Seedless plants ; plant diversity

colonizatino of land

There was no soil on the land 488 mya; Rocks, beaches, ponds, oceans

• There were no insects or other land animals; No polinators

• Fungi were probably already on the land along with bacteria, archaea and protists; Fungi helped make nutrients and water available to plants

Issues plant overcome on land

water loss, Protection from the harmful effects of the sun, UV rays cause DNA damage, and Ability to effectively disseminate gametes for production

Tracheophytes

have specialized vascular tissue for transport over long distances through plant body. Cuticle and stomata found in all vascular plants

Bryophytes ( mosses )

are limited in size because they lack vasculature.

Haplodiplontic life cycle

• Multicellular haploid and diploid life stages

• Also called the Alternation of Generations

• All land plants are —

• Gametophyte and sporophyte are separate individuals.

Sporophyte ( multicellular diploid stage )

• Within sporangia, diploid spore mother cells (sporocytes) undergo meiosis

• Produces 4 haploid spores by meiosis

• First cells of the gametophyte generation

Gametophyte ( multicellular haploid stage )

• Within gametangia gametes are produced by mitosis

• Gametes from different plants fuse to form diploid zygote

• Zygote is first cell of sporophyte generation

Adaptations to terrestrial life

Protection from desiccation and harmful effects of the sun

• Waxy cuticle and stomata

• Evolutionary shift to dominant diploid generation (sporophyte), meaning disastrous recessive mutations are masked

Mosses

▪ Large gametophyte

▪ Small, dependent sporophyte

Angiosperms ( flowering plants )

▪ Small, dependent gametophyte

▪ Large sporophyte

Mosses ( phylum bryophyta )

• Gametophytes consist of small, leaf-like structures around a stem-like axis

• Not true leaves – no vascular tissue

• Anchored to substrate by rhizoids (not true roots)

• Multicellular gametangia form at the tips of gametophytes: Archegonia and Antheridia

Archegonia

Female gametangia

Antheridia

Male gametangia

Male gametangia: Antheridia

• Inconspicuous

• Grows on male gametophyte

Sporophyte (2n)

• Extension of the Archegonia (female gametangia)

• Grows only on the female gametophyte

Gametophyte (1n)

• Majority of Life Cycle

• Photosynthetic

• Male and Female plants

Xylem

Conducts water and dissolved minerals upward from the roots.

Phloem

• Conducts sucrose and hormones throughout the plant

• Develop in sporophyte (2n) but not gametophyte (n)

• Enable enhanced height and size in the tracheophytes

Leaves of tracheophytes

• Increase surface area for photosynthesis

• Evolved twice

• Euphylls (true leaves) found in ferns and seed plants

• Lycophylls found in lycophytes

Roots of Tracheophytes

Provide transport and support. Gametophyte is reduced in size relative to the sporophyte

Pterophytes

vascular plants, also known as "vascular cryptogams," that reproduce via spores instead of seeds, including ferns, club mosses, and horsetails. 

Fern gametophyte

• Spores germinate into gametophyte

• Flagellated sperm requires water

• Remnant of spore coat