Equisetum - Overview
Equisetum, commonly known as horsetail, is a genus of vascular plants that thrives in damp habitats. Renowned as a living fossil, it has existed since the Devonian period, making it an intriguing subject in plant taxonomy and evolution. This in-depth guide will help you master all the essentials of Equisetum for NEET Biology and beyond.
Introduction to Equisetum
Equisetum is the sole surviving genus of the family Equisetaceae. It is often referred to as a “living fossil” because it represents the last remnant of a large group of plants (the Equisetopsida) that dominated the Earth’s forests millions of years ago.
Common Names- Horsetail, Scouring rush, Snake grass
Habitat- Damp places, marshy areas, stream banks
Period of Origin- Devonian Period (around 400 million years ago)
Classification & Taxonomic Position
Kingdom - Plantae
Division - Pteridophyta (Some references group it under Polypodiophyta)
Class - Equisetopsida
Order- Equisetales
Family- Equisetaceae
Genus- Equisetum
Morphology & Key Characteristics
Rhizome
Underground, extensively branched.
Stores nutrients and anchors the plant.
Aerial Shoots
Typically hollow and jointed stems with distinct nodes.
A whorl of small, scale-like leaves surrounds each node.
Ridges and furrows present, containing silica, which gives the stem a gritty texture.
Branches
Lateral branches often arise in whorls.
Serve in photosynthesis, as the main stem is responsible for limited photosynthesis.
Leaves
Reduced to small scales around each node.
Non-photosynthetic; the stems and branches carry out most of the photosynthesis.
Sporangiophores
Specialised structures bearing sporangia (spore-containing sacs).
Arranged in cone-like strobili at the apex of reproductive shoots.
Life Cycle of Equisetum
Equisetum showcases a haplodiplontic life cycle typical of Pteridophytes, with alternation of generations between the sporophytic (diploid) and gametophytic (haploid) phases.
Sporophyte (Dominant Phase)
Diploid stage, which is the most conspicuous, long-lived phase.
Produces spores through meiosis in sporangia housed on sporangiophores.
Spore Dispersal
Each spore is equipped with elaters (band-like structures) that help in dispersal.
Spores are released when the cone dries out.
Gametophyte (Prothallus)
Haploid stage, small, photosynthetic, and short-lived.
Produces male (antheridia) and female (archegonia) reproductive organs.
Fertilisation
Requires water for the male gametes (antherozoids) to swim to the female gametes (eggs) in the archegonia.
Results in a diploid zygote.
New Sporophyte Formation
The zygote develops into the young sporophyte, continuing the cycle.
Reproduction in Equisetum
Vegetative Reproduction
Occurs through rhizomes.
Buds on the underground rhizome can sprout new shoots.
Asexual Reproduction
Takes place by fragmentation of rhizomes.
Common in stable habitats.
Sexual Reproduction
Involves production of spores by the sporophyte, leading to gametophytes.
Requires external water for fertilisation—typical of seedless vascular plants.
Economic & Ecological Importance
Ecological
Aids in soil stabilisation near waterways and marshy regions.
Offers habitat and shelter for microorganisms and small aquatic fauna.
Medicinal
Stems contain silica and have been used traditionally as a diuretic.
Research continues on potential antimicrobial properties.
Industrial
Historically, dried Equisetum (horsetails) served as a scouring material due to its abrasive nature.
Essential Study Materials for NEET UG Success
FAQs on Equisetum - A Comprehensive Guide for NEET
1. Why is Equisetum referred to as a “living fossil”?
Equisetum is called a “living fossil” because it is the only surviving genus of a once-dominant group of plants (Equisetopsida) dating back to the Devonian period. It has undergone minimal evolutionary change over millions of years.
2. Which habitat does Equisetum prefer?
Equisetum typically grows in damp and marshy areas, near stream banks and wetlands. It thrives where there is ample moisture for its reproductive processes.
3. How does Equisetum differ from typical ferns?
While both are pteridophytes, Equisetum has jointed, hollow stems with silica deposits and greatly reduced leaves. Ferns generally have broad fronds and no silica in their tissues.
4. Which part of Equisetum is primarily responsible for photosynthesis?
The green, hollow stems and lateral branches handle most of the photosynthesis, as the leaves are reduced to small, non-photosynthetic scales.
5. What is the role of silica in Equisetum stems?
Silica imparts a gritty texture, offering the plant structural support and protection. Historically, this abrasive quality made Equisetum useful for scouring and cleaning.
6. How are spores of Equisetum dispersed?
Equisetum spores have elaters—band-like structures that coil and uncoil in response to humidity changes, aiding in efficient spore dispersal when the cone (strobilus) dries out.
7. Does Equisetum require water for fertilisation?
Yes. As a pteridophyte, Equisetum depends on external water to allow male gametes (antherozoids) to swim toward female gametes (eggs) in the archegonia.
8. Can Equisetum reproduce vegetatively?
Absolutely. Vegetative reproduction occurs through the extensive rhizome system, where buds can give rise to new shoots even if spores fail to germinate.
9. What makes the Equisetum life cycle haplodiplontic?
Like all pteridophytes, Equisetum exhibits alternation of generations with a haploid gametophyte phase and a diploid sporophyte phase, both of which are free-living at different stages.
10. Why is Equisetum crucial for NEET Biology?
Equisetum illustrates key concepts such as vascular plant evolution, alternation of generations, and unique morphological adaptations—all of which are commonly tested in NEET UG.
