Chapter 3 Plant Kingdom

Question 1.
What is the basis of the classification of algae?
Solution:
Classification of Algae: The algae are divided into three main classes: Chlorophyceae, Phaeophyceae, and Rhodophyceae.

1. Chlorophyceae: The members of Chlorophyceae are commonly called green algae.
2. Phaeophyceae: The members of Phaeophyceae or brown algae, are found primarily in marine habitats.
3. Rhodophyta is commonly called red algae. (See Table on the opposite page)

Question 2.
When and where does reduction division take place in the life cycle of a liverwort, a moss, a fern, a gymnosperm and an angiosperm?
Solution:
I. Liverwort – The main part of the body of liverwort is thalloid. Haploid gametes are produced from the male and female sex organs garnets fuses to form zygote. Zygote develops in the form of sporophytes. These sporophytes are further differentiated into foot, seta and capsule. As a result of reduction division many haploid spores are produced in capsule.
II. Moss – In the first stage in moss primary protonema develops into secondary ’ protonema. Both these stages are haploid. Zygote formed by the fusion of gametes further produce sporophytes.
III. Fern – Leaves of sporophyte bear sporangia in which spores are produced by reduction division in meiosis.
IV. Gymnosperm – In microsporophylls and megasporophylls that bear microsporangia and megasporangia respectively, reduction division occurs to produce microspores (pollen grains) and megaspore.
V. Angiosperm – Main part of the body is sporophytic and bears flowers. Reduction division takes place in anthers of stamen i.e. haploid pollen grains and in the ovary of pistil producing eggs.

Question 3.
Name three groups of plants that bear archegonia. Briefly describe the life cycle of any one of them.
Solution:

Archegonia is the female reproductive organ of

1. Bryophytes
2. Pteridophytes and
3. Gymnosperms groups of plants.

The life cycle of gymnosperms: The gymnosperms are heterosporous, they produce haploid microspores and megaspores. The two kinds of spores are produced within sporangia that are borne oil sporophylls which are arranged spirally along an axis to form lax or compact strobili or cones.
The strobili bearing microsporophylls and microsporangia are called microsporangia or male strobili. The microspores develop into a male gametophytic generation which is highly reduced and is confined to only a limited number of cells. This reduced gametophyte is called pollen-grain. The development of pollen- grains takes place within the microsporangia.

The cones Rearing megasporophylls with ovules or megasporangia are called microsporangia or female strobili. The male or female cones or strobili may be borne on the same tree or on different trees. The megaspore mother cell is differentiated from one of the cells of the nucellus. The nucellus is protected by envelopes and the composite structure is called an ovule.

The ovules are borne on megasporophylls which may be clustered to form the female cones. The female cones are borne on the main plant body of the sporophyte. The megaspore mother cell divides meiotically to form four megaspores. One of the megaspores enclosed within the megasporangium (nucleus) develops into a multicellular female gametophyte that bears two or more archegonia or female sex organs. The multicellular female gametophytes are also retained within megasporangium.

Three groups of plant that bear archegonia are
1. Bryophyta,
2. Pteridophyta and
3. Gymnosperm.

1. Life cycle of gymnosperms: The gymnosperms are heterosporous, they produce haploid microspores and megaspores.
2. The two kinds of spores are produced within sporangia that are borne on sporophyll which are arranged spirally along an axis to form strobili or cones.
3. The strobili bearing microsporophylls and microsporongia are called microsporangiate or male strobili.
4. The microspores develop into a male gametophytic generation which is highly reduced, and confined to only limited number of cells. The reduced gametophyte is called pollen grain.
5. The development of pollen grain takes place within microsporangia.
   The cones bearing megasporophylls with ovules or megasporangia are called macrosporangiate or female strobili.
6. The male or female cones or strobili may be borne on the same tree or different trees. The megaspore mother cell is differentiated from one of the cells of the nucellus.
7. The nucellus is protected by envelopes and the composite structure is called an ovule. The ovules are borne on megasporophylls which may be clustered to form the female cones.
8. The females cones are borne on the main plant body of the sporophyte. The megaspore mother cell divides meiotically to form four megaspore.
9. One of the megaspore enclosed within the megasporangium develops into a multicellular female gametophyte that bears 2 or more archegonia or female sex organs.
10. The multicellular female gametophyte is also remaining within megasporangium.

Question 4.
Mention the ploidy of the following: protonemal cells of a moss; primary endosperm nucleus in dicot, leaf cell of a moss; prothallus cell of a fern; gemma cell in Marchantia; Meristem cells of monocot, ovum of liverwort and zygote of a fern.
Solution:
Protonemal cells of a moss – Haploid (n) Primary endosperm nucleus in dicot – Triploid (3n)
Leaf cell of a moss – Haploid (n)
Prothallus cell of a fem – Haploid (n)
Gemma cell in Marchantia – Haploid (n) Meristem cells of monocot – Diploid (2n) Ovum of liverwort – Haploid (n)
Zygote of a fem – Diploid (2n)

Question 5.
Write a note on economic importance of algae and gymnosperms.
Solution:

1. Algae like Chlorella, Gelidium (produce agar- agar) are used as food. Many algae like diatoms (used in manufacture of glass, polish, etc), algin (used in vulcanisation, artificial fibres, etc.), are used in industry.
2. Nos toe, Anabaena, etc., are useful in increasing fertility of soil. Antibiotic chlorellin is extracted from Chlorella.
3. Many algae have harmful effect also, for example, Microcystis, Chlrococcus, Oscillatoria cause water blooms and Cephaleuros species of algae are parasitic on tea leaves and cause harm to tea industry.
4. v Alginic acid are extracted from the members Phaeophycea such as laminaria, Macrocystis and carrageenin is extracted from red algae chondris Crispos.

Economic importance of gymnosperms :

1. Gymnosperms helps in checking soil erosion.
2. Seeds of Pinns gerardiana, Gnetnm gnemon and Ginkgo biloba are eaten.
3. Conifers like Pinus longifolia, Cedrus deodara, Picea, Tsngo, etc., produce soft wood. Bark of Tsugo yields tannins for making inks, seeds and bark of Cycas are used as poultica for wounds and sores.
4. Ephedra, Gnetum, Taxus baccata, Cycles rumphii are used for medicinal purposes.

Question 6.
Both gymnosperms and angiosperms bear seeds, then why are they classified separately?
Solution:
Gymnosperms are ‘naked seeded’ plants because their seeds are not enclosed in fruit wall whereas angiosperm are ‘enclosed seeds’ as seeds (ovules) are found enclosed in the ovary wall.

Question 7.
What is heterospory? Briefly comment on its significance. Give two examples.
Solution:

1. Genera like Selaginella and Salvinia which produce two kinds of spores macro and microspores are known as heterosporous.
2. The megaspore and microspores germinate and give rise to female and male gametophytes, respectively.
3. The female gametophytes in these plants are retained on the parent sporophyte for variable periods.
4. The development of the zygotes into young embryo takes place within the female gametophytes.
5. This event is considered as an important step in evolution leading to seed habit. Heterospory is considered as the first step towards seed habit. Selaginella and Marsilea, show seed habit.

Question 8.
Explain briefly
(i) Protonema
(ii) Antheridium
(iii) Archegonium
(iv) Diplontic
(v) Sporophyll
(vi) Isogamy
Solution:
(i) Protonema: The predominant stage of moss gametophyte which directly develops from spore is known as protonema.
(ii) Antheridium: The male sex organ in bryophytes, pteridophytes and gymnosperms is called antheridium. It bears male gamete.
(iii) Archegonium : It is the female sex organ found in bryophytes, pteridophytes and gymnosperms. It bears a female gamete.
(iv) Diplontic: In the life cycle of plants when their diploid stage is dominant for long time then this is called diplontic.
(v) Sporophyll: The sporophyte bears sporangia that are subtended by leaf-like appendages called sporophylls.
(vi) Isogamy: When the gametes involved in sexual reproduction are morphologically similar then this is called isogamy. These gametes are physiologically different.

Question 9.
Differentiate between the following:-
• Red algae and brown algae
• Liverworts and moss
• Homosporous and heterosporous pteridophyte
• Syngamy and triple fusion 
Solution:

Differences between red algae and brown algae are as follows

Question 10.
How would you distinguish monocots from dicots?
Solution:
Dicots are characterized by having two cotyledons in their seeds while the monocotyledons have only one.

Question 11.
Match the following content of column I with column II
Column I Column II
(a) Chlamydomonas (i) Moss
(b) Cycas (ii) Pteridophyta
(c) Selaginella (iii) Algae
(d) Sphagnum (iv) Gymnosperm
Solution:
(a) Chlamydomonas  (iii) Algae
(b) Cycas                    (iv) Gymnosperm
(c) Selaginella            (ii) Pteridophyta
(d) Sphagnum           (i) Moss

Question 12.
Describe the important characteristics of gymnosperms.
Solution:
The seed forming vascular plants which produce seeds but no fruits are called gymnosperms. General characters of gymnosperm are as follows:

• Fertilization does not require water.
• Leaves may be of two kinds: foliage leaves and scale leaves.
• The ovules are orthotropus.
• Most primitive seed-bearing plants.
• Mostly these plants are evergreen.
• Have no ovary wall, seeds are naked.
• Exhibit polyembryony. Sexual reproduction oogamous type.
• Large, tall and woody trees.

VERY SHORT ANSWER QUESTIONS

Question 1.
Which group of plants are commonly called “Amphibians of Plant Kingdom”?
Solution:
Bryophytes

Question 2.
Which pigment does provide red colour to red algae?
Solution:
Phycoerythrin.

Question 3.
Which alga does reproduce sexually by conjugation?
Solution:
Spiro gym

Question 4.
Name the organ that fixes the Plant body of Riccia to the soil.
Solution:
Hepaticopsida.

Question 5.
Which plant group is called vascular cryptograms?
Solution:
Pteridophytes.

Question 6.
Which plant is commonly called as walking fern?
Solution:
Adiantum

Question 7.
Which group of plants produces seed but not fruits?
Solution:
Gymnosperm.

Question 8.
Which part of ovule is haploid in gymnosperm?
Solution:
Endosperm

Question 9.
What is name of megasporophyll bearing ovules of angiosperm?
Solution:
Carpel.

Question 10.
Why do gymnosperms fail to produce fruits?
Solution:
Fruits are formed from ovaries. Since the gymnosperm ovules are not enclosed inside the ovaries, they do not produce fruit.

Question 11.
Why life cycle of angiosperm is called diplontic?
Solution:
Life cycle of angiosperm is called diplontic because the diploid (sporophytic) phase is more prominent and long-lived whereas the haploid (gametophytic) phase is short-lived.

Question 12.
Which algae is known as Rolling alga?
Solution:
Volvox

Question 13.
Which are the specialized structures in selaginella which bear adventitious roots?
Solution:
Rhizophores

Question 14.
What is the number of cells and nuclei present in the embryo sac of angiosperm?
Solution:
7 cells and 8 nuclei

Question 15.
Which plant is known as a living fossil?
Solution:
Cycas

SHORT ANSWER QUESTIONS

Question 1.
What are the salient features of pteridophyte?
Solution:
Pteridophytes are vascular cryptogams i.e., plants of this group possess vascular tissue (i. e., xylem, and phloem) for the conduction of water and minerals and for the translocation of foods. They are flowerless and seedless plants.
The general characters of pteridophytes are as following.
I. Primary root is short-lived. It is replaced by adventitious roots.
II. All vegetative parts possess vascular tissues. A cambium is altogether absent. In xylem trachea are absent and in phloem companion cells are absent.
III. Pteridophytes show origin and evolution of stele {i.e., vascular tissue, pericycle, and if present the pith).
IV. Pteridophytes are characterized by having only tracheids in their xylem and only sieve tube in their phloem.
V. The main plant body is the sporophyte (diploid), usually differentiated into true roots, true stems, and true leaves. A stem is usually an underground rhizome or an erect trunk as in tree ferns. Leaves are large (megaphyllous) and variously shaped.

Question 2.
What is the Alternation of Generation?
Solution:
gametophytic and sporophytic generations alternate in the life cycle, it is called the Alter-nation of generation. Or vice versa gametophyte produces gametes and their fusion product zygote or Oospore. Oospore produces sporophyte. The sporophyte produces spores. Spores germinate and produce gametophyte.

Question 3.
What are gemmae? Name two plants that produce gemmae.
Solution:
Gemmae are green, multicellular asexual buds, which develop in small receptacles, called gemmae cups, on the thallus.
The gemmae become detached from the parent thallus and germinate to form new individuals. e.g., Marchantia, Riccia.

Question 4.
Differentiate between cytotaxonomy and chemotaxonomy.
Solution:
Cytotaxonomy that is based on cytological information like chromosome number, structure, behaviour and chemotaxonomy that uses the chemical constituents of the plant to resolve confusions, are also used by taxonomists these days.

Question 5.
Differentiate between monocotyledon and dicotyledons.
Solution:

Question 6.
Mention four types of Placentation with suitable examples.
Solution:

• Marginal placentation: Example members of the family fabaceae (Crotalaria)
• Axile placentation: Example members of the family Malvaceae (Hibiscus)
• Parietal placentation. Example: Cucumber.
• Basal placentation Example: Sunflower.

Question 7.
What are the features of Gemmae found in bryophytes?
Solution:
Gemmae are the means of asexual reproduction found in many bryophytes (ex-Liverworts). They are one to many-celled, specially produced clonal plant fragments. They are green multicellular, asexual buds which develop in small receptacles called “gemma cups” located on the thalli. Gemmae become detached from the parent body and germinate to form a new individual

Question 8.
What is the basis of the classification of the phylogenetic system?
Solution:
It indicates evolutionary as well as the genetic relationship among organism, it is based on the fossil record, biochemical, anatomical, morphological, embryological, physiological, genetics, Karyotype, and other studies.

Question 9.
What are the main features of Anthocerotopsida?
Solution:
These are also known as hornworts because typical horn-like appearances are present of their sporophyte. These contain thalloid gametophyte, distinctly dorsiventral, rhizoids are present, Thalloid do not possess air chambers and scales. Each cell of thallus has a single large chloroplast with a pyrenoid.

LONG ANSWER QUESTIONS

Question 1.
Enumerate distinguishing characters of Bryophytes.
Solution:

• Bryophytes are called “Amphibians of the plant kingdom” They grow in moist shady places. They require water for their sperms to swim towards eggs, hence the term ‘amphibians’.
• The plant body is gametophyte so that it produces garnets.
• The gametophyte is nonvascular so that xylem and phloem tissues are absent.
• The gametophyte is thalloid in structure or it may be differentiated into stem-like, root-like and leaf-like organs.
• Gametophyte reproduces sexually. The male sex organs are antheridia and the female sex organs are archegonia. Antheridia produce flagellated motile sperms. Archegonia produce female gamete or egg.
• Fertilization results in the formation of diploid oospore. It produces diploid sporophyte Sporophyte reproduces asexually and produces haploid spores. They germinate and produce haploid gametophyte. The sporophyte is dependant on the gametophyte.
• In the life cycle, there is an alternation of generation between haploid gametophyte and diploid sporophyte.
• Bryophytes also show vegetative reproduction by fragmentation, gemmae formation etc.

Question 2.
Write short notes on the following :
(a) Peristomial teeth of moss
(b) Protonema of moss
(c) Archegonia of moss
Solution:
(a) Peristomal teeth are located just below the operculum. It helps in the dispersal of spores by the hygroscopic movement of its outer ring while the inner ring does not show the hygroscopic movements.
(b) Each spore produces a filamentous juvenile stage called protonema. Protonema has two types of branches, subterranean nongreen rhizoidal, and green Mediterranean branches. Buds develop on green prostrate branches which grow to form new moss plants.
(c) Female reproductive organ of moss is called archegonium.

Question 3.
Explain the general characters of the Gymnosperm plant body. (Tumkur 2008)
Solution:

• Gymnosperm plant body is sporophyte.
• Sporophyte consists of stem, root and leaves. Stem is unbranched in cycas. the stem bears crown of leaves at the tip.
• The foliage leaves are pinnately compound in cycas and needle-like in conifers. Brown small non-photosynthetic leaves called scale leaves/cataphylls are present in cycas.
• In cycas, the cataphylls are thickly covered with brown hairs called ramenta.
• The foliage leaves are green. The pinnae are tough, leathery and has only midrib without veins.
• Young leaves show circinate vernation.
• The roots are inhabited by blue-green algae like Nostoc help the plant in nitrogen fixation
• The sporophyte produces two types of spores so it is heterosporous.

Question 4.
Give a comparative account of gymnosperms and angiosperms.
Solution:
Comparison of gymnosperms and angiosperms

Question 5.
Describe major features of Plant kingdom.
Solution:
Features of Plant Kingdom:

• Plants are autotrophic, except for some carnivorous, plants. They trap photo energy from sunlight and convert it to chemical energy through I photosynthesis. Because of this plants are the main channel for supplying energy in the food chain on earth.
• Reproduction in plants can be by any of the following modes: Vegetative or Asexual, and Sexual Reproduction.
• Plant cell is unique because of presence of cell wall and large vacuoles. Green parts of plant contain chlorophyll, which helps them in trapping the photo energy.
• Sizes of plants can vary from microscopic to a very large tree. Plants are mainly divided into Algae, Bryophytes, Pteridophytes, Gymnosperms and Angiosperms.
• Lower plants, like algae and bryophytes, have thalloid structures, while higher plants, like gymnosperms and angiosperms, have clearly defined roots and stems.
• In higher plants root gives a means to anchor in the soil and helps the plant in taking minerals and water from the soil. Green leaves on the stem help them in photosynthesis.
• Most of the plant growth as a result of photosynthesis. After photosynthesis, extra food is utilized to facilitate growth.
• Usually in higher plants growth is unlimited and some taller trees can live a life of more than 1000 years.
• Being the main carbon fixation agent, plants are very important for the whole ecology.
• The whole food basket for humans is being filled by the plant kingdom. Even animal products, like milk and poultry, are indirect results of a plant’s carbon fixation.
• Plants supply raw materials for a majority of economic activities. Wood for furniture and building materials comes from plants. The whole paper industry is dependent on the plant kingdom. Think of life if there was no paper and you may understand the larger impact on human civilization.
• Angiosperms have special organs, called flowers, to bear sexual parts. Flowers are a helpful tool in facilitating variations and further evolution of the plant kingdom.