Give a brief account of the general characters of Bryophytes.
Q. Give a brief account of the general characters of Bryophytes.
Ans. The Bryophytes include the simplest and most primitive members of the embryophyta. This group includes about 860 genera and 25000 species. They occupy an in portant place in the plant kingdom although they have little economic value. They are cosmopolitan in distribution, mostly moist and shade loving but terrestrial. These plants occur in abundance in the temperate regions and are most common in rainy seasons. They usually grow in tufts or cushions and contribute much as a whole to the green colour of the mountains and forests.
With the exceptions of a few water forms, e.g. Riccia fluitans, Ricciocarpus, Riella. The Bryophytes are simplest and truly and inhabiting plants present on moist and shady places. They may be regarded as incompletely adopted to land conditions, because they require water for vegetative growth, fertilization and for other processes of life and hence are commonly called as “amphibians of plant kingdom”.
Occurrence :
(i) On moist walls, soil, logs and tree trunks.
(ii) Some may be lithophyte, epiphyte or aquatic.
(iii) Mostly the members of Hepaticae grow on hills.
(iv) Mostly the members of Musci occur on damp walls of plains in rainy reason or on hills.
Size and form :
The members of Bryophytes are smaller in size ranging from few millimeters to several centimeters. The largest known bryophyte Dawsonia, is nearly 40 to 50 cm. in height.
The plant body is thalloid and liverlike in the members of Hepaticae while it is small plant like having ‘leaf, ‘stem’ Rhizoids in the musci. The plants are mostly green in colour i.e. autotrophic in nutrition.
The plants represent the gametophytic generation and it after gametic fusion forms the sporophyte which is normally dependent on gametophyte.
The sporophyte after reduction division again forms the gametophyte. Thus
there is a distinct alternation of generation.
Characteristic Features:
1. They usually occur on moist and shady places.
2. The plant body is green in colour and is either thalloid in appearance (liver worts) or may have a differentiation of ‘leaf’, ‘stem’ and rhizoids (Musci).
3. The plant body is gametophyte.
4. Plants remain attached to the substratum by means of rhizoids, whose function is fixation and absorption. They may be unicellular or multicellular and smooth walled or tuberculated.
5. Internally the plant body does not show any vascular tissue like xylem or phloem.
6. The gametophytic plant body reproduces both by vegetative and sexual means.
7. The sexual reproduction is of oogamous type and takes place by definite male (Antheridium) and female (Archegonium) reproductive organs.
8. Antherozoids are motile, biciliated structure, produced in large numbers.
9. Archegonium is multicellular flask shaped organ having neck canal cells, ventral canal cell and an egg.
10. Water medium is essential for fertilization.
11. Fusion of antherozoid and eggs result in the formation of Zygote or Oospore which is diploid (sporophyte) in nature.
12. The oospore develops into the sporophyte which is usually differentiable into foot, seta and capsule.
13. Spores are formed in capsule after reduction division. All spores are alike.
14. Spores on germination give rise to the gametophytic plant body usually through protonema.
15. There is a distinct alternation of generation.
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