Chapter 16 - Bryophytes

Lecture 12: Bryophytes - Chapter 16 Peat Moss Sphagnum

Overview of Bryophytes

• Introduction to Bryophytes:

  • Comprises about 23,000 species including mosses, liverworts, and hornworts.

  • Habitats range from sea level to elevations of over 5,500 m.

  • Bryophytes are among the first land plants, existing for over 400 million years.

  • Often associated with mycorrhizal fungi, enhancing nutrient absorption through rhizoids.

• Characteristics:

  • Nonvascular plants lacking true xylem and phloem.

  • Some have specialized water-conducting cells (hydroids) and few with food-conducting cells (leptoids).

  • Exhibit an alteration of generations with a dominant haploid gametophyte stage.

  • Peat mosses (Sphagnum) are ecologically significant in carbon storage in bogs.

Alternation of Generations

• Definition:

  • A life cycle in plants involving alternation between diploid sporophyte and haploid gametophyte generations.

• Sporophyte (2n):

  • The spore-producing phase of the life cycle, dependent on the gametophyte.

• Gametophyte (n):

  • The gamete-producing stage, which is typically independent and more prominent in bryophytes than in vascular plants.

• Meiosis and Fertilization:

  • Meiosis results in the production of haploid spores from sporophytes.

  • Fertilization results in the formation of a diploid zygote, which grows into a sporophyte.

Plant Structure and Reproduction

• Bryophyte Structures:

  • Liverworts (Phylum Hepaticophyta):

    • Approximately 6,000 species.

    • Two main forms: Thalloid liverworts (flattened lobed structures) and leafy liverworts.

    • Reproductive structures consist of gametangia (antheridia and archegonia).

  • Hornworts (Phylum Anthocerophyta):

    • 100 species characterized by horn-like sporophytes.

    • Thalli with pores and cavities often housing nitrogen-fixing bacteria.

  • Mosses (Phylum Bryophyta):

    • Around 9,500 species, classified into Peat Mosses, True Mosses, and Granite Mosses.

    • Reproductive strategies include both sexual and asexual reproduction, with gemmae contributing to asexual methods.

Ecological and Human Relevance of Bryophytes

• Peat Moss (Sphagnum):

  • Holds up to 20 times its weight in water, making it valuable for horticultural uses.

  • Utilized in hydroponic gardening, surgical dressings, and soil conditioning.

  • Sphagnum harvesting occurs sustainably every 3 years, with 300,000 bales produced annually in specific regions.

• Human and Ecological Impact:

  • Bryophytes act as pioneer species in primary succession, help indicate water quality, and their biomass has various uses in gardening and pharmaceuticals.

Summary Comparison of Bryophyte Phyla

Conclusion

• Bryophytes play crucial roles in their ecosystems while offering significant benefits for human use, highlighting their ecological and economic importance.