Characteristics, life cycle (mosses, liverworts)

1. Introduction

1. Bryophytes are the simplest land plants and are often called “Amphibians of the Plant Kingdom” because they require water for reproduction.
2. They are non-vascular plants and lack true roots, stems, and leaves.
3. Commonly found in damp, shady places, such as moist soil, rocks, and tree trunks.
4. They reproduce through spores rather than seeds.
5. The dominant phase of their life cycle is the haploid gametophyte.

2. Characteristics of Bryophytes

1. Lack vascular tissues like xylem and phloem.
2. Possess rhizoids instead of true roots for attachment and water absorption.
3. Exhibit alternation of generations with dominant gametophyte and dependent sporophyte.
4. Water is essential for fertilization as sperm must swim to the egg.
5. Reproduce by fragmentation (vegetative) and spores (asexual).
6. Play a crucial role in soil formation, moisture retention, and ecosystem balance.

3. Classification of Bryophytes

1. Bryophytes are classified into two major groups:

3.1 Liverworts (Hepaticopsida)

1. Thalloid or leafy, lobed, and closely attached to the substrate.
2. Reproduce asexually through gemmae cups and sexually through spores.
3. Sporophyte consists of a foot, seta, and capsule.
4. Examples: Marchantia, Riccia.

3.2 Mosses (Bryopsida)

1. Most developed group of bryophytes.
2. Have two stages: Protonema stage (filamentous) and Gametophyte stage (leafy stage).
3. Absorb water and nutrients through rhizoids.
4. Examples: Funaria, Polytrichum, Sphagnum.

4. Life Cycle of Bryophytes

1. Exhibit alternation of generations between haploid gametophyte and diploid sporophyte.

4.1 Gametophyte Stage

1. Dominant and independent stage in the life cycle.
2. Produces male (antheridia) and female (archegonia) reproductive organs.
3. Antheridia produce motile sperm, which require water for movement.
4. Archegonia produce eggs, which are fertilized by sperm to form a zygote.

4.2 Sporophyte Stage

1. Diploid and dependent on the gametophyte.
2. Develops from the fertilized egg (zygote) inside the archegonium.
3. Consists of three parts: Foot (absorbs nutrients), Seta (stalk), and Capsule (contains spores).
4. Capsule undergoes meiosis to produce haploid spores, which disperse to form new gametophytes.

5. Economic and Ecological Importance of Bryophytes

5.1 Ecological Importance

1. Help in soil formation and prevent erosion by binding soil particles.
2. Contribute to water retention and improve soil moisture.
3. Act as pioneer species in barren and rocky areas.

5.2 Economic Importance

1. Sphagnum moss is used as a water-retaining material in gardening.
2. Used as packing material for fragile objects due to high moisture absorption.
3. Some bryophytes have medicinal properties and are used in traditional medicine.

6. Comparison of Liverworts and Mosses

7. Conclusion

1. Bryophytes are simple, non-vascular land plants that thrive in moist environments.
2. They show alternation of generations with a dominant gametophyte stage.
3. Play a crucial role in soil conservation, ecological succession, and moisture retention.
4. Have economic value in horticulture and traditional medicine.