Phylum Bryophyta - Mosses

Phylum Bryophyta - Mosses • Mosses – Introduction • There are about 15,000 species of mosses currently known. There are almost twice as many kinds of mosses as there are mammals. • Divided into three classes: Peat Mosses True Mosses Rock Mosses Phylum Bryophyta - Mosses • Lots of small, leafy green stuff gets called moss, but its not really moss. Reindeer moss- lichen Spanish moss- flowering plants Irish moss- red alga Phylum Bryophyta - Mosses • Moss gametophytes usually look leafier than those of other bryophytes. The leaves of mosses are usually very simple and just one cell thick. Some have a midrib, a thicker area that runs down the middle of the leaf. Phylum Bryophyta - Mosses • Moss gametophytes differ from those of other bryophytes in several ways. Moss gametophytes have radial symmetry, with their leaves arranged around a central axis. Gametophytes of liverworts and hornworts are flattened and have bilateral symmetry. The rhizoids that anchor moss gametophytes to the ground are multicellular. In liverworts, they are unicellular. The leaves of mosses tend to be pointier and more leafy-looking than the leaves of liverworts, which are more rounded and scale-like. Phylum Bryophyta - Mosses • Moss sporophytes look like skinny little lanterns or flags growing up off the gametophyte. The sporophyte has several parts. The sporophyte grows upward on a stalk called a seta. A chamber called a capsule forms at the end of the seta. The capsule is covered by a little hat-like piece of tissue called a calyptra. Phylum Bryophyta – Moss Life Cycle • Beginning with the germination of a haploid spore…….. • 1. The spore germinates, growing by mitosis into a filament, or strand of cells called a protonema. • As the protonema grows, it branches and forms a mat-like network. Phylum Bryophyta – Moss Life Cycle • 2. At various points along the protomena, cells divide by mitosis to produce small leafy structures that develop rhizoids and grow into the leafy gametophytes. Phylum Bryophyta – Moss Life Cycle • 3. At the tips of the gametophytes, or sometimes on special branches, cells differentiate to form gametangia. Archegonium produces the egg. Antheridia produce many sperm. Phylum Bryophyta – Moss Life Cycle • 4. When water is available, the sperm swim to the egg, attracted by substances released by the archegonia. • The sperm fertilizes the egg, forming the diploid zygote. Phylum Bryophyta – Moss Life Cycle • 5. The zygote grows by mitosis into an embryo, which breaks down cell at the base of the archegonium and then attaches itself with a knob-like mass of cells called a foot. Phylum Bryophyta – Moss Life Cycle • 6. The sporophyte grows up and out of the archegonium, taking the top with it, which forms the little hat-like calyptra. As the sporophyte grows, it develops chloroplasts, becomes green, and starts to do photosynthesis. Phylum Bryophyta – Moss Life Cycle • 7. The mature sporophyte, which consists of the capsule- also called a sporangium- supported on a seta, produces spores. The spore mother cells divide by meiosis to produce the haploid spores. Phylum Bryophyta – Moss Life Cycle • 8. When the spores are mature, the lid of the capsule, called the operculum, falls off, revealing an opening called the peristome. The spores are carried away by the wind. • Asexual reproduction can occur through fragmentation, when pieces of the gametophyte break off and then regrow into new individuals. Peat Moss • Peat moss is made up of a moss called Sphagnum that has some very unique and useful characteristics. It is used in some potting mixes to hold water. It can hold up to 25 times its own weight in water. Native Americans used it as baby diapers. When dry, it makes a good fuel. It has been used as a fuel for centuries. Used as a bandage during WW1 because it is absorbent and antimicrobial. Peat Moss • Sphagnum produces acids as it grows, making its environment acidic. The acid prevents bacteria from growing, so peat bogs are places where decomposition of dead materials happens very slowly. Perfectly preserved bodies have been found in peat bogs, like the Tollund man estimated to have lived about 400 years BC. Peat Moss When he was found, his face was clearly visible, and his clothes and hair were intact—as was the rope around his neck that was used to hang him almost 2,500 years ago. Mosses • Luminous mosses are found in caves near the entrances and in other dark, damp places. • They are called luminous because they glow an eerie golden-green in reflected light • The upper surfaces of their cells are slightly curved, and each cell functions as a tiny magnifying glass. Phylum Bryophyta • Human and Ecological Relevance Pioneer Species of Primary Succession Indicators of Surface Water Packing Material Peat Mosses - Soil Conditioner - Poultice Material - Fuel Copyright © McGraw-Hill Companies Permission Required for Reproduction or Display .

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