A protonema (plural: protonemata) is a thread-like chain of cells that forms the earliest stage (the haploid phase) of the life cycle of mosses and liverworts. When a moss first grows from the spore, it grows as a protonema which develops into a leafy gametophore.
Moss spores germinate to form an algae-like filamentous structure called the protonema. It represents the juvenile gametophyte. While the protonema is growing by apical cell division, at some stage, under the influence of the phytohormone cytokinin, buds are induced which grow by three-faced apical cells. These give rise to gametophores, stems and leaf like structures (bryophytes do not have true leaves (megaphyll). These gametophores are the adult form of the gametophyte. Protonema are characteristic of all mosses and some liverworts but are absent from hornworts. Credits: Saksham R.T.
Rajtilak told , "Protonemata of mosses are composed of two cell types: chloronemata, which form upon germination, and caulonemata, which later dÀ aifferentiate from chloronemata.a Credits : Saksham R.T. 'Wr " The protonema stage develops directly from a spore
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- P.J. Davies (2013). Plant Hormones: Physiology, Biochemistry and Molecular Biology. Springer Science & Business Media. pp. 460–. ISBN 978-94-011-0473-9.
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