BRYOPHYTES AND TRACHEOPHYTESBiology Class IX

7/15/2015EducastLubna Naz

Chapter #4

BRYOPHYTES AND TRACHEOPHYTES

Contents:

a. Bryophytes b. General Characteristicsc. Classificationd. Classificatione. Tracheophytes(Vascular Plants)f. General Characteristicsg. Classificationh. Spermatophytes(The seed producing Plants)i. Angiospermj. Monocot Plant k. Dicot Plantl. Importance of vascular plants

Learning objectives:

• Algae and Fungi. • General characters of fungi with reference to Rhizopus, Penicillium, Agaricus, Ustilago. • Importance of fungi. • General characters of algae with reference to Chlamydomonas and Spirogyra. • Economic importance of Algae.

BRYOPHYTA

The word bryophyte refers to a group of plants comprising the mosses, liverworts, and hornworts. These plants do not flower and therefore, never produce seeds. Bryophytes do not have a true vascular system and are unable to pull water and nutrients up from the ground at any significant distance. A plant that does not flower is called a cryptogamand reproduces by spore production. The process by which they produce spores is termed alternation of generations. There are several characteristic features of bryophytes. First, the green tissue that makes up most of the plant body is not vascularized; it does not have xylem and phloem cells. This absence of specialized tissues for transporting water and dissolved food throughout the organism limits terrestrial forms to being very short plants, since the only way to move substances through the plant body is by osmosis and diffusion from surface moisture.

Second, bryophytes do not have roots, but have rhizoids, which are relatively simple, sometimes multicellular filaments of thin-walled cells that extend from the photosynthetic tissue into the soil or other substrate . They anchor the plant somewhat and in some cases facilitate water and nutrientuptake.

All plants undergo a life cycle that takes them through both haploid and diploid generations. The multicellular diploid plant structure is called the sporophyte, which produces spores through meiotic (asexual) division. The multicellular haploid plant structure is called the gametophyte, which is formed from the spore and give rise to the haploid gametes. The fluctuation between these diploid and haploid stages that occurs in plants is called the alternation of generations. The way in which the alternation of generations occurs in plants depends on the type of plant. In bryophytes (mosses and liverworts), the dominant generation is haploid, so that the gametophyte comprises what we think of as the main plant. The opposite is true for tracheophytes (vascular plants), in which the diploid generation is dominant and the sporophyte comprises the main plant.

CLASSIFICATION OF BRYOPHYTES

According to the latest recommendations of ICBN (International Code of Botanical Nomenclature), bryophytes have been divided into three classes.

1. Hepaticae ( Hepaticopsida = Liverworts)

2. Anthocerotae (Anthocertopsida= Hornworts)

3. Musci (Bryopsida= Mosses)

EXTERNAL STRUCTURESPlant is small about 1-3 cm long, stem is erect and branched. It is differentiated into rhizoids, axis, and leaves. The rhizoids are multicellular and branched. The axis is aerial, erect, and branched. The leaves are simple, small, and spirally arranged. The upper leaves are large and lower leaves are crowded.

INTENAL STRUCTUREStem

The outermost layer is epidermis contain chloroplast. Below the epidermis there is multilaered parenchyma called cortex. In the centre there is compact and narrow cells without protoplast called central cylinder which factions as conducting tissue.

Leaves: The leaf lamina consists of single layered parenchyma rich in chloroplast and the midrib contains central strand.

ReproductionAsexual method of reproduction takes place by following methodBy primary protonema: 

The spores germinate to give rise small filament called primary protonems, which contains small buds from where new plant is produced.By secondary protonema: 

The filament can grow from stem, leaves, or rhizoids called secondary Protonems. They bear small buds and which are capable to give rise new plant.By gemmae:

 The small multicellular structures develop on leaves and axis, which develop into new plant.By bulbil:

 The gammae like structures developed on the rhizoids are called bulbils which grow into new plant.

Sexual reproductionFunaria is monoecious female organs develop or separate branch of same plant autocious.Male branch – the branch with male sex organs id called male branch.

The male sex organs –

Antheridia develop in group at the apex of shootThey are mixed with hair like structure paraphysis.Antheridia and paraphysis are surrounded by leaves called perichaetial leaves.

Each antneridiuim is stalked, club-shaped, surrounded by jacket; two apex cells are large/thick called operculum. With the help of water, the operculum ruptures and androcytes come out and change into antherozoids (spermatozoids).

Female branch 

The branch with female sex organs.

The female sex organ – Archegonia are developed at the apex of shoot.The archegonia are mixed with hair like sterile structures called paraphysis.Both surrounded by perichaetial leaves.

Each archegonium is flask shaped, stalked, and contains broad Venter and long neck. The Venter contains an egg, Venter canal cell, double layered wall. Neck contains neck canal cells.

FertilizationIn pressure of water antherozoid reach to archegonia tip. Neck canal/Venter canal cells degenerate. antherozoids enter through neck and only one free with egg to form zygote.

SporophyteThe zygote secrets thick wall around it called oospore, which grows into a saprophyte. The mature saprophyte consists of foot\seta\capsuleFoot – it is barrel, conical shaped, embedded in apex of a branch.Seta – it is very long, twisted, and slender.Capsule– pear shaped in structure and it consists ofApophysis – it is multicellular thick basal portion of the capsuleColumella– it is central portion of the capsule surrounded by spore sac.Spore sac– it is a sac containing spores on either side of columella. On the outer side of the spore sac air spaces are present separated by partition wall.Operculum – apical region of capsule. It is conical lid of the capsule. It consists of small teeth called peristome.

Dehiscence of capsule – At maturity annulus breaks and the operculum is thrown away. The spores are liberated out.

Spore germination

Under favorable condition the spore, germinate to produce small filament. The filament branches freely called primary protonema. The primary protonema gives small buds. Each bud gives rise into new Funaria plant.

TRACHEOPHYTES(VASCULAR PLANTS)\

They are the vascular plants (those having xylem and phloem tissues) that reproduce by releasing spores rather than seeds, and they include the highly diverse true ferns and other graceful, primarily forest-dwelling plants. There are about eleven thousand different species of pteridophytes, making them the most diverse land plants after the flowering plants (angiosperms). Pteridophytes may represent the closest living relatives (sister group) to the seed plants. (Seed plants include the angiosperms, the conifers, and a smaller assortment of other plants.)

Pteridophytes range greatly in size. There are tiny floating ferns used as "green fertilizer" in rice paddies because they partner with bacteria that pull nitrogen from the air and "fix" it in chemical

compounds that other plants can use. In some tropical forests, the largest plants are tree ferns that can be up to 30 meters (100 feet) tall and have huge spreading leaves up to 4.5 meters (15 feet) in length. Pteridophytes also show a transition from simple to complex leaves. Some pteridophyte groups, including the club mosses and horsetails (classes Lycopodiopsida and Equisetopsida), have simple microphyllous leaves, featuring a single, unbranched vein and modest vascular supplies that do not cause breaks or gaps in the stem vasculature.

All pteridophytes have a true alternation of generations, in which a dominant sporophyte generation produces spores through meiosis , and a free-living gametophyte generation forms gametes (egg and sperm) by mitosis . Ferns can be used to illustrate the life cycle stages common to all pteridophytes. Diploid (2n) fern sporophytes are familiar to most people and are often found as quiet accompaniments in floral arrangements. When mature, the undersides of fern leaves produce clusters of capsular structures called sporangia, within which meiosis forms the haploid (n) spores. These spores are released from the sporangia, often when dry wind currents cause the active snapping of the capsules, lofting the spores into the air.

Spores that are wind-borne to shady, moist habitats germinate and yield multicellular, but microscopic, gametophytes, the sexual stage of the life cycle. These short-lived, delicate plants mature and produce egg-forming archegonia and sperm-producing antheridia. When water is present, multi-flagellated sperm swim from mature antheridia, are chemically attracted to the necks of the archegonia, and fertilize the eggs. Although frequently bisexual (hermaphroditic), in most cases the sperm produced by a gametophyte cannot successfully fertilize its own eggs and must swim to archegonia on neighboring, genetically different gametophytes. The diploid zygotes , produced by the fusion of haploid egg and sperm, divide mitotically and differentiate into mature sporophytes, completing the life cycle.

Although most pteridophytes are homosporous (produce spores that are all the same size), a few groups are heterosporous with large megaspores and small microspores. The megaspores produce megagametophytes that only form eggs, and microspores only produce microgametophytes and sperm. Heterospory evolved independently in several groups of vascular plants, including all members of the orders Selaginellales and Isoëtales and those in a few fern groups (the families Marsileaceae and Salviniaceae of the class Filicopsida). The most successful origin of heterospory ultimately resulted in the great diversity of seed plants.

PTERIS:1.   The plant body consists of root, stem and leaves. It is      Sporophytic in nature.2.   The leaves are larger in size called Fronds.3.   The stem is underground and called Rhizome.4.   The leaves are compound in nature i.e. they are divided      Into many small leaflets called Pinnae.5.   On the mature leaves small dark brown bodies areProduced called Sori. These are the groups of sporangia.The mature leaves wich prodiced sori called Sporophyll.

ADIANTUM:Introduction:Adiantum resembles to pteris plant, but its leaflets are broad andArranged in alternate manners. It grows in wild condition.

Structure:Adiantum is a herb plant. It is a sporophyte plant which consists ofThree parts:1.   Stem2.   Root3.   Leaves1.   Stem:It is short, thick and grow under the soil called Rhizome.

2.   Root:The roots are arise from the lower region of Rhizome. These are Fibrous Adventious Root (non-true roots).

3.   Leaves:The leaves are large and compound. They are divided into many leaflets which is called pinnar/ these pinnae. These pinnae are arrange in alternate manners on a central branch called Rachis Sometime the lower pinnae again divided into further small leaflets called Pinnules.

SORI:At the time of reproduction mature leaves sporophyll produced small radish brown bodies calkled Sori. Sori are the groups of Sporangia. Each sporangia. Each sporangium produces many spores.The spores become free by the rebturing of sporangia wall.Each spores germinates and developed into Prothallus which is the gametophyte of fern (adiantum).

S.No Angiosperm Gymnosperm

    1

Covered Seed:Angiosperms are the plants whichProduced covered seed inside the fruit.

Naked Seed:Gymnosperms are the plants which produced naked seeds because ovary is absent.

    2 Fruits:Their ovules are produced within ovary, which is converted into fruit.

Non-Fruits:Their ovules are without ovary, so fruit is absent.

    3 True Flower:They produced flowers with calyx,Corolla, androcium, gynocium.

Cone Like:Their flower are cone like do not produced calyx, corolla, andocium and gynocium.

    4 Mesophytes:These plants are grow in land areaWhere water present in sufficientAmount.

Xerophytes:They grow on cold climate where water isNot present in sufficient amount.

Some angiosperm flowers such as roses and gardenias are quite

showy and fragrant.

Some of the more commonly found examples of gymnosperms are pines, spruces, cedars and sequoias. 

PINUSGeneral Morphology:The plant belongs to the sprophytic generation and is differentiated into root, stem and leaves. The adult cycas plant is about 2 meters high.. The stem is thick, unbranched (caudex, but branches may arise when terminal bud is injured) and bears triangular leaf bases on its surface. The leaves show circinate vernation(the arrangement of the foliage leaves within a bud.) and are loosely arranged. Cycas leaves are of two types (a) scale leaves (b) green foliage leaves. The number of foliage leaves formed in one year will be constant for any given species.The petiole is stout and called rachis. Rachis bears leaf lets or pinnules on either side. The lower leaf-lets of rachis are modified into spine. Lateral veins are absent in pinnule. The primary root persists and forms a tap root system. The lateral branches of the root come out of the soil (apo-geotropic) and branch repeatedly to form dwarf dichotomously branched coral like man called coralloid roots or corallrhiza. Blue green algae Anabaena live symbiotically in the coralloid roots. It fixes the nitrogen.General Anatomy:The vascular bundles in stem are conjoint, collateral open and arranged in a ring. The xylem of the bundles consists of tracheids only. The pholem comprises of sieve tube and phloem parechyma, they lack companion cells. The secondary growth in a young stem is normal, but as it becomes older, new rings are formed giving rise concentric rings of secondary vascular tissues (polyxylic condition).Transfusion tissue is present in the leaves which help in conduction. Tough and leathery texture and other structures such as strongly cutinized thickend hypodermis, sunken stomata restricted only to the lower surface, presence of transfusion tissue all these point to a xerophytic adaption of cycas.Internal Structure of Pinnule:Show xerophytic nature. Mesophyll is differentiated into palisade and spongy tissue. Vascular bundle of innule is conjoint, collateral, xylem is diploxylic, the larger patch is the centripetal xylem and the two lateral patches are centrifugal xylem. Phloem is present below the centrifugal xylem.Anatomy of Root:Resembles that of a dicot root. Xylem is diarch or triarch. In the coralloid root, the algal zone is in the cortex, which is termed as middle cortex.

Sexual Reproduction:Male cone:Cycas is dioecious. The male plant has a cone at its apex. Each cone has a thick central axis around which microsporophylls are spirally arranged. Groups of sporangia or sori are present on the abaxial (lower) side of the sporophyll.Each sorus contains 2-6 sporangia or anthers which are filled up with pollen grains or microspores. Microspore represents the first cell of male gametophyte stage. The upper part of microsporophyll is sterile and pointed called apophysis.Female Cone:There is no true female cone is cycas. The megasporophyll arise at the apex of the female plant and are loosely arranged in rosette manner. On either side of the broader part of sporophyll 4-6 red coloured ovules or megasporangia are arranged. Cycas ovule has a single, thick three layered integument which is hard and inner layers are fleshy and the middle layer is hard and stony.Deep in the nucellus of the mature ovules lies the megaspore mother cell which divides into four megaspores. Only one of the four megaspores is functional and rest three degenerate. By repeated divisions of the functional megaspore, female gametophyte is formed. On the upper surface of the female gametophyte. 2-8 archegonia are formed, each having a ventral cell and an egg.Fertilization:The pollen grains reach the ovule through the medium of air. The method of fertilization in said to be siphano-zooidiogamy (because of multiciliate antherozoids and tube). In Cycas polyembryony is often seen as egg of almost all the archegonia are fertilized and produce embryo. In Cycas, alternation of generation in quite prominent.Vegetative Reproduction:Bulbils (resting adventitious buds) are produced on the stem in the axil of scale leaves. They break up from the parent plant and germinate to give rise to new plant.PinusGeneral Morphology:The Pinus tree represents the sporophytic generation. The stem displays the excurrent habitat. The main stem is branched. Branches are of two types:(a) Long branches:Branches with unlimited growth (grow by means of apical bud)(b) Dwarf branches:Branches with limited growth, arising directly from the trunk.Leaves are also of two kinds:

(a) Foliage leaves:These are unusual type being long, narrow, tough, green and are frequently known as Pinus-spur or Pine-needles. They are borne only on the dwarf shoots in clusters of two (P. merkusii), three (P. roxburghii) or five (P. wallichana).Branches with foliage leaves are called spurs. Spurs could be monofoliar, bifoliar, trifoliar, pentafoliar having 1, 2, 3, 5 foliar leaves.(b) Scale leaves:These are brown, membranous and are protective in function. These are borne on both type of branches, but they fall off as the dwarf shoots mature. Scale leaves of dwarf shoots are called cataphylls.Primary root persists and forms a typical elongated straight tap root. Mycorrhizal roots develop like that of cycas.General Anatomy:It is composed of small pith, a thick vascular cyclinder made up of a ring of separate collateral and open vascular bundles. Well developed resin canals are present in the stem. Primary xylem contains neither true vessels (tracheae) nor wood fibres which characteristic of angiosperms. Mesophyll cells not differentiated into palisade and spongy tissue in the leaves. Resin canals and transfusion tissue are present in the leaves.Anatomy of Root: Resembles dicots. There are 2, 3 or 4 (diarch, triarch or tetrach) exarch bundles (more or less Y shaped) with alternating xylem and phloem (radical). Pith is generally absent. In the apical root meristem there is no dermatogen.Sexual Reproduction:Pinus is monoecious, it bears male and female reproductive cones on the same tree but on separate branches.Male cone:It is shortly stalked and consists of an elongated central axis, bearing a number of small spirally arranged and closely fitted scale-like microsporophylls. Numerous winged microspores are produced from microspore mother cell in the microsporangium.Male gametophyte:The microspore nucleus divides into a small protallus cell and a large central cell. The nucleus of large central canal cell called the antheridial cell divides into a generative cell and a tube cell.Tube cell:The tube cell grows out to form a delicate pollen tube which grows into the nucellar tissue upon which it now depends for its nourishment and protection. The pollen tube rests for about a year in this condition because the ovule is not yet ready for fertilization.

Hence further growth of microgametophyte is arrested. It rests throughout the late summer and following winter resuming activity in the following April (second year).The tube becomes active again and it penetrates the nucellar tissue. The generative cell divides to give rise to a barren stalk cell (sterile cell) and a fertile body cell (Spermatogenous cell). The body cell along with protoplasmic contents of the tube and stalk cell pass down the pollen tube. The body cell divides into two unequal cells, which are the male gametes. The gametes are formed only a week before the fertilization.Female cone:Arise singly or in a small cluster of two to four, each as a bud in the axial of the scale leaf towards the end of the new shoots of unlimited growth which do not bear the male cones. The female cones are very slow in growth. They take almost a year to be mature enough to receive the pollens. The central axis bears paired scales in a close spiral.Bract scales or Carpellary scales (Each corresponding to a carpel or megasporophyll), lower scale, small, leathery, brownish scales.Ovuliferous scales:It bears two sessile ovules on its upper surface at the base. Each ovule is orthotropous, and consists of a central mass of tissue the nucellus, surrounded by single integuments made of three layers.Pollination:Takes place in March/April in Eastern Himalayas. The amount of pollens liberated by the pine forests at this time is prolific so that the air gets saturated with them and there is a yellow deposit of pollens on the forest floor. This phenomenon is known as 'sulphur-shower'.Pollination drop:As the ovule matures for the pollination, the nucellar cells dissolve just below the micropyle. The dissolved tissue becomes mucilagenous and project out through the micropyle in the form of a droplet and is called pollination drop.Fertilization:The pollen tube on reaching the archegonial neck (which takes place a year after pollination i.e. two years after the female cone first emerged) the pollen tube destroys the neck cell. Just before fertilization, the body cell divides into two nake male cells or gametes.Simple polyembryony:(A number of embroys from a number of fertilized eggs) is common is some genera of Pinaceae viz. Larix & Picea but is Pinus (also Cedrus) the proembryo tires split from one another-into 4-along the 4-cells of each tire giving rise to 4-separate embryos. This is known as cleavage polymebryony. Usually one of these embryos survive in the seed.

ANGIOSPERMAngiosperms (Gr. Angeion: case; spermos: seeds) are a group of plants characterised by production of flowers and formation of seed(s) within a fruit. The plant body is highly complex showing a great range in size and diversity in form. This led to the morphologic and physiologic differentiation between various parts of plant body, which gave rise to a plant organ concept. The plant body is the sporophyte which is made up of several fundamental parts or organs.The morphologists divide the plant body into three basic organs- the root, stem and leaf. The main axis of the plant body consists of a root, normally developing under the ground, and a stem normally growing up. The root bears a number of lateral structures similar to it and forms the root system. The stem holds lateral appendages in the form of leaf and branch.The stem along with leaf is called the shoot and forms the shoot system. The root system and the shoot system together constitute the vegetative body of the angiosperm. As the plant grows and reaches maturity, it forms flowers, fruits and seeds. These three constitute the reproductive system of the plant as the flower forms the fruit and seed after fertilisation. The seed when germinates, gives rise to new plant and serves the function of multiplication of the plant.