Selaginella is classified as a pteridophyte. Additionally, it is known as spikemoss or club moss. It is the family of Selaginellaceae’s largest and only extant genus. Spike mosses, or selaginella plants, are fascinating herbs that comprise one of the largest land plant genera. The fossil record indicates that Selaginella plants have existed over numerous epochs. Selaginella plants have an extraordinary life cycle that is quite unlike that of blooming plants. Selaginella is also known as the resurrection plant.’ It earns this moniker due to its ability to rehydrate following dehydration, most notably in desert forms such as Selaginella lepidophylla. Selaginella plant species number in excess of 700 worldwide. This adaptable and robust plant possesses a variety of intriguing characteristics.
Due to the arrangement of their branching and leaves, Selaginella plants frequently resemble ferns. They can grow as upright, branched plants or as creeping plants. Roots develop directly from the stems of creeping plants. Selaginella species have simple, scale-like leaves. Heterosporous plants produce a variety of spore types that result in unisexual gametophytes; thus, there is no possibility of intragametophytic selfing, and the spores/gametophytes can evolve toward specialization for their unisexual roles (e.g., female gametophytes can be produced from larger spores and can self-replicate).
They are vascular plants that do not produce seeds. They are primarily found in shaded places, however, certain species do occur in seasonally dry or xerophytic situations. They can be found on tree trunks, rocks, and forest floors, among other places.
Life Cycle of Selaginella-
As with other pteridophytes, Selaginella undergoes generational alternation. The life cycle is biphasic, with diploid sporophyte generation followed by haploid gametophyte generation. This is referred to as a haplo-diplontic life cycle.
The sporophyte stage of the life cycle is the most prominent. The primary plant body is a diploid sporophyte with genuine roots, stems, and leaves.
Selaginella is heterosporous, which means that it produces both microspores and megaspores. Spores are haploid and are formed in the spore mother cells via meiosis. Male and female gametophytes are formed when spores germinate. They are little but self-sustaining organisms that are multicellular and photosynthetic.
Male and female gametophytes, respectively, bear antheridia and archegonia. When male and female gametes fuse, a diploid zygote is formed, which grows into a well-differentiated sporophyte.
Male Gametophyte
Male gametophytes are formed when microspores germinate. When microsporangium reaches maturity, it dehisces and the spores are blown away by the wind. Microspores germinate in the microsporangia. Generally, the spores are discharged at the 13-cell stage, which comprises one prothallial cell, four androgonial cells, and eight jacket cells. Primary androgenetic cells divide and differentiate into antherozoids. Antherozoids are biflagellate organisms that swim in the direction of the archegonium.
Female Gametophyte
Megaspores of female gametophytes germinate to form female gametophytes. Female gametophytes develop within the megasporangium. Female gametophytes are liberated following fertilization or the creation of an archegonium. Following liberation, it binds to an appropriate substratum and forms rhizoids that aid in anchoring and water absorption.
Archegonium is a gametophyte that is embedded in gametophytic tissue.
Anterozoids swim and make a beeline for archegonium. Fertilization requires water. After fertilization, the nucleus of antherozoids and egg unite to form a diploid zygote or oospore. The oospore is the first generation of sporophytes. The oospore divides and creates a multicellular structure from which diverse tissues such as stem, root, cotyledons, and rhizophore differentiate.
In certain species, oospore development is completed in the megasporangium and does not fall to the ground until a seedling with primary roots has formed.
Morphology of Selaginella-
- It is an evergreen herb with numerous branches and a delicate appearance.
- Primary roots are transient in nature. At the rhizophore’s tips, adventitious roots are found.
- Rhizophores are leafless, colorless branches that grow downward from the prostrate stem. When rhizophores reach the soil, adventitious roots form at the tip.
- Green, dichotomously branched stem that is either erect or prostrate with erect branches.
- At the developing tip of the stem, a single apical cell is often present.
- The leaves are tiny and have a pointed tip. They are covered in scaly leaves.
- The midrib of the leaves is unbranched.
- The homophyllum subgenus contains similar spirally oriented leaves.
- The subgenus heterophyllum has two distinct leaf forms. Small leaves are found on the dorsal side of the stem, whereas larger leaves are found on the ventral side in pairs.
- Sporophylls, or spore-bearing leaves, are structurally identical to conventional leaves but are found in clusters called strobilli. They are typically found at the tips of branches and are covered in sporangia.
- Ligules are tiny outgrowths found near the base of the adaxial side of the leaf.
CONCLUSION-
Selaginella stellata, often known as starry spike moss or starry spike-moss, is a spike moss species in the Selaginellaceae family.
Selaginella species are mostly used as food, medicinal plants, handicrafts, and ornamentals. S. doederleinii is used as a bactericide in Chinese traditional medicine to treat cardiovascular disorders and cancers of the nose, throat, lung, and liver.