Funaria is a moss with about 210 species known, 18 from India. It is commonly known as ‘cord moss’. The word Funaria was taken from the Latin word ‘Funis’, meaning rope. It is a cosmopolitan bryophyte that is found in both tropical and temperate regions of the world. It grows well in moist and shady places. It grows densely in patches of bright green colour. It can be found living on river banks, moist walls, rock crevices, humid soils and tree trunks.
Table of Contents
- Classification of Funaria
- External Morphology
- Reproduction in Funaria
- Sporophyte
- Frequently Asked Questions
Classification of Funaria
|
Kingdom |
Plantae |
|
Division |
Bryophyta |
|
Class |
Bryopsida |
|
Order |
Funariales |
|
Family |
Funariaceae |
|
Genus |
Funaria |
Common Indian species include: Funaria hygrometrica, Funaria fascicularis, Funaria obtusa
External Morphology
- Funaria is divided into two stages: leafy gametophyte and sporophyte.
- The gametophyte is the main plant body that is represented by a juvenile and an adult stage.
- The haploid plant body is divided into stem, leaves and rhizoids.
- The stem is erect, branched, green and photosynthetic. The branches arise from the lower portion of the stem.
- The leaves are arranged spirally on the stem. They are scattered towards the base and crowded at the apex. They are sessile and almost ovate in shape and have a distinct midrib.
- The stem is fixated on the substratum by rhizoids. They are branched, multicellular and appear like root hairs.
- The gametophytic plants are monoecious and homothallic. The male reproductive organ or antheridium and the female reproductive organs or the archegonium are borne on different branches of the same plant.
- Both the antheridium and archegonium are produced in clusters at the end of antheridial and archegonial branches, respectively.
- The sporophyte is attached to the archegonium in parasitic nature and is divided into a foot, seta and capsule.
Reproduction in Funaria
Funaria reproduces by both vegetative and sexual methods.
Vegetative Reproduction
- By Primary Protonema: The spores germinate to produce branched, filamentous and multicellular structures called primary protonema. These cells break into fragments to produce new protonemal cells which develop into a leafy gametophore.
- By Secondary Protonema: A protonema that is developed from any other means than the germination of spores is called secondary protonema. It is developed from broken or injured rhizoids, stems or leaves. It can give rise to a whole new gametophore.
- By Bulbils: Bulbils are small resting buds that arise from the rhizoids. They start dividing in favourable conditions and produce filamentous protonema that can grow into leafy gametophytes.
- By Gemmae: In unfavourable conditions, the terminal cells of the protonema divide transversely and longitudinally to give rise to 10-30 celled green bodies called gemmae. These structures start to divide and form new plants in favourable conditions.
- Apospory: Apospory is the development of gametophyte from sporophyte without spore formation. Vegetative cells of the sporophyte give rise to green protonemal fragments which later become a gametophyte. The gametophyte produced from apospory is diploid that gives rise to tetraploid and sterile sporophytes.
Sexual Reproduction
In Funaria, sexual reproduction is of oogamous type. The male reproductive structure is antheridium and the female reproductive structure is archegonium. The plant is monoecious (both male and female reproductive organs on the same plant) and autoicous (male and female reproductive organs grow on different branches of the same plant).
The main shoot of the gametophyte bears the antheridium in clusters and acts as the male branch. The female branches arise as lateral outgrowth from the base of the male branches and bears archegonia. The female branch grows higher than the male branch. Funaria is protandrous, meaning, the anther matures before the archegonia to promote cross pollination.
Refer: Difference between Cross Pollination and Self Pollination
Antheridium
The male sex organ is called antheridium. The antheridial branch is about 1cm in height. The branch bears reddish-brown to orange antheridium in different stages of development. The antheridia are surrounded by a rosette of leaves called perigonial leaves. The antheridial cluster, along with the leaf rosette, is known as the perigonium.
Numerous club-shaped, sterile and hair-like structures are found in the antheridia that are known as paraphyses. They store water, help in photosynthesis of dehiscence of antheridia and also protect the growing male reproductive organs.
Structure: The antheridium is a club shaped structure that has a short and stout multicellular stalk. The antheridial body is massive and elongated. It is covered by a layer of sterile cells called antheridial wall or jacket. The apex of the antheridium has a few layered thick walls called opercular cells. The androcyte mother cells are present below the wall layer. The androcyte mother cell divides to form two androcytes which further gives rise to biflagellated and elongated sperm or spermatozoid.
At maturity, the opercular cells absorb water and swell up. The walls of the opercular cells and androcytes get gelatinised and a terminal pore is developed at the tip of the antheridium. The androcytes are released from this pore covered in mucilage. The mucilage is dissolved in water and androcytes develop into biflagellated sperms.
Archegonium
The female sex organ is called archegonium. The female branch is borne higher than the male branch. Archegonium is borne in clusters at the tip of the archegonial branch.
Structure: The archegonium is a flask shaped structure. It consists of a neck, a swollen venter and a narrow neck. It is attached to the female branch by a stalk. The venter consists of a venter cavity surrounded by a double layered venter wall. The venter cavity contains a ventral canal cell and an egg. The neck consists of an axial row of 8-12 neck canal cells. The tip of the neck is closed by four cover cells.
On maturity, the neck canal cells and ventral canal cells disorganise to form a mucilage. The cover cell of the archegonium separates forming an open passage leading to the canal.
Fertilisation
The spermatozoids reach the archegonium by pollination by wind or splashing raindrops. The mucilage present at the mouth of the archegonia attracts the spermatozoids towards them. The spermatozoids then enter the venter cavity through the neck canal. One spermatozoid fuses with the egg cell to form a zygote which later develops into a sporophyte.
Sporophyte
Sporophyte is the diploid plant of Funaria. It is attached to the gametophyte like a parasite. The zygote undergoes repeated division to form a globular proembryo. The proembryo then develops into a diploid sporophyte. The sporophyte is attached to the tip of the female branch. The sporophyte is dependent on the gametophyte partially for nutrition.
The sporophyte can be divided into three parts:
- Foot: It is the swollen basal part of the sporophyte. It remains embedded in the convex tip of the female branch. It is composed of the parenchymal cells. The foot is the portion that attaches the sporophyte to the gametophyte. It helps in absorbing nourishment from the gametophyte.
- Seta: It is a long reddish-brown cylindrical structure. It connects the capsule to the foot. It is composed of an outer epidermis, a middle cortex and a central cylinder. The cortex is made up of thick walled cells and the central cylinder is made up of elongated thin-walled cells. It functions to carry food and water from the foot to the capsule.
- Capsule: The capsule is the body of the sporophyte where spores are developed. It is green, yellow or orange in colour and is pear shaped. It is the fertile region of sporophyte and consists of three parts:
- Apophysis: It is the basal sterile part of the capsule that is in direct contact with the seta. It is made up of an outer epidermis which bears stomata for gaseous exchange. The middle portion is the cortex which is made up of spongy parenchyma cells that contain chloroplasts and are photosynthetic in nature. The central cylinder is composed of elongated thin walled cells that conducts food and water from the seta to the theca.
- Theca: Theca is the middle portion of the capsule. It is made of a central sterile core called columella. The columella is surrounded by a spore sac. The spore sac contains spore mother cells which undergo meiosis to produce a tetrad of spores.
- Lid: The lid or the operculum is the sterile terminal portion of the capsule. The outermost layer is the epidermis that is thick walled while the inner layers are thin walled and parenchymatous. The lid is separated from the theca by a narrow circular constriction. Just above the constriction is a ring of 5-6 thin walled cells called annulus. Below the wall of the lid is a two ringed structure of peristome teeth. The outer ring of the peristome is exostome and the inner ring is known as endostome. They take part in the dehiscence of the capsule.
Dehiscence of the Capsule
As the capsule matures, the operculum is thrown off by the rupture of annulus, exposing the peristome teeth to the air. The capsule dries slowly and the peristome teeth ruptures. The peristome teeth form a fringe around the mouth of the spore sac, thus releasing the spores in small amounts.
Germination of Spores
The spores produced by sporophytes are called meiospores. The haploid spores are produced in the capsule by reductional division. The spore consists of an outer layer called exine and an inner layer called intine. The spore absorbs moisture and swells up, rupturing the exine. The intine first grows into a germ tube and later into a branched filamentous structure called protonema. The protonome grows on the substratum by fixing itself with rhizoids. Many lateral buds are produced from the grown protonema which gives rise to gametophytes.
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Also Read:
- Difference between Riccia and Marchantia
- Difference between Sporophyte and Gametophyte
- Moss: Characteristics, Life Cycle and Uses
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