Plant Kingdom: Algae, Bryophytes, and More

• These notes cover the plant kingdom, algae, bryophytes, pteridophytes, gymnosperms, angiosperms, and alternation of generations

Plant Kingdom

• Includes algae, bryophytes, pteridophytes, gymnosperms, and angiosperms
• Kingdom is composed of multicellular, photoautotrophic organisms
• Cell walls consist of cellulose
• Exhibit indefinite growth
• Store food mainly as starch
• Kingdom-Plantae divisions include algae, bryophytes, pteridophytes, gymnosperms, and angiosperms
• Eichler (1883) divided the plant kingdom into two sub-kingdoms based on seed presence
• Cryptogamae have hidden sex organs and lack seeds/flowers, including thallophytes, algae, bryophytes and pteridophytes
• Phanerogamae have evident sex organs with seeds, contains gymnosperms and angiosperms

Algae

• Chlorophyll-bearing, simple thalloid, autotrophic, and aquatic organisms inhabiting freshwater and marine environments
• Found on moist stones, soils, and wood
• Associate with fungi (lichens) and animals
• Algae vary in size from microscopic unicellular forms (Chlamydomonas) to colonial (Volvox), filamentous (Ulothrix, Spirogyra), and herb-like forms (Chara)
• Reproduce vegetatively, sexually, and asexually
• Algae life cycles include haplontic (Ectocarpus), diplontic (Fucus), and haplo-diplontic (Polysiphonia) types
• Algae serve as primary producers, forming the base of aquatic food cycles

Algae Divisions

• Chlorophyceae (Green algae) contain chlorophyll-a and b, store starch, have cellulose cell walls, flagella (2-8 equal apical), inhabit freshwater and brackish/salt water
• Phaeophyceae (Brown algae) contain chlorophyll-a, c and fucoxanthin, store mannitol and laminarin, their cell walls consist of cellulose and algin
• Their flagella (2 unequal lateral), inhabit freshwater (rare), brackish water and saltwater
• Rhodophyceae (Red algae) contain chlorophyll-a, d and phycoerythrin
• They store floridean starch, cell walls contain cellulose, pectin, and polysulphate esters, and they lack flagella , inhabit freshwater (some), brackish water and saltwater (most)

Important Algae

Ulothrix

• Belongs to Chlorophyceae class
• Found in freshwater; Ulothrix flacca and U. implexa are marine and lithophytic respectively
• Thallus is an unbranched filament with a basal holdfast cell, an apical cell, and rectangular cells
• Each cell has a single nucleus, band-like chloroplast with pyrenoids, central vacuole, and cellulose cell wall with pectin
• Vegetative reproduction is by fragmentation
• Asexual reproduction by zoospores under favorable conditions
• Nucleus of each cell (except holdfast) divides mitotically, forming 2-64 nuclei followed by bi- or quadriflagellate zoospores development
• During unfavorable conditions Ulothrix reproduces asexually via hypnospores, akinetes, and palmella stage
• Sexual reproduction is isogamous, involving biflagellate gametes fusion to form a zygospore
• Zygospore undergoes meiosis after a resting period to produce haploid meiozoospores that germinate into new filaments under favorable conditions
• Ulothrix has a haplontic life cycle

Batrachospermum (Frog Spawn Alga)

• Freshwater filamentous rhodophycean alga
• Filament has a branched, beaded appearance; short branches or glomeruli at nodes with long branches at some locations
• Internodes are made of single, long cells, surrounded by loose cortex
• Short lateral cells are small and elliptical
• Alga multiplies vegetatively (fragmentation/gemmae) and asexually (monospores)
• Male sex organs are called spermatangia, female sex organs are called carpogonia
• Meiosis occurs immediately after fertilization, forms a haploid carposporophyte (cystocarp) that produces carpospores
• Carpospore forms a highly branched filamentous chantransia stage (juvenile stage) and multiplies by monospores
• Adult alga grows over the chantransia stage

Economic Importance of Algae

• Used as food because algae have carbohydrates, inorganic compounds, and vitamins
• Examples include; Porphyra has 30-35% protein, 40-45% carbohydrate, vitamin-A and C
• Ulva, Alaria, Chlorella (30% carbohydrate, 30% proteins, and 15% lipid), Chondrus, and Codium
• Chlorella and Spirulina are protein-rich and used as food supplements (particularly in space travel)
• Agar-agar is a polysaccharide (agarose and agaropectin) obtained from Gelidium, Gracilaria, and Gigartina, it is used in producing processed cheese, pudding, creams, jellies, and culture media
• Carrageenan is a cell wall polysaccharide colloid from Chondrus crispus and Gigartina stellata that is used to stabilize emulsions in paints, cosmetics, alcohol, and sugar industries
• Alginate is a salt from alginic acid from Laminaria, Ascophyllum, Fucus, Macrocystis, this is useful as a thickener, emulsifier and gelling agent
• Diatomite is an insoluble, chemically inert, diatom deposit that is used as filters, insulators in boilers/furnaces, and nitroglycerine absorbents
• Laminaria and Fucus provide iodine and bromine
• Blue-green algae like Nostoc, Anabaena, Aulosira, Oscillatoria fix nitrogen
• The antibiotic chlorellin is obtained from Chlorella
• Chlorella, Chlamydomonas, Euglena, Scenedesmus, and Pyrobotrys are used in sewage disposal
• Microcystis, Chroococcus, Oscillatoria, and Anabaena cause water blooms with negative effects
• Cephaleuros sp. parasitize tea and coffee leaves

Bryophytes

• They are called amphibians of plant kingdom
• They live in soil, depends on water for sexual reproduction
• Thallus-like plant body, attached to substratum by unicellular/multicellular rhizoids
• Lack roots, stem or leaves
• Main plant body is haploid and produces gametes (gametophyte)
• Male sex organ is called antheridium, produces biflagellate antherozoids
• Female sex organ is called archegonium, produces a single egg
• An antherozoid fuses with the egg to produce a zygote
• Zygotes do not undergo reduction division immediately; produces a sporophyte (multicellular)
• Sporophyte is attached to photosynthetic gametophyte and gets nourishment
• Sporophyte produces haploid spores via meiosis, they then germinate into a gametophyte

Bryophyte Classification

• This divides the plants info three classes: Hepaticopsida (Riccia, Marchantia and Pellia) are liverworts, Anthocerotopsida (Anthoceros) are hornworts, and Bryopsida (Funaria, Sphagnum Polytrichum and Tokakia) are mosses

Liverworts

• They grow in moist and shady places, like Marchantia
• Thallus is dorsiventral, closely appressed to the substrate
• Gemmae are green, multicellular, asexual buds
• The gemma cups are present on furrows of dorsal side of Thallus
• Sporophyte is differentiated into a foot, seta and capsule, with spores produced within; spores germinate into free-living gametophytes
• Marchantia are thalloid, green, dorsiventral, dichotomously branched liverworts
• Dorsal side has a median longitudinal groove and rhomboidal or polygonal areas
• Ventral side bears scales and rhizoids; rhizoids are unicellular, colorless (smooth-walled or tuberculate)
• Sex organs are dioecious with male and female thalli
• The sex organs are borne on the gametophores, developed in receptacles
• Mature antheridium is ovoid, supported on stalk and has a jacket layer enclosing androcytes that produce biflagellate sperm
• The archegonia have a short stalk that attaches the venter to receptacle, the venter also has collar-like structure called perigynium

Mosses

• They grow under same conditions as liverworts
• The predominant life cycle stage is protonema, which develops directly from a haploid spore and is creeping, green, branched, and filamentous
• Second stage is leafy, a lateral bud develops from secondary protonema
• Mosses attach to the soil via multicellular and branched rhizoids
• Reproduction is by vegetative and sexual processes
• The sporophyte in mosses is more elaborate than in liverworts
• Common examples include Funaria, Polytrichum, and Sphagnum
• Funaria has a small yellowish green gametophore and an erect, branched or unbranched structure called axis
• The phylloids are small spirally arranged leaf like structures
• Rhizoids are multicellular, branched and have oblique cross walls
• Internally, the cells are arranged in three regions: epidermis, cortex, and central cylinder
• Vegetative reproduction takes place by fragmentation, secondary protonema formation, tubers, gemmae, bulbils (resting buds arise from protonema)
• Gametes are manufactured in the well differentiated archegonia and antheridia on the top of the same plant which is monoecious
• The main axis acts as male shoot (antheridiophore) and the lateral branch acts as a female shoot.
• Each antheridium consists of stalk and club-shaped body with jacket; it forms elongated, spirally coiled biflagellate antherozoids
• Each archegonium has flask shape, consists of short multicellular stalk
• The walls of the venter have two layers which enclose one large ovum and a Venter Canal Cell (VCC)
• Neck contains 6-9 Neck Canal Cells (NCC)
• Paraphysis a sterile structure is present between the antheridia and archegonia
• The antherozoids swim in water and are attracted to archegonium by a sugar substance

Funaria Sporophyte

• Consists of foot, seta, and capsule which obtains nutritional support from the parent gametophyte
• Capsule is differentiated into 2-3 layered lid that is cup-shaped which is the operculum
• The annulus is a ring-like layer of thickened cells at the base of the operculum
• the Peristome are 32 tooth-like projections and Apophysis the green photosynthetic region and the collumella containing water
• Stoma has single ring-like guard cell
• Spores germinate to produce a juvenile stage called filamentous protonema
• Protonema is a vegetative, transitory stage containing non-green rhizoidal branches and green prostrate branches
• Prostrate branches develop buds to form moss plants

Economic Importance of Bryophytes

• Limited economic importance, mosses serve as food for mammals, birds, and other animals
• Mosses and lichens are the first organisms to colonize rocks
• Decompose rocks and make soil for further growth of plants
• Sphagnum can be used as peat, as fuel, and as packing material for living materials due to its water-holding capacity

Pteridophytes

• The first terrestrial plants with vascular tissues (xylem and pholem), also called ferns or vascular cryptogams
• Pteridophytes are located in cool, damp, and shady habitats and thrive in sandy conditions
• In pteridophytes, the main plant body is a sporophyte; it has true roots, stem, and leaves
• Sporangia are subtended by leaf-like appendages to create sporophylls; the sporophylls can create strobili or cones in Selaginnella and Eqisetum
• Gametophytes bear male & female sex organs (antheridia and archegonia), most pteridophytes are homosporous (producing similar spores)
• Heterosporous pteridophytes (e.g. Selaginella and Salvinia produce two spore types by macro (large) and micro (small) spores meiosis
• The spores give rise to a multicellular prothallus (gametophyte) with antheridia and archegonia
• Zygote development into a young embryo occurs within the female gametophytes
• This event is a precursor to the seed habit and an important evolutionary step
• Pteridophytes could not achieve success on the terrestrial land due to requirement of wet conditions for spore germination and the susceptibility of prothallus

Pteridophyta Classification

• Four Main Classes (i) Psilopsida (e.g. Psilotum) (ii) Lycopsida (e.g. Selaginella and Lycopodium) (iii) Sphenopsida (e.g. Equisetum) (iv) Pteropsida (e.g. Dryopteris, Pteris and Adiantum)

Adiantum

• Known as maidenhair fern, the sporophytic (diploid) main body is differentiated by root, stems and leaves
• Stem is perennial, dichotomously branched, and covered with scales (paleae)
• Primary root is replaced by adventitious roots short lived
• Leaves (compound) arise alternately/spirally on rhizome; leaflets are called pinnules and veins spread in a fan-like manner
• Vegetative reproduction occurs by the rhizome and growth of adventitious buds
• Fertile leaves are known as sporophyll, and vegetative leaves can also form them
• Pinnule blade margin folds to form a false indusium, covering the sorus which are groups of sporangia
• Sori can be sub-marginal in position continuously or in the different development stage through meiotic division
• Spores are dispersed by wind after the breakdown of annulus and stomium
• Each spore forms gametophyte (prothallus) when reaching substratum
• Antheridia and archegonia are also present on ventral side
• Archegonia occur behind the apical notch in (apical cushion)
• The archegonium had walls in two layers enclosing a large ovum and a small canal cell lying above the ovum
• Antheridium that scattered the rhizoids are sessile and hemispherical
• Protandry and Thin water allow sperms to swim towards archegonia(chemotaxis)
• Known as the waling fern because of its ability to use water an soil

Dryopteris (Fern)

• Commonly known as fern, the sporophytic main plant body (2n) has underground stems and well-developed shoot system
• Leaves (fronds) appear as tightly coiled in early stages
• Vegetative reproduction is accomplished by adventitious buds, rhizome fragmentation, and spores growth which occurs via ventral surface on leaves
• Sporophytes bear sporophylls producing spores that grows towards gametophyte
• Gametophytes need water for reproduction
• The spores are called microspores and the development is known as heterspory

Gymnosperms

• Ovules not enclosed by an ovary wall
• Seeds develop post-fertilization and are not covered
• Gymnosperm size ranges; medium-sized trees, tall trees and shrubs
• They generally have taproots
• Some (Pinus exhibit mycorrhiza
• Some (Cycas) exhibit small specialized roots called coralloid roots, associate with N2-fixing cyanobacteria
• Fertilization occurs by siphonogamy, the stems are either branched (Cycas) or unbranched (Pinus and Cedrus)
• Leaves are simple or compound; conifers have reduced surfaces

Gymnosperm Classification

• Chamberlain (1934) divided gymnosperms into two classes, i.e. Cycadophyta and Coniferophyta
• Class-Cycadophyta includes both living and extinct forms, e.g. Cycadeoidea, Lyginopteris (extinct), Cycas and Zamia
• Class-Coniferophyta also includes both extinct and living species, e.g. Cordaites, Ginkgo biloba, Pinus, Gnetum and Ephedra

Cycas (Living Fossil)

• Cycas shows resemblances to extinct pteridosperms and cycads
• The cycas main plant body (sporophytic, evergreen) has true roots, stems, and leaves
• Roots arise from the lower stem and include primary/tap and coralloid roots
• The dichotomously branched, apogeotropic, and bluish green coralloid roots are inhabited by blue-green algae to assist with fixing nitrogen
• The stem is thick, cylindrical, columnar, aerial and unbranched. Older parts remain covered in persistent, woody leaf bases, conjoint, collateral, and open vascular bundles
• At the base of the stem, bulbils are present at its base, and the wood has dimorphism

Pinnus Tree

• Mature individual has large differentiated trees and thick columnnar Stems
• Main truck is cylindrical and branches are limited to the the upper parts the stem
• In the axil of the scale leaves contain the paired scales
• Pollination is anemophilous the distal broader scale that contains the ovuliferous is called apohysis
• Pinnus are a source of commercial products like timbers and resins

Angiosperms

• Seeds are enclosed by fruits
• Pollen grains and ovules develop in flowers
• The largest plant group (12,500 genera and 250,000 species) that occupy ecological habitats
• Size varies from small (Wolffia) to tall trees like Eucalyptus
• Plant body is sporophytic and distinguished by true stem root and leaves
• Vascular bundles have consist of xylem and pholem
• The Male sex organ in a flower is stamen
• Pistil has the ovary that contain ovules; and the embryo sac is from gametophytes
• Pollen is released from tissue style; One male gamete fuses with two synergids and antipodals
• Angiosperms produce economic products

Angiosperm Classification

• It describes the superficial system by morphology that are artificial
• Phylogenetic classification that is acceptable; using all the features
• According to Bentham the system is helpful for classification and natural purposes
• According to this system which diverges from trees the ancestral habit is maintained; one is retained

Alternation of Generations

• Occurs during the life cycle of any sexually reproducing plant. There is alternating generation of gametes produce spores.
• The haploids are produced from mitotic, and creates the zygote; some algae like volvox
• Sporophyte is the dominant and photosynthetic phase of the plant
• Occurs in all seed bearing plants
• Bryophytes exhibit that are intermediate; pteridophytes exhibit by their dominate phases

Explore the plant kingdom, including algae, bryophytes, pteridophytes, gymnosperms, and angiosperms. Understand their characteristics, divisions, and life cycles. Learn about the differences between cryptogamae and phanerogamae.