Bryophytes and Tracheophytes

Chapter 06

BRYOPHYTES AND TRACHEOPHYTES

Plants are the connecting link between inorganic and organic world. They are all autotroph and manufacture food for all forms of life hence called producers. The constitute the most important link in ecosystem.

Learning objects:

General characters of Kingdom Plantae.The two groups of plants.

General account of Bryophytes with reference to Funaria.General account of Tracheophytes and their major groups.

Study of pteridophyte with reference to Pteris, Adiantum.Characteristic feature of Spermatophyte.

Gymnosperms and study of pinus and Thuja.

General characters of flowering plants and their different paits.Morphological differences between dicots and monocots.

6.1BRYOPHYTES (Bryon = a moss; phyton = plant)

Bryophytes and tracheophytes are included in Kingdom Plantae. Both have well developed embryos which give rise to their plant bodies.

Bryophytes are defined as multicellular, eukaryotic, chlorophyllous, non-vascular plants having cell-wall made up of cellulose and their zygotes develop into an embryo.

Plants are multicellularphotosynthesizers that are adapted to living on land. AH plants protect their embryos from dessication.

6.1.1 General Account of Bryophytes:

Bryophytes are the simplest group of plants. They are relatively poorly adapted to life on land, so are mainly confined to damp shady places. They are amphibious needing water for sexual reproduction. They have thalloid bodies which are not differentiated into true root, stem and leaves. Instead of roots, they have unicellular hair like structures called rhizoids. Some bryophytes have pseudo stem and leaves. They do not have vascular bundles.

All plants have a life cycle that shows an alternation of generations; some have a dominant gametophyte and some have a dominant sporophyte.

Bryophytes show distinct heteromorphic alternation of generation. It means the two generations called gametophyte and sporophyte are morphologically as well as cytologically different. In contrast to other plants, bryophytes have main generation gametophyte (Haploid). The gametophyte reproduces sexually by producing dissimilar male and female gametes. These two fuse to form zygote, which develops into well protected embryo. This gives rise to sporophyte, which may be partly or completely dependent on gametophyte. Spores are produced in sporophyte after meiosis. Each spore germinates into a gametophyte. Bryophytes are classified into three groups.

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BiologySindh Text Book Board, Jamshoro.

Funaria:

Gametophyte consists of rhizoids, pseudo stem and leaves. The stem may be branched. Male sex organs called Antheridia (singular-antheridium) are located at the apex of male branch and female sex-organs called archegonia (singular - archegonium) at the tip of female branch.

Fertilization takes place when plant is submerged in water. Zygote is formed inside archegonium, which develops, into an embryo. Embryo develops into a sporophyte, which remains attached with gametophyte. Sporophyte consists of foot, seta and capsule. The foot is anchored to the gametophyte and absorbs nutrients from it. Seta elevates the capsule in the air. Within capsule spores are formed after meiosis. Due to dehydration, capsule burst open and spores are liberated. Each spore germinates into Funaria gametophyte.

6.2TRACHBOPHYTES (VASCULAR PLANTS)

6.2.1 General characters:

Tracheophyte (Trachea = Vessel; Phyton = Plant) have conducting or vascular tissues. You have already studied that xylem and phloem are types of two conducting tissues which are not only responsible for the conduction of material but also give rigidity and support to the plant body.

Nearly, all tracheophytes have well developed true root, stem and leaves. They vary greatly in height ranging from miniature to giant size like Sequoia (Red wood tree). All tracheophytes show alternation of generation in which sporophyte generation is dominant and totally independent, whereas gametophyte generation may be very small, inconspicuous, short lived and totally dependent on sporophyte except in pteridophytes. The zygote develops into well protected embryo from which young plant is produced.

6.2.2 Major groups of tracheophytes:

Tracheophytes are divided into pteridophytes and spermatophytes. Pteridophytes are non-seed producing plants. They are further divided into psilopsida, lycopsida, sphenopsida and pteropsida.

Pteropsida (Ferns) are the common and important group of pteridophyte. They are found growing in nature or in moist cool, shady places. The common examples of ferns are Dryopteris, Pteris, Adiantum, Marsilea etc.

In the non seed vascular plants, such as ferns, there is a dominant vascular sporophyte, which produces wind-blown spores. These plants have an independent nonvascular gametophyte produce flagellated sperm swim in external water to reach the egg.

i) Pteris:

It is found in wild state in some regions of Punjab but in Sindh it is a common ornamental plant. The main plant is a sporophyte having adventitious roots, under ground stem-rhizome, pinnate compound leaves called fronds and sporangia in sori found under the surface of sporophyll (sporangia bearing leaves).

ii) Adiantum:

It grows in the wild. It resembles with pteris except the shape of leaflets, which are comparatively broad and arranged alternately.

The main plant is sporophyte, a small herb which consists of a stem, roots and leaves.

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Stem — short, thick, rhizome.

Roots— fibrous and adventitious, arise from the lower side of rhizome.

Leaves— large and pinnately compound, having rachis bearing leaflets or pinnaearranged in an alternate manner. Lower pinnae are further divided into number of pinnules.

Sori— on the under surface of the margin of fertile pinnules occur the sori. Eachsorus consists of a number of small spore producing bodies sporangia.

Spores after liberation from sporangium develop into small gametophyte called prothallus.

6.3 SPERMATOPHYTES —The seed producing plants:

Spermatophytes (Sperma = Seed, Phyton = Plant)are seeds producing plants, which are divided into two major groups, gymnosperms and angiosperms.

This division is based whether ovules are naked or covered. This gives rise to naked or covered seeds. The covering structure is called ovary, which develops into fruit in angiosperms.

6.3.1 Gymnosperms: (Gymnos = Nakecf; Sperma = Seed)

Gymnosperms have naked ovules produced in cones. Ovules develop into naked seeds as fruit is absent due to the absence of ovaries. We will study Pinus as the representative of gymnosperms.

Among the first seed-producing plants were the gymnosperms, which produce naked seeds. The four divisions of these plants are probably not closely related.

PINUS:

Pinus plant is very tall and thick. The height may be 40 to 50 meters and thickness may be up to 2 meters. It has well- developed root, stem, leaves and reproductive bodies called cones/ It has naked seeds as fruits around it does not develop.

A conifer is the most typical example of a gymnosperm. In the conifer life cycle, windblown pollen grains replace swimming sperm. Following fertilization,!the seed develops from the ovule, a structure that has been protected within the body of the sporophyte plant. The seeds are uncovered and dispersed by the wind.

Roots : It has well-developed tap roots. Lateral roots are longer than primaryroots.

Stem: The main stem has two types of branches called long-shoots and dwarfshoots.

Leaves: The leaves are also two types of which are foliage and scale-leaves.Foliage leaves are popularly called needles because of their shape. They are green and found only at the apices of dwarf branches. They perform the function of photosynthesis.

Scale leaves are sessile, thin and brownish. They are present on main stem as well as on both types of branches.

Cones: Cones are unisexual and called male and female-cones.

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Male cones: They arise in cluster near the ends of long shoots. They are verysmall and never longer than 2cm;Each male cone has a central axis called thalamus or torus. This axis has 60 to 100 very small scales called microsporophylls. Each microsporophyll has sac like microsporangium whichproduce small spores called microspores. These microspores develop into winged pollen grains and are liberated in air.

Female cones: They develop singly in place of dwarf-shoots. They are larger insize and measure upto 20cm in length and upto 10cm in width. Each female cone has an elongated axis (thalamus) on which large number of paired scales are present called megasporophyll having megasporangium or ovule, each ovule produce 4 comparatively large megaspores, out of these four, one will survive and develop into female gametophyte.

Gametophytes of Pinus:

Male gametophyte: Each microspore after pollination, is transferred to femalecone and undergoes a period of rest in pollen-chamber, which is inside megasporangium. During next season, microspore germinates to form reduced male-gametophyte. It consists of prothallial cell, elongated pollen-tube having tube cell, stalk cell and two sperms or male gametes.

Female gametophyte: Each functional megaspore develops into a body calledfemale gametophyte within megasporangium. Each gametophyte has two archegonia each having single ovum.

Fertilization and formation of seed: One of the male gamete fuses with theovum to form oospore, becomes diploid. It develops into an embryo. In the mean time, the whole megasporangium develops into seed. Pinus seed has seed coat, endosperm and an embryo with an axis to which 6 to 10 cotyledons are attached. The two ends of the axis have plumule and radicle. Pinus seed has epigeal germination and gives rise to pinus plant.

THUJA:

In Thuja, the female cones are small, spherical or oval in shape and about the size of a spherical fruit locally called "bair" (berry). They consist of hard brown colour scales with triangular apices.

6.4 ANGIOSPERM

More than half of the plants present on earth belong to this group. Angiospcrms are those flowering tracheophvtes which produce seeds within fruits. This is because the angiospermic flowers have ovules enclosed in the ovary. Angiospcrms are divided into two major groups monocotyledons and dicotyledons having one and two cotyledons (seed leaves), respectively.

6.4.1 Parts of Angiosperm:

The body of an angiospermic plant may be divided into two parts, namely vegetative and reproductive parts. Vegetative parts have root, stem and leaves. Reproductive parts are flower, fruit and seed. These vegetative parts andreproductive parts of angiosperm have already been discussed in chapter 2 with reference to Brassicacampestris.

In angiosperms, the reproductive structures are located in the flower, which consists of highly modified leaves.

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BiologySindh Text Book Board, Jamshoro.

6.5 MORPHOLOGICAL DIFFERENCES BETWEEN DICOT AND MONOCOT PLANTS

6.6Importance of Vascular plants:

Importance of vascular plants are:

1. Many vascular plants specially angiosperms are source of food e.g. wheat, rice, maize, pulses etc.

1. Many vegetables come from vascular plants e.g. potato, cauliflower, radish, carrots, bean, lady finger, tomato, onion etc.
2. Many ingredients of our food also come from vascular plants e.g. mustard, sugar, coconut, etc.

1. Many plants used as fodder belong to this group e.g. grasses, sorghum, burseem, jantar etc.

1. Many delicious fruits come from vascular plants e.g. Apple, mango, apricot, banana, citrus etc.

1. Timber is obtained from these plants, e.g. pinus, deodar, cedrus, sheesham, kikkar etc.

1. Many useful things are obtained from these plant, which serve as medicine e.g. Amaltas, cinchon, Ajwain etc.

1. Fibre of some plants are used in making cloth and rope such as cotton and jute.

1. Many plants are used for beautification as ornamental plant e.g. Rose, jasmine, shoe flower, glory of night etc.

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BiologySindh Text Book Board, Jamshoro.

SUMMARY

Plants may be defined as multicellular, eukaryotic, chlorophyllous living organisms having cell-wall made up of cellulose and their zygotes develop into an embryo.

Bryophytes are the simplest group of plants. They are relatively poorly

adapted to life on land, so are mainly confined to damp shady places. They are amphibious needing water for sexual reproduction.

Bryophytes show distinct heteromorphic alternation of generation. It means the two generations called gamctophyte and sporophyte are morphologically as well as cytologically different. In contrast to other plants, bryophytes have dominant gametophyte (Haploid).

Tracheophyte are the plants, which have conducting or vascular tissues. Nearly, all tracheophytes have well developed root, stem and leaves.

Ferns are the common and important group of pteridophytes. They are found growing in moist cool, shady places. The common examples of ferns are Dryopteris, Pteris, Adiantum, Marsilea etc.

Spermatophytes produce seeds. Spermatophytes are divided into two major groups called gymnosperms and angiosperms. Gyrnnosperms have naked ovules because cones are without ovaries. Ovules develop into naked seeds as fruits are absent due to the absence of ovaries.

The body of an angiospermic plant may be divided into two parts, namely vegetative and reproductive parts. Each part is subdivided into different organs.

Flower is a highly modified form of a branch, which is responsible for the reproduction of plants by producing seeds within fruits.

Book arranged by 63

BiologySindh Text Book Board, Jamshoro.

EXERCISE

1. Fill in the blanks with appropriate terms:

i)Bryophytes are one of the two groups of plants, the other being______.

ii)The dominant generation in bryophytes is ______generation.

iii)Sporophytic generation is partly or completely dependent on gametophyte in ______plants.

iv)Adiantum has spore producing bodies found at ______.

v)Gymnosperms have ______ovules.

1. Write whether the following statements are true or false:

i)Funaria has true leaves.

ii)Water is necessary for fertilization in Marchantia.

iii)The other name of Pteris is Adiantum.

iv)Dryopteris plant belongs to Musci of Bryophyta.

v)Tracheophyta have trachea in the xylem.

1. Encircle the appropriate answer:

i)The group of Marchantia is

(a) Hepaticae (b) Musci

(c) Mosses (d) Anthoceratae

ii)The group of Funaria is

(a) Hepaticae (b) Musci

(c)Anthocerotae (d) Hornwort

iii)The group of Anthoceros is

(a)Hepaticae (b) Musci

(c)Liverworts (d) Anthocerotae

iv)Typical flowers are present in the group of spermatophyte

(a)Gymnosperm (b) Angiosperm

(c)Pteropsida (d) All of them

v)Horse tails are the common name of

(a)Psilopsida (b) Lycopsida

(c) Sphenopsida (d) Pteropsida

1. Write detailed answers of the following questions:

i)What are plants? Give general characters and groups of bryophytes and tracheophytes with examples.

iii)What are the different parts of an angiospermic plant? Describe the parts of a flower in detail.

iv)Describe the characters and groups of tracheophyta.

1. Define the following terms:

1. Differentiate between:

i)Sprophyte and gametophyte.

ii)Bryophyta and tracheophyta.

iii)Antheridia.and archegonia.

iv)Angiosperms and gymnosperms.

Male and female cone.

Monocot and dicot plant.