Notes on Equisetum Systematic Position, Morphology, Gametophyte and Life Cycle

Systematic Position
Division: Sphenophyta
Class: Calamopsida
Family: Equisitaceae
Genus: Equisetum (Horse tails, Scouring rushes) Only living member

Species: Common species include E. arvense (road side), E. debile (river side)Habitat: grows in swampy soil along river side or sandy road sides
Habit: Bushy, perennial herbs
Equisetum: Plant body
Equisetum Plant body

  •     Sporophytic plant body
  •       Differentiated into root, stem and leaves
  •      Creeping or erect plant body
  •      Stem: consist of underground rhizome and upright green aerial branches.
  •       Jointed stem with nodes and internodes, internodes with longitudinal ridges and furrows and hollow interior
  •      Silica deposits in stem make it rough (Scouring rushes)
  •        Leaves: nodes with small, sessile microphyllous scale leaves in whorls
  •        Function: photosynthesis
  •      Fertile branches bear strobili after some vegetative growth
  •        Roots: Adventitious roots arise from the nodes of rhizome
  •      Other features: Homosporous nature, Eusporangiate
Equisetum Stem Anatomy T.S
     Vegetative Reproduction:  Fragmentation of rhizome, Tubers formed on rhizome
Strobilus or structure of cone

  •  Equisetum is homosporous and Eusporangiate
  •   Strobili are borne terminally and singly on aerial fertile branches.
  • Strobilus consists of a central axis on which stalked sporangiophores with sporangium are arranged in whorls
·         Umbrella shaped structure with a slender stalk and a hexagonal peltate disc
·         The underside of peltate disc bears variable number of sac like sporangia
·         The number of sporangia in each sporangiophore may vary from 5-10
·         Sporangium consists of a 2 cell thick wall, with large number of homosporous spores.  Dehiscence along longitudinal slit. Spores are dispersed by  wind with the help of elaters
Spores and Elators
          Spores are Green, large, uninucleate, spherical, chloroplast containing structures with exine, intine and outermost epispore
          Elaters are spirally coiled , spoon shaped hygroscopic structures formed from epispore of haploid spore
          Each spore has 4 spirally arranged hygroscopic elaters
          Function: helps in dehiscence of sporangium and spore dispersal
Gametophyte or prothallus of Equisetum
Gametophyte or prothallus of Equisetum

  •     Spores falling on suitable substratum germinate to form green prothallus with rhizoids for fixation.
  •      Prothallus consists of a basal disc and number of green vertical lobes.
  •       Monoecious or bisexual: both antheridia and archegonia are present.
  •      Antheridia may occur on vertical lobes or basal disc embedded.
  •       Antheridium produces 256-512multiflagellate, spirally coiled spermatozoids.
  •      Archegonia flask shaped structures at the base of vertical lobes.
  •       Fusion forms embryo which give rise to new plant.
     Life cycle: Homomorphic alternation of generation
Life cycle of Equisetum
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