INTRODUCTION
The term “Bryophyta” was proposed by “Robert Braun” The study of Bryophytes is known as Bryology.
Hedwing is considered to be the father of Bryology. But according to some scientist it is believed that Cavers is the father of Bryology.
Father of Indian Bryology is Prof. Shiv Ram Kashyap
General characteriltics:
Bryophytes are the first land plant. It is believed that, they originated from aquatic plant and they come on land through water. Because some bryophytes have characters similar to aquatic plants (eg. presence of air canal)
Bryophtes are known as amphibians of the plant kingdom, because they need water to complete their life cycle. Mostly bryophytes are found on land.
Bryophytes are not considered as the successful land plants because vascular tissue is absent and they nead water for fertilization. Due to the absence of vascular tissue bryophytes can not grow very tall. The process of water conduction in bryophytes takes place with the help of parenchyma. Parenchyma is a living tissue.
Roots are absent in bryophytes. Stem and leaves of bryophytes are functionally similar to the stem and leaves of higher plants.
Bryophytes are sciophytes, i.e. bryophytes prefer to grow in moist (wet) and shady places.
Life cycle of Bryophytes :
1. The plant in bryophyte is gametophyte. It is haploid.
2. Sex organs are formed on gametophyte. Sex organs are multicellular and jacketed in bryophytes. Male sex organs are called as antheriudium and female sex organs are called as archegonium.
3. The male gametes of bryophytes are motile. These motile male gametes are called as antherozoids, Antherozoites are comma shaped and biflagellate. Female gamete is called egg.
4. In Bryophyta, fertilization is done by zoodiogamy i.e. male gamete reaches the female gametes and fertilizes it.
5. As a result of fertilization, a diploid zygote is formed. This zygote initiates the sporophytic generation. Sporophytic generation is a diploid stage.
6. Zygote is developed by mitosis and formes sporphyte, which is known as sporogonium or embryo (2N)
7. During the development first division is transverse in zygote and second division is vertical. Third division is also vertical but at right angle to second division, therefore an eight called embryo is formed.
Now a periclinal division takes place in every cells of eight called embryo. As a result of it a 16 called
embryo is formed. Now these sixteen cells are arranged in two layers.
(i) Outer 8 cells - Called Amphithecium
(ii) Inner 8 cells - Called Endothecium
8. Now cells of endothecium divided and form many cells which are known as sporogenous cells. Some sporogenous cells become sterile and called nurse cells.
Remaining sporogenous cells function as spore mother cells. Now meiosis takes place in spore mother cells, result of it haploid spores are formed. Nurse cells provide nutrition to spores mother cells.
9. The germination of spores is direct or indirect. In Liverwort & Hornworts the germination of spore is direct i.e. each spore forms a gametophyte after germination i.e. each spore forms one thallus.
But the germination of spores in Mosses in indirect. In mosses a multicellular filament in formed after the germination of spore. This filament of known as protonema. Now buds are formed on every cells of protonema. Each bud develops and form a gametophyte plant. Indirect germination is best for survival. Mosses are gregarious in nature because they appear in group.
IMP NOTE :
Sexual reproduction in bryophytes in oogamous type and life cycle in halplodiplontic type.
In Bryophyta the sporophyte is depend on gametophyte This is a unique character of bryophyta.
HEPATICOPSIDA- LIVER WORTS
(i) All the bryophytes includes in this class have shape like liver so they are known as liverworts.
(ii) Plant body of this group is thallus like. Rhizoids and scales are present on thallus. Rhizoids are unicellular and unbranched. Scales are multicellular.
(iii) The sporophyte of Liverworts is completely depend on gametophyte i.e. it is depend on gametophyte for food, water and habitat.
(iv) The sprophyte of Liverwort is made up of foot, seta and capsule. (Except Riccia sprophyte is made up of only capsule).
(v) In this class formation of spores and nurse cells takes place by the cells of endothecium. Cells of emphithecium form only wall of sporophyte.
Amphithecium = Wall of sprophyte
Endothecium = sporogenous cells = spore mother cells + nurse cells
(vi) Elaters are present in sporophyte of some members of liverworts. (eg. Marchantia - In Marchantia nurse cells are modified in to elaters) Elaters are hygroscopic and they help in dispersal of spores.
Eg. of Liverworts – Riccia, Marchantia, Cryptothallus, Reilla, Pellia, Porella
Note : In Bryophytes, sporophyte of Riccia in the simplest.
ANTHOCEROPSIDA- HORNWORTS
(i) The plant body of this group is also thallus like. Scales are absent but rhizoids are present on thallus. Rhizoids are unicellular and unbrahcned.
(ii) The sprophyte of Hornworts is divided into foot and capsule.
(iii) The sporophyte of Hornworts is not completely depend on its gametophyte i.e. it is semiparasite because its sprophyte is photosynthetic therefore it can manufacture its own food. So it does not depend on gametophyte for food, It depends only for water and habitat.
(iv) In horn worts wall of sporophyte and spores are formed by cells of amphithecium. Cells of endotherium formed only elaters.
Amphithecium = Wall of sprophyte and spores
Endothecium = Elaters
(v) In hornworts spore forming cells and elaters forming cells are separate, so elaters are known as pseudoelaters. Pseudoelaters are structurally and functionally similar to true elaters.
(vi) In hornworts on the basal part of sprorophyte, a special type of meristem is present. Due to the activeness of this meristem, the sporophyte grows rapidly. It grows like the horn, of animals. eg. Notothylus, Anthoceros
Note : Anthoceros have some Algal like characters such as -
(i) Archegonia is jacketless
(ii) In each cell of Anthoceros, only one chloroplast is present which is a character of green algae. In the cells of higher plants, many chloroplast are present.
(iii) Pyrenoides (starch storing granules) are present in the chloroplast of Anthoceros, which in an algal character.
(iv) Anthoceros show ancestral characters i.e. bryophytes have originated from green algae.
Note : Due to these reasons class anthoceropsida also termed as synthetic archegoniatae.
BRYOPSIDA OR MUSCI- MOSSES
(i) All the Mosses are included in this class. The plant body of mosses is made up of stem, leaves and rhizoid. The Rhizoids present in the plants of this class are multicellular and branched. These rhizoid have oblique septa.
Note -
The presence of leaves in gametophyte is one of the unique character of Moss. In plant kingdom not a single gametophyte has leaves.
(ii) The sporaphyte of mass is brophyta is highly developed while the sprophyte of liverwort is the simples. The sporphyte of moss is divided into foot, seta, capsule.
(iii) The sporophyte of mosses is also semparasite like, hat of Hornworts. i.e. it is photosynthetic. The sporphyte absorbs the water from gametophyte with the help of foot.
(iv) Capsule is the fertile part of the sporophyte i.e. formation of spores takes place in it. Foot and seta are the sterile part of the sporophyte.
(v) Seta helps the capsule to remains in the air, due to which the dispersal of spores can take place conveniently.
(vi) In bryopsida cells of amphithecium form wall of sprophyte. Cells of endothecium form spores. Elaters and nurse cells are absent in bryopsida.
Ampithecium = Wall of sporophyte
Endothecium = Spores
Common examples of mosses are Funaria, Polytrichum and Sphagnum
Note :
(1) In Riccia, the sporophyte is made up of only capsule i.e. the whole sprophyte is fertile in it.
(2) During evolution there occur gradual sterilization of sporophyte i.e. gradual reduction of fertile part and gradual development of sterile part.
(3)Asexual reproduction in Marchntia takes places by fragmentation of thalli, or by the formation of specialized structures called gemmae (sing, gemma) Gemme are green, multicellular, asexual buds, which develop in small receptacles called gemma cups located on the thalli. The gemmae become detached from the parent body and germinate to form new individuals.