Notes-Class-11-Science-Biology-Chapter-3-Kingdom Plantae-Maharashtra Board

Differences between sub-kingdoms Cryptogamae and Phanerogamae :

Accessory pigments of algae :

Various types of photosynthetic pigments are found in algae.

• Chlorophyll-a (Essential photosynthetic pigment) is present in all groups of algae.
• The accessory pigments are chlorophyll-b, chlorophyll-c, chlorophyll-d, carotenes, xanthophylls and phycobilins. Phycobilins are of two types, i.e. phycocyanin and phycoerythrin.

Green algae with their characteristic shapes of chloroplast:

• Chlamydomorzas – Cup-shaped
• Spirogyra - Spiral or ribbon shaped
• Oedogonium - Reticulate
• Zygnema - Stellate or Star-shaped

Forms of green algae:

• Unicellular motile: e.g. Chlamydomonas
• Unicellular non-motile: E. g. Chlorella
• Colonial fonns: e.g. Volvox
• Filamentous branched: e.g. Cladophora, Chara
• Filamentous unbranched: e. g. Ulothrix, Spirogyra

Reproduction in Phaeophyceae :

• Vegetative reproduction takes place by fragmentation.
• Asexual reproduction takes place by biflagellate zoospores.
• Sexual reproduction: Isogamous, anisogamous or oogamous
• The gametes are pyriform (pear shaped) and flagellated.

Differentiate between Chlorophyceae and Phaeophyceae :

Reproduction in Rhodophyceae :

• Vegetative reproduction occurs by fragmentation.
• Asexual reproduction occurs by non-motile spores.
• Sexual reproduction takes place by non-motile gametes, oogamous and accompanied by complex post fertilization developments.

Importance of algae :

• Many species of algae are used as food. For e.g. Chlorella (rich in cell proteins hence sed as food supplement even by space travelers), Sargassum, Lammarla, Porphyra, etc.
• Alginic acid is produced commercially from Kelps.
• Hydrocolloids like algin and carrageen are obtained from brown algae and red algae respectively.
• ‘Agar’ which is used as solidifying agent in tissue culture is obtained from red algae like Gelidium and Gracilaria.
• Brown algae like sea weeds are used a fodder for sheep, goat, etc.
• Being photosynthetic, algae help in increasing the level of dissolved oxygen in their immediate environment.
• Algae are primary producers of energy rich compounds which forms the basis of food cycles in aquatic animals.

Characteristics of Bryophyta :

• Mostly terrestrial, occurs on moist and shady places.
• Non-motile forms present, except male gametes.
• It shows root like structures i.e. rhizoids and absence of vascular tissue.
• Rhizoids are unicellular in liverworts while multicellular in mosses.
• Rhizoids absorb water and minerals and also help in fixation of thallus on the substratum.

Life cycle of Bryophyta :

• Life cycle of Bryophytes shows sporophytic and gametophytic stages.
• They alternate with each other to complete their life cycle.
• Gametophyte is haploid, thalloid or leafy and dominant. (photosynthetic, independent thalloid or erect phase)
• Sporophyte is short lived, multicellular and depends totally or partially on gametophyte for nutrition and anchorage.

Reproduction in liverworts :

• In liverworts, asexual reproduction occurs by fragmentation of thalli or with the help of specialized snuctures called as gemmae.
• These are green, multiccllular, asexual buds which grow in receptacles called gemma cup located on thalli.
• These gemmae detach from the thallus and germinate to form new individual.

Economic importance of Bryophytes:

• Some mosses provide food for herbivorous mammals, birds, etc.
• Species of Sphagnum, a moss; provides peat used as fuel.
• Mosses are also used as packing material for transport of living materials because they have significant water holding capacity.
• Mosses along with lichens are the first living beings to grow on rocks. They decompose rocks to form soil and make them suitable for growth of higher plants. .
• Dense layers of mosses help in prevention of soil erosion, thus act as soil binders.

Characteristics : Pteridophytes are known as first vascular and true land plants :

• Habitat : Ptendophytes grow in moist and shady places. e.g. Ferns, Horsetail. Some are aquatic (Azolla, Marsilea), xerophytic (Equisetum) and epiphytic (Lycopodium).
• Plant body: It is differentiated into root, stem and leaves.
• Primary root: The primary root is short lived and is soon replaced by adventitious roots.
• Stem: The stem may be aerial or underground. .
• Leaves: This group contains plants with pinnate (feather - like) leaves. Leaves may be scaly (e.g. Equisetum), simple and sessile (e.g. Lycopodium), small (microphylls e.g. Selaginella) or large (macrophylls) and pinnately compound (e.g. Nephrolepis / Ferns).
• Vascular tissues: In these members xylem consists of only tracheids and phloem consists of only sieve cells.
• Secondary growth: Secondary growth is not seen in pteridophytes due to absence of cambium.
• Alternation of generations: Pteriodphytes show heteromorphic alternation of generations in which the sporophyte is diploid, dominant, autotrophic and independent. Gametophyte is haploid multicellular, generally autotrophic and short lived.

Reproduction in Pteridophytes:

• Sporophyte: The sporophyte shows asexual reproduction and produces spores by meiosis from which the gametophyte develops.
• Gametophyte: The gametophyte is haploid, recessive but independent and reproduce sexually. The product of sexual reproduction, i.e. zygote produces diploid sporophyte.
• Spores: The plants are heterosporous (producing different types of spores), small microspores and large megaspores, while many are homosporous producing only one type of spore. Spores are produced in special multicellular structures called sporangia.

Other than normal modes of reproduction, Pteridophytes show the following methods of reproduction :

• Apogamy: It is the development of the sporophyte without the fusion of male and female gametes. It arises directly from the gametophyte. Here, the sporophyte is haploid.
• Apospory: It is the development of the gametophyte from any cell of the sporophyte other than the spores. Such gametophyte is diploid in nature.

Distinguish between Bryophyta and Pteridophyta :

General characters of Gymnosperms:

• Types: Most of the gymnosperms are evergreen, shrubs or woody trees.
• Vascular tissues: They are vascular plants having xylem with tracheids and phloem with sieve cells.
• Flower: These are primitive group of flowering plants producing naked seeds. Seeds are not covered by fruit i.e. ovary.
• Body: The plant body is sporophyte. It is differentiated into root, stem and leaves.
• Roots: The root system is tap root type. In some gymnosperms, the roots form symbiotic association with other life forms. Coralloid roots of Cycas show association with blue green algae and roots of Pinus show association with endophytic fungi called mycorrhizae.
• Stem: In gymnosperms, stem is mostly erect, aerial, solid and cylindrical. Secondary growth is seen in Gymnosperms due to the presence of cambium. In Cycas it is usually unbranched, while in conifers it is branched. (e.g. Pinus, Cedrus).
• Leaves: The leaves are dimorphic. The foliage leaves are green, simple needle like or pinnately compound, whereas scale leaves are small, membranous and brown.
• Spores: Spores are produced by microsporophyll (Male) and megasporophyll (Female). Gymnosperms are heterosporous. The microsporophylls and megasporophylls are usually arranged in compact structures called cones or strobili.
• The microsporangium (pollen sac) produces large number of spores (microspores or pollen grains) which are light in weight.
• Each megasporangium (ovule) is surrounded by integuments. The ovule is orthotropous, i.e. upright.
• Vegetative reproduction: Vegetative reproduction takes place with the help of bulbils.
• Sexual reproduction: The pollination in Gymnosperms ts anemophilous (wind pollination) and direct as the pollen grains are received directly in the pollen chamber of the ovule.
• Fertilization occurs through a pollen tube. This process is called siphonogamy.

• Alternation of generation: Gymnosperms show a distinct heteromorphic alternation of generations.
• The sporophyte is diploid, dominant, autotrophic, independent. While gametophyte is haploid, recessive and dependent.
• Smallest gymnosperm : Zamia pygmaea

Economic importance –

• Cycas is grown as ornamental plant.
• Pinus is used as source of pine wood, turpentine oil and pine resin.

Angiosperms (Angios : enclosed : vessel, Sperma : seed):

Salient features of angiosperms:

• Habitat: Angiosperms is a group of highly evolved plants, primarily adapted to terrestrial habitat.
• Alternation of generations: Angiosperms show heteromorphic alternation of generation in which the sporophyte is diploid, dominant, autotrophic and independent. The gametophytes (male or female) are recessive, haploid and dependent on the sporophyte.
• Spores and Sporophylls: Angiosperms are heterosporous. Microspores (commonly called pollens) are formed in microsporangia (or anthers). They develop in highly specialized microsporophyll or stamens while megaspores are formed in megasporangia (or ovules) borne on highly specialized megasporophyll called carpel.
• Flower: Besides the essential whorls of microsporophylls (androecium) and megasporophylls (gynoecium), there are accessory whorls namely, calyx (sepals) and corolla (petals) arranged together to form flowers.
• Body: The body of sporophyte is divisible into root, stem and leaves. It has flowers, fruits and seeds.
• Vascular tissues: Vascular tissues are well differentiated. Xylem shows vessels or tracheids, while phloem shows sieve tubes and companion cells.
• Pollination: The pollination is indirect and maybe self or cross.
• Sexual reproduction: There is typically double fertilization, one male gamete fusing with egg cell to form embryo and another fusing with secondary nucleus to form endosperm.
• The zygote continues to develop within the ovule until seed is developed. The ovary simultaneously ripens into a fruit.

Two classes of Angiosperms : Dicotyledonae and Monocotyledonae.

Dicotyledonae :

• These plants have two cotyledons in their embryo.
• They have a tap root system and the stem is branched.
• Leaves show reticulate venation.
• Flowers show tetramerous or pentamerous symmetry.
• Vascular bundles are conjoint, collateral and open type.
• Cambium is present between xylem and phloem for secondary growth
• In dicots, secondary growth is commonly found.
• e.g. Helianthus annuus (Sunflower).

Monocotyledonae :

• These plants have single cotyledon in their embryo.
• They have adventitious root system and stem is rarely branched.
• Leaves generally have sheathing leaf base and parallel venation.
• Flowers show trimerous symmetry.
• The vascular bundles are conjoint, collateral and closed type.
• Cambium is absent between xylem and phloem. Therefore in Monocots, except few plants secondary growth is absent.
• e.g. Zea mays (Maize).

Monocot leaves : Canna, Grass

Dicot leaves : Hibiscus, Peepal, and Tulsi.

Noticeable differences between Gymnosperms and Angiosperms :

Various groups of vascular plants :

There are 3 groups of vascular plants:

• Pteridophytes : Pteridophytes are the only cryptogams with vascular tissue.
• Gymnosperms : Gymnosperms are the plants which possess naked seeds and also known as phanerogams without ovary.
• Angiosperms : Angiosperms are the flowering plants in which the seeds remain enclosed within the fruits. Double fertilization is the unique feature of angiosperms.

Haplontic life cycle :

• In haplontic life cycle mitosis occurs in haploid cells.
• It results in the formation of a single celled haploid or a multicellular haploid organism.
• These forms produce the gametes through mitosis.
• Zygote is formed after fertilization. This cell is the only diploid cell in the entire life cycle of the organism.
• Thus, the same zygotic cell later undergoes meiosis.
• This type of life cycle observed in some algae and fungi.
• Haplontic life cycle is observed in many algae.

Diplontic life cycle :

• Here, mitotic division occurs only in diploid cells.
• Gametes formed through meiosis are haploid in nature.
• The diploid zygote formed after fertilization divides mitotically.
• In this process, production of multicellular diploid organism or the production of many diploid single Cells takes place.
• Animals show diplontic life cycle.
• Diplontic type of life cycle is commonly observed in animals and all seed-bearing plants i.e. gymnosperms and angiosperms.

Haplo-diplontic life cycle :

• In haplo-diplontic life cycle, mitosis occur in both diploid and haploid cells.
• These organisms undergo through a phase in which they are multicellular and haploid (the gametophyte), and a phase in which they are multicellular and diploid (the sporophyte).
• It is observed in land plants and in many algae.
• It is commonly observed in bryophytes and pteridophytes.

MAP :