Liverworts: The liverworts grow usually in moist, shady habitats such as banks of streams, marshy ground, damp soil, bark of trees and deep in the woods. The plant body of a liverwort is thalloid, e.g., Marchantia. The thallus is dorsiventral and closely appressed to the substrate. The leafy members have tiny leaf-like appendages in two rows on the stem-like structures.

Characteristic Features of Liverworts

• The plant body of a liverwort is called a thalloid, which is dorsoventral in nature.
• The leaves of liverworts are arranged in rows (typically three rows) and tend to appear flattened. Both their thalloid and leafy forms often have an endosymbiotic relationship with fungi.
• The leaves are commonly lobed or divided. Sometimes, the lobe margins can also be toothed or ciliated.
• Rhizoids are thin-walled, unicellular, and usually hyaline.
• They are distinguished from other embryophytes by the presence of oil bodies, a unique membrane-bound organelle.
• The sporophyte setae of liverworts are parenchymatous. These parenchymatous cells elongate by expansion instead of cell division.
• Their capsules lack cuticles, columella and stomates that are usually common in hornworts and mosses.

Life Cycle of Liverworts

Liverworts can be monoicous or dioicous. Also, they show both sexual and asexual reproduction.

Asexual Reproduction

In liverworts, asexual reproduction takes place by fragmentation of the thallus, or by the generation of special structures called gemmae. These gemmae are multicellular, green, asexual buds that develop in the gemma cups, which are small receptacles present on the plant body or thallus. These structures become disconnected from the parent plant body and then germinate into new individuals.

Sexual Reproduction

Spore Germination – Typically, spore germination is initiated with swelling and division of the spore to form a multicellular protonema. The protonema is a highly branched thread-like structure in mosses, whereas it is reduced as cells in most hornworts and liverworts. The protonema develops into a mature gamete-bearing plant.

In sexual reproduction, the female and male sex organs are produced either on the same or different thalli. Here, the sporophyte is evolved into seta, capsule and foot. Usually the spores are produced inside the capsule, after meiosis. These spores germinate to form a free-living gametophyte.

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By Team Learning Mantras