What is a plant?

• Multicellular• Eukaryotic cell• With cell wall of cellulose• Waxy, protective coating called cuticle• Usually contains chlorophyll for its role as

an autotroph (photosynthesis)

Plant StructuresExternal plant structures such as leaves, stems, roots, flowers, fruits, and seeds are known as plant organs. Each organ is an organized group of tissues that works together to perform a specific function. These structures can be divided into two groups: sexual reproductive and vegetative. Sexual reproductive parts produce seed; they include flower buds, flowers, fruit, and seeds. Vegetative parts include roots, stems, shoot buds, and leaves; they are not directly involved in sexual reproduction. Vegetative parts often are used in asexual forms of reproduction such as cuttings, budding, or grafting.

Alternation of Generations

Reproduction in Plants

Archegonia/Antheridia

e.g., Eggs/Sperm

Forms a Zygote

For growth

For growth

Sporophyte

• “spore plant”• Diploid state• Many common plants

have this as their dominant form

Sporangium

• Specialized organ• Diploid cells• Produces hapliod

spores to release to the environment

Meiosis in Sporangium

• Reduction division• Starts with diploid

number, finishes with haploid number in the new cells (spores)

Spore

• Haploid asexual reproductive cell

• Released into the environment

Mitosis

• Growth of cell by replication of heredity and cell division into a multi-cellular organism

Gametophyte

• “gamete plant”• Produces gametes (sex

cells) for sexual reproduction

• Eggs from archegonia• Sperm from the

antheridia

Fertilization

• Sperm nucleus unites with egg nucleus deep in the ovary of the plant

Mitosis

• Growth of cell by replication of heredity and cell division into a multi-cellular organism

This multicellular organism is the next generation of sporophyte…..you are

back to square one!

Archegonia/Antheridia

e.g., Eggs/Sperm

Forms a Zygote

For growth

For growth

Plant Phylogeny

• Bryophyta – nonvascular, non-seed plants like mosses and liverworts

• Psilophyta – non-seed vascular plants like tropical/subtropical whisk ferns

• Lycophyta – non-seed vascular plants like club mosses

• Sphenophyta – non-seed vascular plants like horsetails

Plant Phylogeny (cont.)

• Pterophyta – non-seed vascular plants like the ferns

• Cycadophyta – vascular seed plants like the palm-like cycads

• Gnetophyta – unusual, distinctive vascular seed plants like Welwitschia

• Ginkgophyta – very rare vascular seed tree with fan-shaped leaves (1 species)

Plant Phylogeny (cont.)

• Coniferophyta – cone-bearing vascular seed plants like pine trees

• Anthophyta – flowering vascular seed plants like roses (dicots) and lilies (monocots)

Bryophyta

• Non-vascular, so…….• Live in moist sheltered places• Non-seed• Mosses, hornworts, and liverworts• Plant life cycle needs water for sperm• Vegetative reproduction also

• 1 = sporophyte• 2 = gametophyte• 3 = sporangium case• 4 = stalk

Ferns and their allies

• Vascular plants (major advancement) • need water for reproduction• Seedless• Alternation of Generations• Ferns, club moss, horsetails• The beginnings of true organs

Roots to anchor, absorb water and minerals, and store food

Leaves for photosynthesis and storage of food

Stems for support, storage, and transport of water up and food down

(Flowers for reproduction, yielding the fruit in seed plants)

SporophyteGametophyte with young

sporophyte

Seed Plants

• Vascular• Produce seeds (major advancement)• Gymnosperms (bear seeds naked on bracts

of cones) and Angiosperms (flowering plants with seeds in tissues)

• Free of water because male gametophyte is in pollen grain carried by wind, water, insects, or small animals

Gymnosperms

• Cone bearers• Gnetophytes, cycads, gingkoes, conifers• Alternation of Generations

“Naked Seeds”

Seeds lying uncovered on the bract

Alternation of Generations

Angiosperms (Phylum Anthophyta)

• Flowering plants• Vascular seed plants• Fruits with seeds

– Dry fruits– Fleshy fruits

• Most of the commons plants we know• Alternation of Generations

Alternation of Generations

The Typical Flower (reproductive organ)

A comparison of Classes Dicotyledonae vs Monocotyledonae

XYLEM AND PHLOEMXYLEM AND PHLOEM XYLEM = “water UP” XYLEM = “water UP” PHLOEM = “food DOWN”PHLOEM = “food DOWN”

VASCULAR BUNDLES

HERBACEOUS STEM - GREEN WOODY TREE

Plant Life Spans

• Annual – germinate, grow, flower, seed, and die in one growing season

• Biennial – germinate, grow, develop first season; flower, seed, and die second season

• Perennial – live and flower (seed) for many seasons