General characteristics of bryophytes
Term ‘Bryophyta’ is derived from Greek words; bryon = moss and phyton = plants. Braun (1864) for the first time used term 'Bryophyta'. Bryology is the study of Bryophytes.
Hedwig is called ‘Father of Bryology’ and Shiv Ram Kashyap (S R Kashyap) is the ‘Father of Indian Bryology’.
Bryophyta is division of primitive land plants, which includes non-vascular embryophytes. This groups included about 1000 genus and more than 25000 species. These plants have evolved on earth during Silurian period of Paleozoic era (about 395 – 430 million years ago).
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| Diverse forms in Bryophytes |
Plant body is small ranging between 2 to 60 cm in height. Dawsonia superba is the tallest self-supporting moss growing up to the height of 60 cm. This species is found in Australia, New Zealand and New Guiana.
They do not have any mechanical tissues, hence cannot grow tall.
They also lack true vascular tissues (xylem and phloem are absent). Rather they have some other tissues (leptoids and hydroids) for the conduction of water and nutrients. These tissues lack lignin.
They are land plants (terrestrial) but need water for sexual reproduction. Hence, they are called “Amphibians of plant kingdom”.
These plants lack mechanism to protect water losses (cuticle is absent). Hence, they grow in damp and shady places only.
They range from very delicate and simple thallus to well-differentiated plants.
Their lifecycle shows alternation of generation and gametophytic phase is the dominant phase.
Main plant body is haploid (n) gametophyte. The diploid (2n) sporophyte is semi-parasite on it.
The thalloid gametophytic plant body is differentiated in to rhizoids, axis (stem) and leaves.
Gametophyte produces multi-cellular and jacketed sex organs. Male sex organ is antheridia, whereas, female sex organ is archegonia.
Sexual reproduction is of oogamous type.
After fertilization, multi-cellular embryo (2n) develops inside archegonium.
Sporophytic phase is differentiated into foot, seta and capsule.
Meiosis takes place in the spore mother cells (sporic meiosis) inside the capsule and produces haploid spores of similar types (homosporous).
These haploid spores germinate into gametophytic thallus (in lower Bryophytes) or juvenile gametophyte called protonema (in higher Bryophytes).
There is progressive sterilization of sporogenous tissue noticed from lower to higher Bryophytes.
First published on 13-04-2021
Last updated on 01-05-2021
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