Objectives
Fern Plant
Kingdom: Plantae
Division: Filicinophyta
Habitats of Fern Plants
They grow mostly in moist habitat on land or trunks of trees and palm trees.
Examples of fern Plants
Fern plants include silver-back fern (Pityrogramma), Nephrolepis, Dryopteris.
Structure of Fern Plant
Fern has an underground stem called rhizome; thin adventitious roots, which absorb water and mineral salts and prominent leaves, called fronds. Fronds emerge from the rhizome as a coiled structure which gradually unrolls as growth proceeds. Each frond is pinnately compound, made up of several leaflets (pinnae). The leaf lamina is covered with shiny cuticle which reduce the rate transpiration.
Asexual reproductive structure (Sporangia, containing spores) develops on the under-surface of the mature leaflets. Cluster of sporangia called sori, are found at the leaflet margins. A protective structure called an indusium covers each sorus (plural: sori). The stem, roots and leaves have well developed vascular tissue.
Life cycle of Fern Plant
The spores develop in the sporangia, are released and dispersed when the sporangia burst on ripening. Under favorable condition of moisture and temperature, each spore germinates into a small, flat, heart-shaped photosynthetic structure called prothallus (i.e., the gametophyte). The prothallus is anchored to land by unicellular rhizoids. A matured prothallus bears the antheridia, the male sex organs and archegonia, the female sex organs on its under-surface. The antheridia produce bi-flagellate sperms called antherozoids. Each archegonium produces a single egg called oosphere. The sperm swims in a film of water on the surface of the prothallus to fuse with the egg to form a zygote. The zygote grows into an embryo and eventually develops into fern plant, the sporophytes. The gametophytes tissue decays and the sporophytes live independently.
The life cycle of the fern plant follows the pattern of alternation of generations. The gametophyte of the fern plant is small and insignificant compared to the sporophyte. Therefore, the sporophyte generation is dominant. The gametophyte and sporophyte are independent.
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