Plus One Botany Notes Chapter 2 Plant Kingdom is part of Plus One Botany Notes. Here we have given Kerala Plus One Botany Notes Chapter 2 Plant Kingdom.
|Text Book||NCERT Based|
|Chapter Name||Plant Kingdom|
|Category||Kerala Plus One|
Kerala Plus One Botany Notes Chapter 2 Plant Kingdom
The Kingdom Plantae of R. H. Whittaker is popularly known as plant kingdom.The plant kingdom has changed over time.
Types of Classification System
- Artificial System of Classification
Classification based on few morphological characters like habit, colour, number and shapes of leaves, etc. This system was introduced by Carolus Linnaeus.
- Natural System of Classification
This classification is based on the natural affinities among organisms. External features and internal features like anatomy, embryology and phytochemistry are considered for the classification. George Bentham and J. D. Hooker’s Classification.
- Phylogenetic System of Classification
Classification based on evolutionary relationships between organisms.
Types of taxonamies
For the suitability in studies various categorisation has been done in taxonomy. The important taxonomies are the following.
- Numerical Taxonomy.
Number and codes are assigned to each character and the data is processed in computers. This type of classification is called numerical taxonomy.
The classification of organism based on cytological information especially the number, structure, and shape of chromosomes.
The classification is based on chemical constituents present in the organism. The plant kingdom includes Algae, Bryophytes, Pteridophytes, Gymosperms, and Angio- sperms.
Algae are chlorophyll bearing simple thalloid organisms. They are usually aquatic. The algae include unicellular, colonial, filamentous or large and multicellular organisms. Vascular tissue is absent. They reproduce vegetatively asexually and sexually. Vegetative reproduction is through fragmentation. Each fragment develops into a thallus. Asexual reproduction is by the production of different types of spores, the most common being the zoospores. They are flagellated (motile) and on germination gives rise to new plants.
Sexual reproduction takes place through fusion of two gametes. These gametes can be flagellated and similar in size (as in Chlamydomonas) or non-flagellated (non-motile) but similar in size (as in Spirogyra). Such reproduction is called isogamous. Fusion of two gametes dissimilar in size, as in some species of chlamydomonas is termed as anisogamous. Fusion between one large, non-motile (static) female gamete and a smaller, motile male gamete is termed oogamous, e.g., Volvox, Fucus.
Economic Importance of Algae
- They are the major producers and fix about 50% CO2 on earth.
- They are giving food to animals.
- Many species like Porphyra, Laminaria, Sargassum are edible.
- A jelly like substance agar is obtained from Graqilaria and Gelidium. It is used commercially in ice creams and jelly.
- Algin is obtained from brown algae like Laminaria Fucus etc. It is used in various industries like pharmaceuticals.
- Carrageen is obtained from red algae. It is used in food and pharmaceutical industry.
- The unicellular algae, Chlorella and Spirulina are used for producing proteins. So it is used by space travellers as a food supplement.
Classification of algae
Algae are divided into various classes based on pigmentation, stored food and flagellation. The main classes are the following.
It is commonly called green algae. It may be unicellular, colonial or filamentous. Main pigments are chlorophyll ‘a’ and ‘b’. The chloroplasts may be discoid, plate like, cup-shaped, spiral or ribbon shaped, eg., chlamydomonas, volvox, spirogyra, chara, etc
Cell wall has inner layer of cellulose and outer layer of pectose. Reserve food is starch. Most members have pyrenoids (starch + protein).Reproduction usually take place asexual reproduction through zoospores and sexual reproduction through isogamy, anisogamy or oogamy. Zoospores are have two terminal equal
It is commonly called brown algae. Habitat is usually marine. They may be simple branched filamentous or profusely branched. The pigments are chlorophyll ‘a’, ‘c’ and fucoxanthin.Cellulose cell wall is covered by gelantinouscoating of algin. The reserve food materiaismannitol and laminarin. Plant body is divided
into holdfast, stipe and frond. Reproduction can take place, asexually by zoospore and sexually by isogamy, anisogamy or oogamy. Zoospores are pear shaped and have two un equal lateral flagella.
eg., ectocarpus, fucus, Iamìnaria,dictyota, sargassum etc.
It is commonly called red algae. The pigments are chlorophyll ‘a’, ‘d’ and r-phycoerythrin. Majority of them are marine and found on surface as well as great depths in oceans. Reserve food material is floridean starch. Cell wall inner cellulose and outer polysulphate esters. Asexual reproduction through non-motile spores and sexual reproduction through oogamy.eg., polysiphonia, porphyra, gelidium, gracilaria etc.
- Bryophytes include the various mosses and liverworts that are found commonly growing in moist shaded areas in the hills.
- Bryophytes are known as the amphibians of the plant kingdom because these plants can live in soil but are dependent on water for sexual reproduction. They usually occur in damp, humid and shaded localities.
- They play an important role in plant succession on bare rocks/soil.
- The main plant body of the bryophyte is haploid. It produces gametes, hence is called a gametophyte.
- The sex organs in bryophytes are multicellular. The male sex organ is called antheridium. They produce biflagellate antherozoids. The female sex organ called archegonium is flask shaped and produces a single egg.
- An antherozoid fuses with the egg to produce the zygote. Zygotes do not undergo reduction division immediately. They produce a multicellular body called a sporophyte.
- Some cells of the sporophyte undergo reduction division (meiosis) to produce haploid spores. These spores germinate to produce gametophyte.
Economic Importance of bryophytes
- A species of Sphagnum, a moss provide peat and used as a fuel and also used for packing material for transshipment of living materials. It has water holding capacity.
- Mosses along with lichens are the first colonisers on a rock. It has great role in ecological succession.
- Some mosses provide food for herbaceous mammals, birds and other animals.
- Mosses from the dense mats on the soil, they reduce the impact of falling rain and prevent soil erosion.
- Marchanita has medicinal properties to cure lungs and liver infections. It also has antitumour properties.
The bryophytes are divided into liverworts and mosses.
|Grow usually in moist, shady habitats such as banks of streams, marshy ground, damp soil, bark of trees and deep in the woods||Grow in dense mats over moist shady places, especially during rains. Some of them grow in desert bogs and streams|
|Plant body is thailoid in nature, i.e., they have flat, green, lobed or forked thalli attached to the ground by rhizoids||Plant consists of an erect stem-like structure, attached to the substratum by root-like rhizoids|
|Asexual reproduction takes place through fragmentation or through gemmae formation||Asexual reproduction is through fragmentation or budding in the secondary protonema|
|Sporophyte is differentiated in foot, seta and capsule||It is not differentiated in foot, seta and capsule|
|Sex organs are produced either on the same thallus or on different thalli||Sex organs are produced at the apex of the leafy shoots.|
|Capsule often posesses elasters. e.g., Marchantia||Elasters are absent e.g., Funaria, Sphagnum|
- Pteridophytes include horsetails and ferns.
- They are the first terrestrial plants which posses vascular tissues xylem and phloem.
- Pteridophytes are found in cool, damp, shady places though some may flourish well in sandy-soil conditions.
- In pteridophytes sporophyte is the main plant body. The plant body is differentiated into stem, root and leaves.
- The sporangia may be found on the lower surface of leaves called sporophylls or in distinct compact like structure called strobilus or cone.
- The spores are formed inside the sporangia. The spores germinate and develop into haploid green photosynthetic thalloid gametophyte. The gametophyte is called prothallus. The gametophyte consists of anthredia and archegonia produce antherozoid and egg respectively.
- The zygote thereafter produces a multicellular well-differentiated sporophyte which is the dominant phase of the pteridophytes. In majority of the pteridophytes all the spores are of similar kinds, such plants are called homosporous.
- Some of the sporophyte will produce dissimiar spores and are called heterosporous (Selaginella and Salvinia).
- In some members the embryo will developed from the zygote on the sporophytic plant after fertilization. It is called seed habit.
Pteridophytes are divided into 4 classes,
- Psilopsida (Psilotum)
- Lycopsida (Selaginella, Lycopodium)
- Sphenopsida (Equisetum)
- Pteropsida (dryopteris, Pteris, Adiantum)
|These are non-vascular plants||These are vascular plants|
|The main plant body is gamatophyte||It is sporophyte|
|Sporophyte is parasitic over gamatophyte||Sporophyte is independent of gamatophyte|
|Plant body can be thallus or foliose||It is differentiated into stem, leaves and roots|
|True stems and leaves are not present||It has true stem and leaves|
|Roots are absent, rhizoids are present||Roots are present|
|Sex organs are stalked||Sex organs are sessile|
- Gymnosperms are usually trees. A few are shrubs and climbers. Flowers are absent.
- The gymnosperms (gymnos : naked, sperma : seeds) are plants in which the ovules are not enclosed by any ovary wall and remain exposed, both before and after fertilisation ,
- The dominat plant body is sporophyte.The plant body consists of root, stem and leaves.
- In Pinus mycorrhiza is seen on roots. It is the association fungi on roots and helps in mineral absorption and water absorption.
- In Cycas coralloid roots are seen. Cyanobacteria like Nostoc and Anabaena are seen inside this root.
- The leaves in gymnosperms are well-adapted to withstand extremes of temperature, humidity and wind. In conifers, the needle like leaves reduce the surface area. Their thick cutide and sunken stomata also help to reduce water loss.
- The gymnosperms are heterosporous; they produce haploid microspores and megaspores.
- The two kinds of spores are produced within sporangia that are borne on sporophylls which are arranged spirally along an axis to form lax or compact strobili or cones.
- The strobili bearing microsporangia are called microsporangiate or male strobili, bearing megasporophylls with ovules or megasporangia are called macrosporangiate or female strobili.
- The plant may be monoecius (The male or female cones or strobili may be borne on the same tree) in pinus and dioecious (The male or female cones or strobili may be borne on the different tree) in cycas.
- The ovules are borne on megasporophylls which may be clustered to form the female cones. The megaspore mother cell divides meiotically to form four megaspores.
- One of the megaspores enclosed within the megasporangium (nucellus) develops into a multicellular female gametophyte that bears two or more archegonia or female sex organs. The multicellular female gametophyte is also retained within megasporangium.
- The angiosperms are flowering plants seed is covered by fruit wall. The plants may be herbs, shrubs or trees.
- The plant body is a sporophyte and it consists of root stem and leaves. Smallest angio- sperm is Wolfia and the largest is Eucalyptus.
- The angiosperms are classified into two classes, monocotyledons (only one cotyledons in their seeds) and dicotyledons (two cotyledons in their seeds).
|They contain one cotyledon||They contain two cotyledons|
|Leaves have parallel venation||Leaves have reticulate venation|
|Fibrous root system is present||Tap root system is present|
|Stomata are dumb-bell shaped||Stomata are kidneyshaped|
|Vascular bundles are scattered||Vascular bundles are arranged in rings|
|Secondary growth is absent in roots and stem with some exception||Secondary growth occurs in roots and stem|
|Roots has pith in its centre||Root is generally devoid of pith|
|Cambium is absent||Combium is present|
- Male reproductive structure called stamen
and female reproductive structure cailed pistil or carpels.
- A stamen consists of an anther and filament. A number of pollen grains are produced inside the anther. The male gamete is produced in pollen grains.
- The pistil consists of stigma style and ovary. Ovary consists of one or many ovules. The female gametophyte called embryosac and is formed inside the ovule.
- The embryo sac consists of an egg apparatus (one egg cell and two synergids), three antipodal and two polar nuclei. The polar nuclei fuse to produce a secondary nucleus.
- Pollen grains are liberated from the another and reach to the stigma of pistil through various agents called pollination. The pollen grain germinates in the pistil and two male gametes are produced.
- Pollen tube enters into the embryosac and one male gamete fuses with egg and diploid zygote is formed. It is called syngamy.
- The other male gamete fuses with diploid secondary nucleus and a triploid primary endosperm nucleus (PEN) is formed.
- The two fusions are called double fertilization. Zygote develops into embryo and endosperm nucleus develops into endosperm. The ovule develops into seed. The ovary wall develops into fruit.
The life cycle of an angiosperm is shown in below.
Differences between Gymnosperms and Angiosperms
|Vessels or trachea is absent in xylem||Trachea is present in xylem|
|Phloem contains sieve cells||Phloem tissue contains sieve tube and companion cells|
|Sporophyll are aggregated to form cones||Sporophyll are aggregated to produce flowers|
|Sepals and petals absent||Sepals and petals present|
|Cones are generally unisexual||Flowers are generally bisexual|
|Microsporophyll are woody and there is no rolling of megasporophylls||Microsporophyll are softer and rolled into ovary, style and stigma|
|Single fertilisation||Double fertilisation|
|Endosperm is haploid and formed before fertilisation||Endosperm is triploid and formed after fertilisation|
|Ovules are exposed||Ovules are enclosed in ovary|
|Pollen enters micropyle directly||Pollen germinates on stigma, pollen tube passes through style to enter ovary|
|Seed exposed because there in no ovary, so no fruit formation||Seed are enclosed in a fruit which forms after fertilisation|
Plant life cycles and alternation of generation
- Life cycles of an organism is a sequence of event that occur from birth to death of an organism.
- In plants, both haploid and diploid cells can divide by mitosis. This features leads to the formation of different plant bodies haploid and diploid.The haploid plant body represents a game- tophyte.
- After fertilisation, zygote also divides by mitosis to produce a diploid sporophytic plant body.
- Haploid spores are produced by this plant body by meiosis. These inturn, divide by mitosis to form a haploid plant body once again.
- Thus, during the iife cycle of any sexually reproducing plant, there is an alternation of generation between gamate producing haploid gametophyte and spore producing diploid sporophyte.
However, different plant groups, as well as individuals representing them, differ in the following patterns.
i. Haplontic life cycle
Sporophytic generation is represented only by the one-celled zygote. There are no free-living sporophytes. Meiosis in the zygote results in the formation of haploid spores. The haploid spores divide mitotically and form the gametophyte. The dominant, photosynthetic phase in such plants is the free-living gametophyte. This kind of life cycle is termed as haplontic. Many algae such as Volvox, Spirogyra and some species of Chlamydomomas represent this pattern.
ii. Diplontic life cycle
In this type lifecycle the diploid sporophyte is the dominant, photosynthetic, independent phase of the plant. The gametophytic phase is represented by the single to few-celled haploid gametophyte. This kind of lifecycle is termed as diplontic. All seed-bearing plants i.e., gym nosperms and angiosperms, follow this pattern.
iii. Haplo diplontic life cycle
In this type, there are two distinct multicellular phases, diploid sporophyte and haploid gametophyte are present. Both phases are multicellular. However, they differ in their dominant phases.
- A dominant, independent photosynthetic, thalloid or erect phase is represented by a haploid gametophyte. It alternates with the short lived multicellular sporophyte totally, partially or dependent on the gametophyte for its anchorage and nutrition. All bryophytes represent this pattern.
- The diploid saprophyte is represent by a dominant independent photosynthetic vascular plant body. It alternates with multicellular saprophytic independent but short lived haploid gametophyte. This pattern is called haplodiplonic life cycle. All pteridophytes demonstrate this pattern. Most algal genera are haplontic, some of them such as Ectocarpus. Polysiphonia, kelps are haplodiplontic. Fucus, an alga is diplontic.
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