Generally referred to as the “amphibians of the plant kingdom”, Bryophytes are non-vascular terrestrial plants (lacking a true vascular system). These plants lack the right type of tissues for the development of true stems, roots or leaves.
The term Bryophyta comes from the word “Bryon” which means mosses and “Phyton” which means plants. These small plants inhabit damp and shady regions. They reproduce through spores. Bryophytes are amphibians of plants, these terrestrial plants need water to be able to complete their life cycle during sexual reproduction.
This division of the kingdom comprises Mosses, Hornworts and Liverworts. Bryophytes are the pioneers of land plants. The body of plants is thallus and is attached to the substratum by rhizoids that are multicellular or unicellular. It lacks vegetative structure and possesses leaf-like, stem-like, root-like structures.
These plants exhibit alternation of generation between independent gametophytes with sex structures that produce eggs and sperms. The dependent sporophytes have spores. The main plant body is a gametophyte that is a haploid.
This classification of green plants finds themselves between thallophytes and vascular cryptograms. They are the primitive and simplest group of Embryophyta. The very presence of swimming antherozoids is an indication of its aquatic ancestry. In these land-dwellers, the functions of roots are carried out by rhizoids.
Reproductive Structure in Bryophytes
The structures involved in reproduction are jacketed and multicellular, in algae, it is unicellular and non-jacketed. Archegonium is the female sex organ appearing for the first time in Bryophytes. Flagella are of the whiplash-type and sperms are biflagellates. In these, fertilization occurs in the presence of moisture or water. The fertilized egg continues to stay in the archegonia’s venter where it neither moves into the resting phase nor does it become independent of its parent gametophyte.
The zygote experiences repeated divisions, forming an undifferentiated multicellular structure referred to as the embryo. The first division of the zygote is transverse, the apex of the embryo develops from the outer cell and is exoscopic. Upon further differentiation and division, the embryo produces a comparatively small spore-producing structure – sporangium. Sporophytes produce spores that are non-motile, cutinized and wind-disseminated, referred to as meiospores. In them, a heterologous type of alternation of generation in their life cycle is seen.
Interesting Facts About Bryophytes
- Possibly, there are about 25,000 species of mosses and liverworts all over the world
- The smallest bryophyte is about 5 mm (Zoopsis). The tallest is about 50-70 cms (Dawsonia)
- Mosses and liverworts could be seen inhabiting all continents, even Antarctica
- Polytrichum, the moss is known to be the largest Bryophyte in Illinois, usually reaching about 10-15 cms in height. These are known to be associated with the tallest known moss, the New Zealand genus Dawsonia which could go up to 50 cm in height
- Several mosses possess leaves that are only one cell thick. It measures one-hundredth of a millimetre
Desert moss (Syntrichia caninervis) utilize barbed awns towards leaf terminals to trap moisture. These awns enable them to consume water from the rare rains, fog and mists
This was a synopsis on Bryophytes. Coming up next is a post on the Hardy Weinberg principle. For more such content, subscribe to BYJU’S YouTube Channel.