Multicellular Photosynthetic Autotrophs edit

Plants edit

Multicellular
Cellulose cell walls
Chlorophylls a and b
Develop from embryophyte
Alternation of generations
Major food source for terrestrial life
Atmospheric O2 and CO2 balance
Coal deposits
Intimate association with mycorrhizal fungi
>250,000 species (~500,000?)
Taxonomy
- State of flux
DNA sequencing
Developmental studies
- Division (old literature) = phylum (new literature)
- ~12 phyla, 9 of which are vascular plants

Plant phyla edit

Phyla are 12 groupings

Plant evolution edit

Evolved from green algae, likely related to charophytes
Evidence
- DNA sequences
- homologous chloroplasts: chlorophyll b and beta-carotene; thylakoids in grana;
- Cellulose in both groups; also peroxisomes
- Mitosis and cytokinesis similar
- Sperm ultrastructure

Terrestrial adaptations edit

Stomata: pores in leaves for exchange of gases; prevent desiccation
Secondary metabolites:
- cuticle: waxy coating to prevent H2O loss
- lignin: hardens wood
- sporopollenin: resistant polymer; coats pollen
- predator defenses
Embryonic development
- gametangia in early plants
- spores; seeds
Mycorrhizae
Water/food conducting systems

Plant phylogeny edit

Plant life cycles edit

Alternation of generations
Sporophyte
- diploid
- produces spores in sporangia
Gametophyte
- develops from spore
- haploid
- produces gametes in gametangia
Haplodiplontic life cycle

Moss life cycle edit

Moss has no vascular tissues or flowers. It is a thallus plant (it does not have true roots,stem and leaves). It does not produce seeds like the angiosperm.

Vascular plants edit

Most have roots
Aerial shoot systems
Vascular tissue
- xylem: water, mineral transport
- phloem: food transport
Lignin
Branched sporophyte is dominant stage
- amplified production of spores
- evolution of complex plant bodies
Dominated Carboniferous (360 my)

Vascular plant life cycles edit

Homosporous (single type of spore)
Heterosporous (two types of spore)

Pterophyta (ferns) edit

Non-seed plant
Sporophyte conspicuous (vascular tissue)
Rhizome: ground stem, roots
Fronds: leaves
Sori: clusters of sporangia
Motile sperm require external water for fertilization
Originated in Devonian, 350 my

Tree fern Fern life cycle

Non-seed plants, continued edit

Lycophyta: club mosses
- E.g., Lycopodium (“ground pine”)
- Many species became extinct 270 my, once dominant (coal formations)
- Gametophyte non-photosynthetic, nourished by fungi
Arthrophyta: horsetails
- Equisitum
- Some fossil forms (300 my) were tree-size (coal)
- Photosynthetic stems, no leaves
- Silica deposits in epidermal cells

Seed plants edit

1st appeared in Devonian, 360 my
Seed develops from ovule, protects embryo
- withstands drought
- dispersal is enhanced
- no immediate need for water for germination
Heterosporous
- male gametophyte: arise from microspores
- female gametophyte: arise from megaspores in ovule in ovary
Two groups
- gymnosperms
- angiosperms

plant

Sporophyte/gametophyte edit

Megasporangium (nucellus) edit

Key to seed development
Nucellus: solid, fleshy, surrounded by integuments derived from sporophyte (seed coat)
Entire structure called ovule
Flower may have many ovules

Pollen edit

Develop from microspores, become male gametophyte
Protected by sporopellenin
In most plants, sperm lack flagella (loss)
Many mechanisms to transport pollen
- wind
- insects, birds,

Gymnosperms edit

“naked seed”
- ovule not fully enclosed by sporophyte at time of pollination
Conifers, cycads, gnetophytes, Ginkgo
Small, inconspicuous plants to giants like sequoia
Conifers: to carry cones fv
- male cones, Female conesvv
- evergreen

Pine life cycle edit

Other Coniferophyta edit

Cycadophyta: cycads
- tropical, subtropical
- flagellated sperm
Gnetophyta
- e.g., Ephedra, Mormon Tea
Ginkgophyta: Ginkgo
- only one surviving species
- diecious (separate % and &trees)

Other gymnosperms edit

Angiosperms edit

Flowering plants, Anthophyta
- monocots- single seed leaf (grasses, lilies, etc.)
- dicots- two seed leaves (roses, pulses, maples)
More specialized xylem (water transport)
- vessel elements
- fiber cells
Fossils date to 130 my
Animal (e.g., insect) coevolution

Monocots vs dicots edit

Earliest angiosperm edit

What is earliest angiosperm?
Recent analysis of nucleotide and amino acid sequences suggests that Amborella, a tropical plant found only on the island of New Caledonia, is closest relative to flowering plants

Angiosperm flower edit

Angiosperm life cycle edit

This text is based on notes very generously donated by Paul Doerder, Ph.D., of the Cleveland State University.

General Biology/Classification of Living Things/Eukaryotes/Plants

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