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ONE DAY TEACHERS WORKSHOP ON REVISED SYLLABUS OF BOTANY�B.Sc. I

SEMESTER I

BOTANY PAPER II: DSC-14A:

BIODIVERSITY OF ARCHEGONIATE-BRYOPHYTES, PTERIDOPHYTES, GYMNOSPERMS

WELCOME

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Resource Person

DR. LAVATE RAJENDRA ANANDA

M.Sc., M.Phil., Ph.D.

ASST. PROF AND HEAD

DEPARTMENT OF BOTANY

RAJE RAMRAO MAHAVIDYALAYA, JATH; DIST.-SANGLI

Email: bryoraj@gmail.com

Mob: 7588627653/9623420161

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UNIT 1: BRYOPHYTES

1.a: General Characters, Adaptaion to land Habit, Classification-as per G.M. Smith upto orders, Alternation of generation.
Economic Importance.
Morphology, anatomy and life cycle (excluding developmental stages) of following types
Heapaticopsida: Riccia
Bryopsida: Funaria

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BRYOPHYTES: Introduction

The term "bryophyte" comes from Greek root, “bryon" means “tree-moss, oyster-green" and “phyton” means "plant".
The study of bryophyte is called as ‘Bryology’.
Hedwig is called as ‘Father of Bryology’ and Shiv Ram Kashyap is known as ‘Father of Indian Bryology’.

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Bryophytes are an ancient and diverse group of nonvascular plants chlorophyllous, autotrophic, embryophytic, atracheophytic, archegoniate and amphibious cryptogams which show invariable heteromorphic alternation of generations in their haplodiplontic life cycle.
They include three main taxonomic groups: liverwort (Hepatophyta / Hepaticae/ Hepaticopsida / Marchantiophyta), hornworts (Anthocerotophyta / Anthocerotae/ Anthocerotopsida) and mosses (Musci / Bryophyta / Bryopsida) which have evolved quite separately.

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Most bryophytes have erect or creeping stems and tiny leaves, but hornworts and some liverworts have only a flat thallus and no leaves.
Bryophytes are members of inconspicuous and smaller in size (2cm to 60 cm) but some forms are large and grow upto the height of 60 to 90 cms.
They don’t attain great height because of absence of roots, vascular tissues, mechanical tissues and cuticle.
Worldwide there are about 900 genera and 25000 species out of which possibly 10,000 species of mosses, 7000 liverworts and 200 hornworts.

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They are cosmopolitan in distribution. Bryophytes are poorly recorded in ancient periods due to their delicate nature.
The fossil record shows that bryophytes evolved about 395-430 million years ago (i.e. during Silurian period of Palaeozoic era).
The liverworts and mosses were well represented in the carboniferous period. They are considered intermediate between the algae and the pteridophytes.

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Introduction

Bryophytes (nonvascular Plants) are the only embryophytes (plants that produce an embryo) whose life history includes a dominant gametophyte (haploid) stage.
They are an ancient and diverse group of non-vascular plants.
They comprise three main taxonomic groups: mosses (Bryophyta), liverworts (Marchantiophyta or Hepatophyta) and hornworts (Anthocerotophyta) which have evolved quite separately.

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They are not considered to have given rise to the vascular plants but they probably were the earliest land plants Like the rest of the land plants, they evolved from green algal ancestors, closely related to the Charophytes.
Most bryophytes have erect or creeping stems and tiny leaves, but hornworts and some liverworts have only a flat thallus and no leaves.
Worldwide there are possibly 10,000 species of mosses, 7000 liverworts and 200 hornworts.

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Bryophytes are terrestrial plants except few aquatic genera like Riccia fluitans and Ricciocarpos natans.
As they require water for the process of fertilization particularly for swimming of biflagellate antherozoids from antheridium up to the neck of archegonium they are called as “amphibians of plant kingdom”

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General Characters

Though they started land life, they require presence of water to complete their life cycle for movement of motile male gametes (antherozoids).
They are predominantly amphibious in nature, hence called “amphibians of the plant kingdom”

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Bryophytes are the simplest and the most primitive land plants. They are characterized by early development of embryo within the embryo sac.
Though they started land life, they require presence of water to complete their life cycle for movement of motile male gametes (antherozoids).
Bryophytes show “heteromorphic alternation of generations”. The gametophytic and sporophytic generations alternate with each other regularly in the life cycle. In this the haploid plant body is gametophyte and it is dominant phase. Diploid sporophyte is physically and nutritionally dependent on the gametophyte.

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Habitat

Bryophytes are primitive land plants that grow on moist shady places. They prefer moist, cool and shady places to grow.

Few of them grow in water and others in bogs, moist walls, rocks and tree trunks.

Riccia fluitans

Ricciocarpos nutans

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Plagiochasma appendiculatum �growing on moist walls along with mosses

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Plagiochasma intermedium and P. pterospermum�growing in the crevices of walls

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Targionia hypophylla�growing on moist soil crusts

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Leptolejeunea foliicola growing on leaves (Epiphyllous)

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Lejeunea flava �growing on rotting wood

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Mosses and Hornworts are also growing on different moist habitats

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Bryophytes form green carpet in the forest enhancing aesthetic value

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Bryophytes show “heteromorphic alternation of generations”. �The gametophytic and sporophytic generations alternate with each other regularly in the life cycle.�In this the haploid plant body is gametophyte and it is dominant phase. �Diploid sporophyte is physically and nutritionally dependent on the gametophyte.�Image: Fossombronia himalayensis�

Gametophyte

Sporophytes

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�

In primitive bryophytes the gametophyte is dorso-ventral, dichotomously branched green prostrate structure (Liverworts & Hornworts)�

In few advanced forms gametophyte is differentiated into stem, leaves and rhizoids (Mosses)

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Bryophytes are autophytes and lead autotrophic mode of nutrition�Image: Riccardia levieri

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��Bryophytes lack true roots. �In primitive forms there are unicellular rhizoids, while in advanced forms the rhizoids are branched and multicellular. �These rhizoids help in anchorage and absorption.�Image: Targionia hypophylla � Smooth Tuberculate Branched (Mosses)

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�The entire thallus is leaf like in primitive bryophytes

Cheilolejeunea intertexta

Part of Gametophyte

Part of the ventral plant showing arrangement of leaves and underleaves.

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�In advanced forms leaves are spirally arranged and are called microphyll. The microphyll is a small leaf with median midrib.�

Plagiominim

Pyrrhobryum spiniforme

The narrow leaf has a strong,�conspicuous midrib, and�prominent teeth along the�margins.

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The plant body of bryophytes consists of simple parenchymatous tissue with NO vascular tissues like xylem and phloem.�

Liverwort T,S. of Thallus

Hornwort: T.S. of Thallus

Moss: T.S. of Leaf

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Bryophytes reproduce vegetatively with the help of tubers, bulbils, protonemal branches, fragmentation etc

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�Sexual reproduction is oogamous type. �The sex organs of bryophytes are called gametangia. �Which are multicellular with sterile jacket.�Female gametangium is known as archegonium. �Male gametangium is known as antheridium.�

Antheridium

Archegonium

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��Antheridium is club shaped. �It shows a basal stalk and a dome shaped body covered by jacket enclosing androcytes which develop spermatozoids. �Spermatozoids are small, slender and biciliate.�

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��Archegonium is flask shaped. It has a basal small stalk, median swollen venter and a terminal long neck. �On the bod axis archegonium has axial row of neck cells, ventral canal cell and egg. �The venter wall enlarges with the developing embryo to form protective envelop called calyptra.�

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Fertilization is possible in the presence of water. The egg is fertilized by the actively swimming motile spermatozoids while it is still within the archegonium.�

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�The fertilized zygote develops into sporophyte. Sporophyte is diploid, multicellular and not well defined. �Sporophyte has a distinct foot, seta and capsule (Mosses, Marchantia), only capsule (Riccia) and foot & Capsule (Anthoceros).

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Sporophyte remains attached to the gametophyte throughout its life and is dependent on it.

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Reduction division takes place in the developing sporophyte which results in the formation of haploid spores.

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All the spores produced in a sporophyte are morphologically alike.�

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�Life cycle of bryophytes is haplodiplontic with heteromorphic alternation of generation of multicellular generations.�

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Classification (As per G.M. Smith, 1955)

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Characters of Hepaticae �(Hepaticopsida)

Gametophytes either flattened thalli

or leafy shoots.

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2. The flattened ribbon-like to leaf-like thallus of the thallose liverworts are either simple or structurally differentiated into a system of dorsal air chambers and ventral storage tissues.

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��The dorsal epidermis of the thallus is punctured with scattered pores that open into the air chambers.�

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��In the leafy forms, the leaves are arranged on the stem in one ventral and two lateral rows or ranks. �The leaves are one cell layer thick throughout, never have a midvein and are usually divided into two or more parts called lobes.

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The ventral leaves which actually lie against the substrate, are usually much smaller than the lateral leaves that are hidden by the stem.�

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Rhizoids are hyaline (colourless), unicellular and unbranched.

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Liverworts synthesize a vast array of volatile oils, which they store in unique organelles called oil bodies. These compounds impart an often spicy aroma and seem to discourage animals from feeding on them.�

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Sporophytes develop completely, enclosed within gametophyte tissues until their capsules are ready to open.�

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The seta, which is initially, very short, consists of small thin-walled, hyaline cells, elongates its length up to 20 times its original dimensions just prior to spore release.

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The rapid elongation of seta pushes the darkly pigmented capsule out of the gametophytic tissue.

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With drying, the capsule opens by splitting into four segments or valves.�

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The spores are dispersed into the winds by the twisting motions of numerous intermixed sterile cells, called elaters.�

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The liverworts disperse the entire spore mass of a single capsule in just a few minutes.

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Characters of Anthocerotae (Anthocertopsida) Hornworts

Gametophytes are: simple, flat, lobed and unspecialised thalloid.

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The thallus shows a uniform internal tissue organisation.

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��Colonies of symbiotic cyanobacterium, Nostoc fill small cavities that are scattered throughout the ventral part of the thallus. �These colonies appear as scattered blue-green dots when the thallus is viewed from the top.�

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��Hornworts differ from all other land plants in having only one large algae-like chloroplast (chloroplasts with pyrenoids) on each thallus cell.�

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Like liverworts, the rhizoids are hyaline unicellular, and unbranched.�

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Sporophytes are very strong and lasting for several weeks. Hornworts get their name from their long, horn-shaped sporophytes.�

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The sporophyte is differentiated into a long cylindrical capsule and a bulbous foot.�

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�At the base of the sporangium, just above the foot, is a mitotically active meristem, which adds new cells to the spore-producing zone throughout the lifespan of the sporophyte.�

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�The sporangium releases spores at its apex, at the same time the new spores are being produced by meiosis at its base.�

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�� With drying, the capsule opens by splitting into two segments or valves.�Release of spore takes place gradually over a long period of time, and the spores are mostly dispersed by water movement rather than by wind. �Pseudoelaters perhaps take place in spore dispersal.�

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Characters of Musci (Bryopsida) Mosses

The mature gametophyte is differentiated into an upright branched axis and spirally arranged leaves.

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The stem is differentiated into a central strand of thick-walled water conducting cells, called hadroids, surrounded by a parenchymatous cortex and a thick- walled epidermis.

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The leaves are simple small sessile and with a distinct midrib. The lamina is only one-cell layer thick.

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The rhizoids are multicellular, branched and reddish-brown in colour.

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The sporophyte is differentiated into foot, seta and capsule.

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The seta tears the archegonial enclosure early in development, leaving the foot and base of the seta embedded in the gametophyte. The elongated seta raises the capsule much above the gametophyte.

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The sporophytes are strong and long- lived, lasting several weeks.

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With drying, the capsule breaks open at its tip. The peristome teeth are folded down into the spore mass and then bend outward, dispersing the spores into the drying winds.

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The spores can travel long distances on wind.

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In mosses, cell specialization occurs within the protonema to form a horizontal reddish-brown anchoring filaments called caulonemal filaments and upright, green filament, called chloronemal filaments. Subsequently, some cells of the caulonemal filaments specialized to form leafy buds that will ultimately form the adult gametophytic shoots. So numerous shoots develop from each protonema.

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Gametophyte

Sporophytes

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Life cycle of bryophytes is haplo-diplontic with heteromorphic alternation of generation.
In each cycle, a haploid gametophyte, each of whose cells contains a fixed number of unpaired chromosomes, alternates with a diploid sporophyte, whose cell contain two sets of paired chromosomes.
Gametophytes produce haploid sperm and eggs which fuse to form diploid zygotes that grow into sporophytes.
Sporophytes produce haploid spores by meiosis, that grow into gametophytes.

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ADAPTAION TO LAND HABIT:�

Bryophytes are the oldest of all lineages of land plants and are believed to be the closest connecting link between land and aquatic plants.
Due to their soft tissues fossil records of bryophytes are very meager but the oldest fossil records that have so far been found can be dated back to almost 500 million years ago.
Spore-like structures were found in Argentinian rock dated to 473-471 million years old.
Fossilized mosses appear much more recently between 299-250 million years old. It is quite possible that the Bryophytes are significantly older due to their poor preservation.
It is believed that Bryophytes evolved from green algae but genetic analysis has shown they do not share the same common ancestor and in some cases they are only distantly related.

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Economic Importance of Bryophytes

1. Ecological importance in succession - pioneers in establishing vegetation in the barren rocks.

2. Prevent soil erosion

3. Provide food - Some mosses provide food for herbaceous mammals, birds and other animals

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4. Good Packing material – Sphagnum used to pack bulbs, cuttings and seedlings for shipment

5. Used in seed beds and green houses.

6. Source of fuel - Sphagnum provide peat which is a potential source of coal and used as fuel.

7. Absorbent bandages - Sphagnum plants are slightly antiseptic and possess superior absorptive power.

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A number of morphological features link the migration of bryophytes from aquatic environments on to land.

a) Similarities to land plants: Distinct adaptations observed in bryophytes have allowed plants to colonize Earth's terrestrial environments.

To prevent desiccation of plant tissues in a terrestrial environment, a waxy cuticle covering the soft tissue of the plant provides protection.
The development of gametangia provided further protection specifically for gametes.
They also have embryonic development which is a significant adaptation seen in land plants and not green algae.
While bryophytes have no truly vascularized tissue, they do have organs that have specific functions, similar to those functions of leaves and stems in higher level land plants.

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b) Similarities to aquatic plants: Bryophytes also exhibit connections to their aquatic ancestry.

They share various features with their green algae ancestors.
Both green algae and bryophytes have chlorophyll a and b, and the chloroplast structures are similar.
Like algae and land plants, bryophytes also produce starch and contain cellulose in their walls.
Bryophytes depend on water for reproduction and survival.
A thin layer of water is required on the surface of the plant to enable the movement of sperm between gametophytes and the fertilization of an egg.

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The adaptation have helped to make the move from water to land possible to land habit or sub aerial life of bryophytes involves the development of following features.

1. Protection against desiccation: A waxy cuticle covering the soft tissues of the plant provides protection and prevents desiccation of the tissues and bryophytes by reducing loss of water by evaporation.

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2. Gametangia:

They also have embryonic development which is a significant adaptation seen in land plants and not green algae.
The development of gametangia provided specifically for gametes.
Connections to their aquatic ancestry are also evident through their dependence on water for enabling the movement of sperm between gametophytes and the fertilization of an egg and survival.

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3. Development of organs for attachment and absorption of water:

Rhizoids are developed for of absorption of water and anchorage of thallus.
Scales are developed for the retention of water to avoid desiccation of thallus during scarcity of water.

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4. Formation of a compact multicellular plant body and conservation of water:

It helped in the conservation of water by reducing cell surface area exposed to dry land conditions.

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5. Absorption of CO2:

Photosynthetic tissues are modified into special chambers for the absorption of carbon dioxide without losing much water and exposure to light.

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6. Heterogamy (Production of two types of gametes):

It is evolved, forming non-motile egg containing stored food and motile sperms.

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7. Protection of reproductive cell (gametes) from drying and mechanical injury:

It is given by the special multicellular organs (antheridia and archegonia) having jacket layer.

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8. Production of the thick-walled, tetrahedral wind disseminated spores inside an envelope:

Spores have been recovered from the Ordovician Period and these too find a counterpart among extant liverwort lineages. The microfossil records suggests that bryophytes and in particular liverworts, were integral parts of the earliest plants.

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9. Primitive vascular system from the conducting strands.�

10. Multicellular Embryo is retained inside the female reproductive body during its development

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11. Alternation of generation:

Alternation of gamete producing generation (gametophyte) with spore producing generation (sporophyte) enables the plant to produce and test the best genetic combinations for adapting to the versatile (multipurpose) terrestrial conditions.

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Evolution of bryophytes is marked by a trend of reduction of the gametophyte and predominance of the sporophyte in next plant gropus i.e. Pteridophytes, Gymnosperms and Angiosperms.

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Ecological Importance:

Characteristics of bryophytes make them useful to the environment. Depending on the specific plant texture, bryophytes have been shown to extremely important in the early stages of ecological succession.
In xerosere or lithosere bryophytes are pioneers in establishing vegetation on the barren rocks.
They form uniform dense patches or mats on the soil surface thereby reducing erosion and evaporation of water which helps to improve the water retention and air space within soil, making more available for succeeding plants.
Peat mosses are the dominant plants of extensive northern wetland areas and largely responsible for the development of bogs.

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Many bryophytes are playing an important role as bioindicators. Just as bryophytes will readily absorb water and nutrients through their surfaces, so will they also readily absorb a wide variety of potentially toxic compounds.
The effects of pollutants vary, depending on the pollutant and the species of bryophytes but, even within species there are variations. Some populations are more resistant than others.
Mosses have become important in monitoring the health of ecosystems. They are used in pollution studies to indicate soil pollution (such as the presence of heavy metals), air pollution, and UV-B radiation.

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Mosses add green aesthetic value to the forests. Moss Gardens in many countries are designed to create peaceful sanctuaries.
Some bryophytes have been found to produce natural pesticides e.g. Plagiochila, produces a chemical that is poisonous to mice.
Some bryophytes produce chemicals that are anti-feedants which protect them from being eaten by slugs.
Phythium sphagnum is sprinkled on the soil of germinating seeds, to control growth of "damping off fungus" which would otherwise kill young seedlings.

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Bryophytes as food and shelter: �

Many herbaceous mammals, birds and other animals make use of bryophytes for food and shelter. Numerous invertebrates eat bryophytes, lay their eggs on them or shelter in them. Some birds use bryophytes as a vital part of the construction material of the nest.
As mosses have a low nutritional value they are usually ignored by the larger animals when other food is available. But some arctic animals (including reindeer) scoff moss down. Barnacle geese that migrate north to arctic breeding grounds start eating mosses which contain high levels of arachidonic acid a natural antifreeze compound, which helps cells to keep working at low temperatures.

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Commercial Importance of �Peat Moss Sphagnum:

Fuel: Peat is a fuel produced from dried bryophytes, typically Sphagnum which is a potential source of coal and used as fuel. In northern Europe, compressed peat briquettes are used in fireplaces and stoves. In Ireland, peat is still extensively used for cooking as it burns very cleanly and also about 95% peat is burned to generate electricity.
Soil Fertility and Water Holding Capacity: Peat is also highly valued as a conditioner of inorganic soil and to increase soil fertility. As it absorbs and retains large amount of water readily, peat improves the water-holding capacity of soil.

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Packaging: Bryophytes antibiotic properties and ability to retain water make them a useful packaging material for vegetables, flowers, bulbs, cuttings and seedling for transportation.
Wound Dressing: Peat mosses are characteristically acidic which prevents the growth of most bacteria. Due to the antibiotic, antiseptic properties and superior absorptive power dried Sphagnum has been used by indigenous peoples for diapers and was used as a surgical dressing in the First World War.

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MORPHOLOGY, ANATOMY AND LIFE CYCLE (EXCLUDING DEVELOPMENTAL STAGES) OF FOLLOWING TYPES�

A] HEAPATICOPSIDA: RICCIA