Continuing Trends in Plant Continuing Trends in Plant EvolutionEvolution

• Reduction of water-dependent gametophyte

• Vascular tissue – improved water/food transport

• More efficient roots, stems, leaves* Tissues* Stomates

Green: all these are in sporophyte

Reduction of gametophyteSpecialization in sporophyte

Vascular tissueVascular tissue

• In sporophyte

• Interconnects all plant organs

• Xylem - water

• Phloem - sugar

Complex leavesComplex leaves• Tissues

• Stomates

Plant classification reviewPlant classification review

• 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

Seedless Vascular PlantsSeedless Vascular Plants

• Ferns, horsetails, club mosses, whisk ferns

• Sporophyte dominant

• Gametophyte small but still tied to water

• Dominant plants from late Devonian through early Permian* Equatorial coal forests

• Today somewhat marginal, but successful

• Heterospory in some (next time)

Fern Life CycleFern Life Cycle

Gametophyte

Fertilizatio

n

Sporophyte

Meiosis

Fern gametophytes …

… with young sporophytes

Mature fern sporophyte …

… with clusters of sporangia

Whisk Fern, Psilotum

Club moss, Lycopodium

Horsetail, Equisetum

Carboniferous (-300 my) coal forest model