PlantsPlants

• Characteristics• Plant evolution• Lower plants

Hornwort

Orchid

• Photosynthetic autotrophs • Eukaryotic• Chemistry same as for green algae

* Cell walls* Pigments

• Multicellular* Tissues & organs* Embryos

Characteristics of KingdomCharacteristics of Kingdom

• Life cycle – alternation of generations

Diploid sporophyte meiosis

zygote sporesfertilization gametes Haploid gametophyte

Characteristics of KingdomCharacteristics of Kingdom

The Plant Life cycleThe Plant Life cycle• Asexual reproduction common• Sexual cycle involves alternation of two

generations* Gametophyte – gametes, dependent on water

(at first)* Sporophyte – spores, adapted to dry condition

• Trend in evolution – reduction of the gametophyte (increased importance of sporophyte)

• Produced by meiosis from sporophytes

• Haploid reproductive (dispersive) cells

• Grow into a gametophyte by mitosis

• Covered by sporopollenin

Plant sporesPlant spores

Plant gametesPlant gametes

• Produced by gametophytes by mitosis

• Eggs & sperm• Fertilized egg (zygote)

grows into sporophyte

Fern egg & sperm

Plant DevelopmentPlant Development

• Embryos* Young

sporophytes develop from zygotes

* Protected and nurtured by parent

Plant BodyPlant Body• Root / Shoot• Meristems

* growing points* root/shoot tips* (woody plants) –

sideways to form wood* indeterminate growth

Evolved from Evolved from Charophycean Charophycean Green AlgaeGreen Algae

• Mid Paleozoic• Strong similarities• Differences

Chara

ColeochaeteA Coleochaete B Parka (Ordovician)From Berkeley Time Machine

Plant classificationPlant classification

• Bryophytes – no seeds, no roots, no vascular* Mosses, liverworts, hornworts

• Seedless, vascular plants – no seeds* Ferns, horsetails, club mosses, whisk ferns

• Gymnosperms - seeds & cones* Conifers, cycads, ginkgo, gnetophytes

• Flowering plants – seeds, flowers & fruits* Primitive, Monocots, Dicots

Non-vascular plantsNon-vascular plants“Bryophytes”“Bryophytes”

• Mosses, liverworts, hornworts

• Gametophyte dominant• No roots – rhizoids• Often dependent on

available moisture• Occupy ecological niches

no other plants do• Represent first plants

Moss

Hornwort

Liverwort

Phylum Bryophyta – MossesPhylum Bryophyta – Mosses

• Leafy gametophytes• Sporophytes with complex teeth• Evolutionarily distinct group from other

bryophytes

Moss Life CycleMoss Life Cycle• Sporophyte

* Zygote* Embryo nurtured by gametophyte* Mature sporophyte with

sporangium

• Gametophyte* Spore* Protonema* Leafy gametophyte* Gametes eggs & sperm

Sporophyte

Gametophyte

Moss Life Moss Life CycleCycle

Spores

Protonema

Male leafy gametophyte

Female leafy gametophyte

Moss Life Moss Life CycleCycle

Sperm from antheridia

Egg in archegonium

Leafy gametophytes

Moss Life Moss Life CycleCycle

Fertilizatio

nZygote

Embryo

Young sporophyte

Meiosis to form spores within sporangium

Spore dispersal by wind

Gametophyte

Sporophyte

“First thread” stage

Spores

Sperm from antheridia

Egg in archegonium

Fertiliz

ation

Zygote

EmbryoM

eiosis

Moss Life Moss Life CycleCycle

Moss linksMoss links

• UBC Moss Class• Microscopy UK

Phylum Hepatophyta - Phylum Hepatophyta - LiverwortsLiverworts

• Sporophyte simpler than mosses• Leafy• Thallose

Phylum Anthocerophyta - Phylum Anthocerophyta - HornwortsHornworts

• Sporophyte linear tube with meristem at base• Thalloid• Closest bryophyte to ancestor of other plants

Moss, Rhizomnium

Moss, Tortula, whole leaf

Sphagnum bog

Sphagnum = Peat Moss

Thallose liverwort Marchantia

Leafy liverwortLophocolea

Hornwort, Anthoceros