Plants

The Kingdom Plantae

Common characteristics

1. Multicellular

2. Eukaryotic

3. Photoautotrophic

First: Some terms to know

• Gametophyte: a multi-celled haploid body (stage) that produces haploid (n) gametes.

• Zygote: a diploid body formed when gametes fuse at fertilization.

• Sporophyte: a multi-celled diploid (2n) body that grows by mitosis from a zygote, produces spore-bearing structures.

• Spores: resting structures, able to survive harsh conditions, germinate to form gametophytes.

Adaptations to Land

• Root systems

• Shoot systems

• Vascular tissues

• Waxy cuticle for water conservation

Properties of Plants

• Photosynthetic

• Plant cells have a cell wall (cellulose)

• Organs: roots, stems, leaves

• Sessile: non-mobile, stay in one place

• Indeterminate growth

• Life cycle: Gametophyte

Sporophyte

Milestones in Plant Evolution

charophytes bryophytes lycophytes horsetails ferns cycads ginkgos conifers gnetophytes flowering plants

seed plants

plants with true leaves

vascular plants

land plants

(closely related groups)

The Non-Vascular Plants: Bryophytes

• Small, nonvascular, non-woody

• Gametophyte dominates life cycle; has leaf-like, stem-like, and root-like parts

• Usually live in wet habitats

• Flagellated sperm require water to reach eggs

Moss Life Cycle

Fertilization MeiosisDiploid Stage

Haploid Stage

malegametophytetip

femalegametophytetip

Zygote

Development of mature sporophyte (still attached to gametophyte)

Male gametophyte

Female gametophyte

Spores released

Egg

Sperm

Vascular Plants

• Majority of plants

• Have internal tissues that carry water

and solutes (Xylem and Phloem)

• Two groups

– Seedless vascular plants

– Seed-bearing vascular plants

Seedless Vascular Plants

• Produce spores but no seeds

• Main groups:

Lycophytes

Horsetails

Ferns

Life Cycle of a Fern

Seedless Vascular Plants

• Like bryophytes:

– Live in wet, humid places

– Require water for fertilization

• Unlike bryophytes:

– Sporophyte is free-living and

has vascular tissues

Rise of Seed-Bearing Plants

• Seeds appeared about 360 million

years ago

• Seed ferns and gymnosperms were

dominant at first

• Angiosperms arose later

Pollen

• Pollen grains are sperm-bearing male gametophytes that develop from microspores

• Allows transfer of sperm to egg without water

• Can drift on air currents, or be carried by pollinators

Seeds

• Ovules are female reproductive structures that become seeds

• Consist of:– Female gametophyte with egg cell

– Nutrient-rich tissue (endosperm)

– Jacket of cell layers that will form seed coat

Seed-Bearing Vascular Plants

• Gymnosperms arose first– Conifers– Others…

• Angiosperms arose later– Monocots– Dicots

Special Traits of Seed-Bearing Plants

• Pollen grains– Arise from microspores– Develop into male gametophytes– Can be transported without water

• Seeds– Megaspores inside ovules– Embryo sporophyte inside nutritive tissues

and a protective coat– Can withstand hostile conditions

Gymnosperms

• Plants with “naked seeds”

• Seeds don’t form inside an ovary

• Four groups

Conifers Ginkgos

Cycads Gnetophytes

Conifer Characteristics

• Widest known, largest number of living species

• Woody trees or shrubs

• Most are evergreen

• Bear seeds on exposed cone scales

• Most produce woody cones

Pine Cones

• Woody scales of a “pine cone” are the

parts of where megaspores formed

and developed into female

gametophytes

• Male cones, where microspores and

pollen are produced, are not woody

Pine Cones

Male and female cones

PineLife

CycleSporophyte(Pine Tree)

Female cone

Male cone

Ovule

Fertilization Meiosis

MicrosporesMegaspores

Pollen sac

Egg View insideovule

Pollen tube

Seed

Angiosperms

• Flowering plants

• Defining feature: Ovules and (after fertilization) seeds are enclosed in an ovary

• Two classes: Monocots and Dicots

Flower Parts

Pollination by animals

Life Cycle of Angiosperms

Vascular Tissues

Xylem = absorbs water and nutrients up through the roots

- movement only in the upward direction

Phloem = distributes sugars, amino acids, & organic nutrients

- movement is multi-directional

Monocots vs. Dicots

Monocots• 1 cotyledon• Parallel veins• Fibrous root• Flower parts in 3’s• Stem organization:

- Scattered bundles

Dicots• 2 cotyledons• Net-like veins• Tap root• Flower parts in 4’s / 5’s• Stem organization:

- Bundles in a ring

Monocots vs. Dicots

Monocots vs. Dicots

A Fungus is Not a Plant

There are many significant differences between fungi and plants, including

– fungi are hetertrophs

– fungi have filamentous bodies (Hyphae, Mycelium)

– fungi have nonmotile sperm

– fungi have cell walls made of chitin

– fungi have nuclear mitosis

Many fungi produce spores.