Plants: The simple ones Non-seed, Non-vascular Mosses, Liverworts, and Hornworts: Bryophyta

Basic Moss Structure Mosses, or bryophytes, are not as common or as widespread as vascular plants because their structure and life cycle requires a close association with water. Mosses absorb nutrients, instead through their leaf-like structures which tend to lie on the ground. Mosses don’t have true roots, but structures called rhizoids which anchor the stem to the soil, but lack transport tissue.

Bryophytes Because water isn’t available everywhere, bryophytes are limited to only the moist habitats by streams, rivers, or rain forests. As mosses are nonvascular, their prone position allows for the easy movement of water and nutrients across membranes. Specialized transport cells known as hydroids and leptoids, which are analogous to the xylem and phloem of vascular plants, are found at the center of the stem.

Alternation of Generations Sexual, and Asexual Alternation of Generations As is true with all plants, the life cycle of these nonvascular plants includes an alternation of generations between the diploid sporophyte and the haploid gametophyte. 2N = diploid sporophyte Gemmae are a means of asexual reproduction found in many bryophytes. Gemmae are specially produced clonal plant fragments.  N = haploid gametophyte fragmentation - pieces of the gametophyte breaking off  and generating a new plant Asexual reproduction in plants is also known as vegetative reproduction

Dominant Gametophyte The nonvascular plants include the only plants that have a dominant gametophyte stage. The haploid stage occurs when a multicellular haploid gametophyte develops from a spore and produces haploid gametes. Sporophytes (diploid) grow attached to and depend upon the gametophyte (haploid) for water and other substances. Some gametophytes contain separate male and female sex organs and are actually plants of separate gender. These are said to be dioecious. Those that contain both are said to be monoecious.

A protective structure know as a gametangia (on the surface of the gametophyte) produces gametes. In this particular plant, both male and female parts are present in separate areas. What special name is this type of plant given? Male gametangium (aka antheridium) Female gametangium (aka archaegonium) Monoecious Produces flagellated sperm that swim through water to fertilize the eggs produced by the female gametangium. Produces the eggs which are fertilized by the sperm produced in the antheridium Once fertilized, the diploid zygote grows from the top of the female gametophyte.This is called the sporophyte, which contains haploid spores.

Moss Life Cycle Male sex organ Female sex organ

Liverworts also have rhizoids instead of roots to anchor them Little or no vascular tissue in leaves or stems do not contain stomata, so they shrivel up when dehydrated (no transpiration) For the exchange of gases necessary for photosynthesis, each cell has a pore-like opening through which CO2 and O2 move.

Hornworts Role of Bryophytes Many are pioneer plants, growing on bare rock and contributing to soil development. In bogs and mountain forests they form a thick carpet, reducing erosion. In forest ecosystems they act like a sponge retaining and slowly releasing water Indicator species. Lacking a cuticle and transport tissue they readily absorb whatever is around them and can serve as bioindicators of pollution and environmental degradation  

Vascular, Non-seed Plants Tracheophytes: vascular plants The Psilophyta The Lycophyta The Sphenophyta Whisk fern Epiphytes Club mosses Horsetails Strobili Strobili These simple plants are the first true vascular plants. They are still tied to the watery environment as their main form of sexual reproduction depends upon sperm swimming to the egg. They are spore producers (non-seed)

The Pterophyta “The Ferns” Fern Rhizomes Fern Fronds Fern Frond Fiddlehead The ferns have a dominant sporophyte generation. It is what you “see”. “The Ferns” Fern Rhizomes Fern Fronds Root-like structures In ferns, as with all other terrestrial plants, the sporophyte generation is dominant, and 2n…while the gametophyte is tiny, and n.

Alternation of Generation Fern Reproduction Sorus (Sori) Archegonium Antheridium Fern Gametophyte, or Prothallus