GENERALITIES of the PLANT KINGDOM

• Multicellular eukaryotes that are photosynthetic and autotrophic

• Most are terrestrial (some have returned to water)

• Plants are immobile evolved to cope with stress: – water loss, consumers, mechanical damage, temperature

extremes, pathogens, odd soils, etc.

• Terrestrial plants evolved from aquatic green algae

Features Shared In Common with Green Algae

• Pigments: Chlorophyll a & b; carotenoids

• Food Reserve: Starch

• Cell Walls: Cellulose

• Cell Division: Cell Plate

• Body Structure: Multicellular

• Life Cycle: Heteromorphic Alternation of Generation

• Sexual Reproduction: Oogamy

Division Chlorophyta (green algae) Order Charales features: multicellular, chlorophyll a, b, and carotenoids, starch storage, cellulose walls

Bryophytes Pteridophytes

In Aquatic Habitat

• All Cells Surrounded or Close to Water

• Dissolved Minerals

• Dissolved CO2 and O2

• Water Supports Weight of the Plant

• Unicellular Reproductive Structures

• Motile Gametes

• All Cells Photosynthetic

Evolutionary steps for the colonization of land:

• How to disperse gametes in drier environment

• How to protect embryos from drying out

• How to take up water and nutrients from below ground

• How to take up CO2 from the air

• How to transport water and nutrients long distances

Adaptations to Land Correlated with Development of Structures to Circumvent Water Requirements:

• Epidermis: cuticle (cutin), stomates

• Vascular Tissue: Xylem (water conduction), Phloem (carbohydrate conduction)

• Roots

• Lignin - found in all vascular plants, reinforces cell walls

• Multicellular gametangia: Antheridium (sperm), Archegonium (egg)

• Embryo Develops Within the Archegonium

Pangaea (meaning "all lands" in Greek)

Silurian land plants (425 - 408 MYA)

Devonian land plants (408 - 362 MYA)

Carboniferous land plants (362 - 290 MYA)

Permian land plants (290 - 245 MYA)

The warm zone spread in the northern hemisphere, where extensive dry deserts appeared. The rocks formed at that time were stained red by iron oxides, the result of intense heating by the sun of a surface devoid of vegetation cover. The old types of plants and animals died out.

Triassic land plants (245 - 208 MYA)

Jurassic land plants (245 - 208 MYA)

Gametophyte (1n)

Sporophyte (2n)

Ca. 0.5 cm long

Bryophytes

Mosses, liverworts and hornworts

Reproduce by spores

Reproduction dependent on water

No true vascular system, no hard tissues, therefore they remain small

Vascular Plants (all the rest = ferns, gymnosperms & angiosperms)

Have true roots, leaves, & vascular tissuesProduce hard or lignified tissues

xylem

phloem

Seedless Vascular Plants: Ferns & allies

Have vascular tissue & true rootsReproduction depends on waterReproduce w/ spores

Evolution of seed plants: Gymnosperms & Angiosperms-Reproduction independent of water

- Sperm enclosed in pollen; dispersed by wind, animals, etc- Eggs enclosed in protective ovule – matures into a seed

-Seeds are highly protected embryos - embryo protected (cones, fruits, etc) - often specialized dispersal (animal, water, wind)- Woody tissues common

Gymnosperms‘Naked seed’Old lineage; 700 species todayAdaptive radiation during Earth’s dry periodsNew invention

- true seeds! protects embryo

Conifers are largest group - make male & female cones

Angiosperms Most recently derived group

- 300,000 - 450,000 species- Two main groups:

1. eudicots2. monocots

New Innovations:-Flowers-Fruit

monocots

eudicots

Almost all angiosperms fall naturally into two groups (clades), monocots (one cotyledon, or seed leaf) and dicots (two cotyledons).

A few dicots (early lineages) do not form a clade, but the huge majority that do are called true dicots, or eudicots.

Angiosperms

monocots

eudicots