Liverworts and Their Classification

Liverworts

• Liverworts are non-vascular plants similar to mosses.
• They are primitive plants with no seeds, flowers, fruit, wood, or vascular tissue.
• Reproduce via spores and many species have only a single layer of cells.
• Lack stomata, structures used by most plants for photosynthesis.

Liverwort Classification

• Divided into two classes: Marchantiopsida and Jungermanniopsida.
• Marchantiopsida contains complex, thallose liverworts.
• Jungermanniopsida contains leafy liverworts.
• Simple thallose liverworts are found in both classes, but mainly in Jungermanniopsida.

Distinguishing Features Between Classes

• Marchantiopsida: Spore capsule wall has a single layer, spore mother cells are unlobed, and initial development of antheridia differs from Jungermanniopsida.
• Jungermanniopsida: Spore capsule wall has two or more layers (except for the genus Haplomitrium), spore mother cells are lobed, and initial antheridia development differs from Marchantiopsida.

Oil Bodies

• Found in about 90% of liverwort species, are distinct cell organelles containing terpenoid oils.
• Unlike oil droplets in other plants, are bounded by true membranes.
• Vary in size, shape, color, chemical composition, and cell distribution.
• Disappear in dried specimens and are best studied in fresh material.
• Functions remain debated, with potential roles in UV protection, cold resistance, and herbivore deterrence, but no conclusive evidence exists.

Reproduction

• Liverworts have two reproductive methods: asexual/vegetative and sexual.

Sexual Reproduction

• Similar to mosses, with sexual parts in antheridia (male) and archegonia (female) developing on separate plant bodies.
• Thallose liverworts differ, with antheridia and archegonia produced on umbrella-like structures in some species, or hidden in pockets on the leaves in others.
• Leafy liverworts produce mobile antherozoids (sperm) requiring water to reach archegonia for fertilization.
• After fertilization, a sporophyte develops attached to the parent plant.
• Thallose liverworts utilize raindrops to project sperm up to a meter away, targeting special cup-shaped splash areas on the leaf surface or dedicated structures.

Sporophyte Development

• Leafy liverworts elongate their delicate seta, carrying the capsule into the air.
• The capsule releases spores with hygroscopic elaters, splitting open and dispersing the spores for germination.
• Thallose liverworts have sporophytes hidden under structures or in pockets, with spores released directly.
• The gametophyte can reproduce vegetatively and produce gametes for saprophyte development.

Asexual Reproduction

• Occurs via older plant parts dying off and separating branches, specialized branches, or dropped leaves.
• Thallose liverworts have specialized structures called gamma cups producing numerous gametes released by water droplets splashing into the cup, spreading the gametes for growth.

Explore the fascinating world of liverworts, non-vascular plants similar to mosses. This quiz will test your knowledge on their distinguishing features, reproduction methods, and the classification into Marchantiopsida and Jungermanniopsida. Get ready to dive into the details of these primitive plants!