Plant Diversity I. Terrestrial environments - deserts, grasslands, forests. 4 groups of land plants: bryophytes, pteridophytes, gymnosperms, and angiosperms

Plant Diversity I

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• Terrestrial environments - deserts, grasslands, forests.

• 4 groups of land plants: bryophytes, pteridophytes, gymnosperms, and angiosperms.

• Most common bryophytes - mosses.

• Pteridophytes - ferns.• Gymnosperms – pines, conifers.• Angiosperms - flowering plants.



Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

• Bryophytes - offspring remain attached to parent plant.

• Non-vascular plants.• Vascular plants - vascular

tissues, cells join into tubes that transport water, nutrients throughout plant body.

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http://www.science.siu.edu/landplants/Bryophyta/images/Physcomitrium.JPEG

• Ferns - seedless plants. • Seed - plant embryo packaged

along with food supply within protective coat.

• Early seed plants gave rise to diversity of present-day gymnosperms, including conifers.

• Modern plants angiosperms.QuickTime™ and a decompressor


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Fern

• Plant evolution: • 1Origin of bryophytes from algal

ancestors.• 2Origin, diversification of

vascular plants.• 3Origin of seeds.• 4Evolution of flowers.



• Plants – multicellular, derive energy and nutrition through photosynthesis.

• Plant cell walls - cellulose.• Different from algae - apical

meristems, alternation of generations, sporangia that produce walled spores.



http://www.botany.hawaii.edu/faculty/webb/BOT311/bot311-00/PlantCellWalls00/CellWallHemiLab.jpg

• Plants need to grow to maximize absorption.

• Done through apical meristems - undifferentiated cells that divide when needed.

• Located at tips of roots, shoots.



• Multicellular plant embryos develop from zygotes - stay in tissues of female parent.

• Land plants - embryophytes. • Parent provides nutrients to

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• Alternation of generations - gametophyte produces haploid gametes that get fertilized; form a diploid zygote that will grow into mature sporophyte.



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• Sporophyte produces haploid single-celled spores - grow into gametophyte.

• Spore - reproductive cell that can develop into new organism.

• Size of sporophyte and gametophyte differ in plant species.


• Bryophytes - gametophyte dominant generation.

• Pteridophytes, gymnosperms, and angiosperms - sporophyte dominant generation.



http://www.sbs.auckland.ac.nz/info/schools/nzplants/images/moss/moss_major_parts1.jpg

• Spores - haploid reproductive cells -grow into gametophyte by mitosis.

• Covered by sporopollenin – resistant to outside stress.

• Sporangia found on sporophyte - produce spores. QuickTime™ and a

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• Female gametangium (gamete producing organ) – archegonium - produces single egg cell in vase-shaped organ.

• Male gametangia – antheridia - produce many sperm cells released to environment.

• Sperm fuses with egg in archegonium. QuickTime™ and a


Female

Fusion of sperm and egg

• Land plants have cuticle – protects from drying out, microbes.

• Stomata, in epidermis of leaves allow exchange of carbon dioxide and oxygen between outside air and leaf interior.



• Land plants - true roots, stems, leaves.

• Xylem carry water, minerals up from roots.

• Dead at maturity.• Phloem - living tissue - nutrient-

conducting cells arranged into tubes distribute sugars, amino acids, other organic products. QuickTime™ and a


http://www.bbc.co.uk/schools/gcsebitesize/img/bixylemphloem.gif

• Plants also produce secondary compounds.

• Include alkaloids, terpenes, tannins, and phenolics such as flavonoids - bitter tastes, strong odors, or toxic effects.

• Some used for medicinal purposes.


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Origin of land plants

• Chloroplasts of land plants most similar to plastids of green algae.

• In both - cellulose comprises 20-26% of cell wall.



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Bryophytes

• 3 phyla - phylum Hepatophyta – liverworts, phylum Anthocerophyta – hornworts, phylum Bryophyta – mosses.

• Gametophytes dominant phase of life cycle.



• Bryophytes anchored by tubular cells or filaments of cells - rhizoids.

• Lack conducting tissues to distribute water and organic compounds within gametophyte – very small.


http://userwww.sfsu.edu/~biol240/labs/lab_10plantoverview/media/rhizoids.jpg

• “Leaves” of most mosses lack a cuticle and are only 1 cell thick – allow quick absorption from surroundings.

• Mature gametophores of bryophytes produce gametes in gametangia.


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• Archegonium - single egg.• Antheridia - many flagellated

sperm. • Sperm swim toward archegonia,

drawn by chemical attractants.• Zygotes and young sporophytes

retained and nourished by parent gametophyte.



• Moss sporophytes consist of foot, elongated stalk (seta), and sporangium (capsule).

• Foot gathers nutrients and water from parent gametophyte via transfer cells.

• Stalk conducts materials to capsule.

• Capsule – disperse spores.



• Common in wetlands, wind dispersal allows for inhabiting many different areas.

•Sphagnum, wetland moss, abundant and widespread – forms deposits of undecayed organic material – peat.

• Forms peat bogs. QuickTime™ and a decompressor


• Vascular plants have food transport tissues (phloem) and water conducting tissues (xylem) with lignified cells.

• 1st vascular plants, pteridophytes, were seedless.


http://www.florelaurentienne.com/flore/Groupes/Pteridophytes/images/Adiantum_pedatum_940528_21_800.jpg

Seedless Vascular Plants•Cooksonia, extinct plant over 400

million years old, earliest known vascular plant.

• Seedless vascular plants, pteridophytes consists of 2 modern phyla:

• Phylum Lycophyta – lycophytes.• Phylum Pterophyta -- ferns, whisk

ferns, and horsetails.


Cooksonia

• Lycophytes have small leaves (microphylls) with single unbranched vein.

• Leaves of other vascular plants, megaphylls much larger and highly-branched.


• Homosporous sporophyte produces a single type of spore.

• Heterosporous sporophyte produces 2 kinds of spores.

• Megaspores - females gametophytes.

• Microspores - male gametophytes.



Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 29.23

• Modern lycophytes include tropical species that grow on trees as epiphytes, using the trees as substrates, not as hosts.

• Specialized leaves (sporophylls) bear sporangia clustered to form club-shaped cones.



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• Phylum Pterophyta – ferns and relatives.

• 1Psilophytes - whisk ferns.• 2Sphenophytes – horsetails - often

found in marshy habitats and along streams and sandy roadways.

• Roots develop from horizontal rhizomes that extend along ground. QuickTime™ and a decompressorare needed to see this picture.

• 3Ferns - horizontal rhizomes.• Fern leaves (fronds) may be

divided into many leaflets. • Produce clusters of sporangia

(sori) on back of green leaves (sporophylls) or on special, non-green leaves.

• Dispersed by wind.



Documents

Plant Diversity I. Terrestrial environments - deserts, grasslands, forests. 4 groups of land plants: bryophytes, pteridophytes, gymnosperms, and angiosperms