the undersides of the fronds (like bird s nest fern) or on specialized fertile fronds (like cinnamon fern). Asplenium Cinnamon fern (Osmunda cinnamomea )

18 Fern life cycle Diversity of sporangia in different ferns.

19 Fern life cycle Sporangium containing spores are often produced on the underside of the leaves.

20 Fern life cycle Sporangium open to release spores. Sporangia on the underside of the frond. Sporangia opening to release spores. Single spores.

21 Fern life cycle Spores are produced by meiosis. Sorus Spores Sporangium

22 Fern life cycle Gametophytic cycle Spores Protonema Rhizoids

23 Fern life cycle Gametophytic cycle Prothallus Prothallus Archegonium Antheridium Rhizoids

24 Fern life cycle Archegonium

25 Fern life cycle Archegonium Egg

26 Fern life cycle Antheridium

27 Fern life cycle Antheridium Sperm

28 Fern life cycle Egg Archegonium Sperm

29 Fern life cycle Young Sporophyte Sporophyte Prothallus Roots Rhizoids

30 Fern life cycle Young Sporophytes commercially produced.

31 Mature Sporophyte with leafy fronds and spore producing leaves. Fern life cycle