In this article we will discuss about the vegetative and sexual methods of reproduction in bryophytes. Bryophytes posses a characteristic feature and that is their tendency towards extensive vegetative reproduction. The vegetative reproduction takes place in favourable season for vegetative growth. Majority of the Bryophytes propagate vegetatively and it is brought about in many ways. In
Bryophytes asexual reproduction definition the growing point is situated at the tip of the thallus.
The basal, posterior or older portion of the thallus starts rotting or disintegrating due to ageing or drought. When this process of disintegration or decay reaches up to the place of dichotomy, the lobes of the thallus get separated. These detached lobes or fragments develop into independent plants by apical growth. This is the most common method of vegetative reproduction in Riccia, Marchantia, Anthoceros Bryophytes asexual reproduction definition some mosses like Sphagnum Fig.
Due to prolonged dry or summer or towards the end of growing season the whole thallus in some Bryophytes e. Later, it deep into the soil and becomes thick.
Under favourable conditions it develops into a new thallus. Tubers are formed in those species which are exposed to dessication drying effect of the air. Towards the end of the growing season, the subterranean branches get swollen at their tips to from the underground tubers. On the periphery of a tuber are two to three layers of water proof corky, hyaline cells develop. These layers surround the inner cells which contain starch, oil globules and albuminous layers. During the unfavorable conditions the thallus dies out but the dormant tubers remain unaffected.
On the return of the favourable conditions each tuber germinates to form a new plant e. Thus, tubers also serve as organ of perennation Fig. Gemmae are green, multicellular reproductive bodies of various shapes. These are produced in gemma cups, on the surface of the leaves, on stem apex or even inside the cells.
They get detached from the parent plant and after falling on a suitable substratum gemmae give rise to a new individual directly e. Multicellular gemmae produced along the margins of the dorsal surface of the thallus Bryophytes asexual reproduction definition. The adventitious branches develop from the ventral surface the thallus e. On being detached from the parent plant these branches develop into new thalli. In Marchantia, Dumortiera these branches develop from archegoniophore while in Pellia these branches arise from the dorsal surface or margins of the thallus Fig.
The liverworts possess an amazing power of regeneration. Part of the plant or any living cell of the thallus "Bryophytes asexual reproduction definition." In Sphagnum one of the branches in the apical cluster instead of forming drooping branches or divergent branches, develop more vigorously than the others and continues the growth upwards. This long upright branch has all the characteristics of main axis.
It is called innovation. Due to progressive death and decay of the parent plant these innovation become separated from the Bryophytes asexual reproduction definition plant and establish themselves as parent plants. Primary protonema is the filament like stage produced by the developing spores of the mosses.
It produces the leafy gametophores. It breaks into short filament of cells by the death of cells at intervals. Each detached fragment grows into a new protonema which bears a crown of leafy gametophores e.
The protonema formed by other methods than from the germination of spores is called secondary protonema. It may develop from any living cells of the leafy gainetophore i. From this arise the leafy gametophores or lateral buds in the same manner as in primary protonema e.
These small resting buds develop on rhizoids. Bulbils are devoid of chlorophyll but full of starch.
On germination bulbils produce a protonema which bears leafy gametophores Fig. The production of diploid gametophyte from the unspecialized sporophyte without meiosis is known as apospory e. In Funaria green protonemal filaments may arise from the unspecialized cells of the various parts of sporogonium. These protonemal filaments bear lateral buds which develop into leafy gametophores.
These are the small or broad detachable branches which help in vegetative reproduction. These are of two types: Arising from the individual cell of the leaf e. These cladia arise from the stem and occupy the same position as sexual branches e.
A number of catkins like deciduous branches develop over the entire surface of the gametophytic plant.
On separation these branches develop into new plant e. The apical part of the young rhizoids divide and re-divide to form a gemma like mass of cells e. These cells contain chloroplast and are capable to develop into new thallus. Fellncr, ; Campbell, Perennation is the survival from season to season, generally with a period of reduced activity between each season.
The spore and gemmae can also perennate and in some, instances even the protonema does. The perennial mosses perennate as gametophytes. Male and female sex organs are known as antheridia Sing, antheridium and archegonia Sing, archegoniumrespectively. Antheridium is stalked, pear shaped or oblong and has an outer one cell thick jacket which encloses a mass of fertile cells called androcytes. Each androcyte metamorphoses into biflagellate antherozoid.
Archegonium is stalked, flask shaped structure. It has a basal swollen portion called venter and an elongated neck. The neck is filled with many neck canal cells whereas venter has a large egg cell and a small venter canal cell. Antherozoids are attracted towards the neck of the archegonium chemotactically by certain substances like sugars, malic proteins, inorganic salts of potassium etc. The fertilized egg "Bryophytes asexual reproduction definition" zygote is the beginning of the sporophytic phase.
Il is retained within the venter of the archegonium. Without resting period, the zygote undergoes repeated divisions to form a multicellular structure called the embryo.
The first division of the zygote is always transverse and the outer cell develops into embryo. Such an embryogeny is called exoscopic. The sporophyte is usually differentiated into foot, seta and capsule. In certain cases it is represented only by capsule e. Sporophyte is attached to parent gametophytic plant body throughout its life.
It partially or completely depends on it for nutrition. Foot is basal, bulbous structure. It is embedded in the tissue of parent gametophyte. Its main function is to absorb the food material from the parent gametophyte. Seta is present between the foot and capsule. It elongates and pushes the capsule through protective layers. It also conducts the food to the capsule absorbed by foot.
Capsule Bryophytes asexual reproduction definition sporogenous tissue which develops entirely into spore mother cells it e. Spore mother cells divide diagonally to produce asexually four haploid spores which are arranged in tetrahedral tetrads. Elater mother cells develop into elaters e.
Elaters are present in liverworts and absent in mosses. Venter wall enlarges with the developing sporogonium and forms a protective multicellular layer called calyptra gametophytic tissue enclosing the sporophyte.
Each spore is unicellular, haploid and germinates into young gametophytic plant e. BotanyBryophytesReproduction in Bryophytes. Distribution, Habitat and Affinities Botany. Economic Importance of Bryophytes Botany.
This is a question and answer forum for students, teachers and general visitors for exchanging articles, answers and notes. Answer Now and help others.
Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted up and rise to the top. Vegetative reproduction involves no mixing of genes from two parents. Vegetative reproduction is known from bryophytes where sexual reproduction . Different writers may have slightly different definitions for a given term. Like all bryophytes mosses, have two forms of reproduction, Asexual Bryophytes asexual reproduction definition vegetative At regular intervals depending on species and weather condition, mosses.
most moss species exhibit clearly defined annual cycles of. Most bryophytes are capable of asexual reproduction, whether or not they.
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