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bryophytes and pteridophytes.ppt cryptogams

This document discusses cryptogams, which are early non-vascular land plants. It presents the hypothesis that all plants evolved from ancient green algae based on shared traits like chloroplasts, cellulose cell walls, and starch storage. Bryophytes like mosses, liverworts, and hornworts are described as the first land plants, lacking true roots and vascular tissue. Their life cycles involve a dominant haploid gametophyte phase and a dependent diploid sporophyte phase. Classification systems for different bryophyte groups are also outlined. Pteridophytes represent the next stage of land plant evolution with differentiated roots, stems, and leaves, but lacking seeds.

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BIO 210- Cryptogams: Bryophytes and Pteridopytes Acquatic (Algae) to Terrestrial habitat (land plants) • Hypothesis in Botany that all plants evolved from a common ancestor, ancient green algae. What account for this hypothesis? • Modern green algae share many biochemical and metabolic traits with modern plants as ff: • -Green algae and plants contain chlorophyll a and b and accessory pigments, xanthophylls (yellow pigments) and carotenes (orange pigments) and carry out photosynthesis
Con’d • -Both have cellulose as major component of cell wall • -Stores excess carbohydrates as starch, • -Plants and some green algae form cell plate during cytokinesis in mitotic cell division • Ultrastructural and molecular data on DNA and RNA sequences provide evidence that plants may have descended from a group of ancient green algae called charophytes.
Bryophytes • Bryophytes are early living nonvascular plants which include the mosses, liverworts and hornworts. • May have evolved from green algae Characteristics • They lack vascular tissues, true roots, stem and leaves. • Have cuticle; multicellular gametangia; stomata (Advancements over algae) • Habitat - Require moist environment; some are tolerant of dry areas (need moisture for active growth and sexual reproduction) • Exhibits alternation of generations: Gametophyte is haploid but dominant and conspicuous, sporophyte is diploid and dependent on the gametophyte.
• Dioicous bryophytes produce only antheridia (sperm producing structures) or archegonia (egg producing structures) on a single plant body. • Monoicous/autoicous bryophytes produce both antheridia and archegonia on the same plant body.
The Linnaeus system of Classification Kingdom Division Class Order Family Genus Species
Con’d • Kingdom: Plantae • Division: Bryophyta • 1. Class: Hepaticopsida (liverworts) • Orders: Marchantiales, Jungermanniales, Sphaerocarpales • 2. Class: Anthocerotopsida (hornworts) • Order: Anthocerotales • 3. Class: Bryopsida (Musci) • Orders: Funariales, Andreales, Bryales, Dicranales, Eubryales, Sphagnales
Characteristics of Hepaticopsida: • The liverworts grow usually in moist, shady habitats such as banks of streams, marshy ground, damp soil, bark of trees and on wood logs. • The plant body of a liverwort is thalloid or made of thalli (sing. thallus) which show dichotomous branching • Eg., Marchantia: The thallus is dorsoventrally flattened and closely appressed to the substrate. • The thallus shows differentiation into two layers: an upper photosynthetic or assimilatory region and a lower storage region with a well defined epidermis bearing air channels.
Cont’d • It has tiny cup like structures called gemmae cups bearing gemmae which are used for asexual reproduction. • Multicellular purple colored scales and unicellular rhizoids are present on the ventral surface of the thallus. • Antheridia and archegonia are present on special erect gametophores called antheridiophores and archegoniophores respectively born on separate thalli. Hence they are heterothallic
Structure of gametophyte of Marchantia polymorpha
Male thalli
Female thalli
Reproduction • Asexual reproduction in liverworts takes place by: 1 Fragmentation of thalli, 2. Gemmae (sing. gemma). Gemmae are green, multicellular, asexual buds, which develop in small receptacles called gemma cups located on the thalli. The gemmae become detached from the parent body and germinate under favourable condition.
Sexual reproduction • During sexual reproduction, male and female sex organs are produced on different thalli. The sporophyte is differentiated into a foot, seta and capsule. After meiosis, spores are produced within the capsule. These haploid spores germinate to form free-living gametophytes (male/female) • Male gametophyte bears antheridium which produces flagellated sperms/antherizoids
Cont’d • The female gametophyte bears archegonium which produces eggs • The sperm cell swims in a film of water into the archegonium to fertilize the egg which develops into a zygote • The zygote develops into embryo • The embryo develops into sporophyte which contain the sporogenous cells that undergo meiosis to produce the spores.
Life Cycle of Marchantia polymorpha
Classification eg. Marchantia polymorpha • Kingdom: Plantae • Division: Bryophyta • Class: Hepaticopsida/Marchantiopsida • Subclass: Marchantiae • Order: Marchantiales • Family: Marchantiaceae • Genus: Marchantia • species: Polymorpha
Class: Anthocerotopsida (hornworts) • Habitat: live in disturbed habitats eg fallow fields and roadsides • X’tics: Presence of a single large chloroplast in each cell resembles certain algal cells than plant cells. In contrast, mosses, liverworts and other plants have many disk-shaped chloroplast per cell. • -In the common hornwort, Anthoceros natans, the archegonia and antheridia are embedded in the thallus/ gametophyte rather than on archegoniophores and antheridiophores
Cont’d • -After fertilization and development, a needle- like sporophyte emerged out of the gametophyte thallus, forming a spike or ”horn” and hence the name hornwort • -A single gametophyte often produces multiple sporophytes • -Meiosis occurs to produce spores in each sporangium. • -Sporangium split open from the top to release spores
Cont’d • Each spore germinate to give rise to a new gametophyte • In hornworts the sporophyte continue to grow from their bases attached to gametophyte (indeterminate) unlike mosses and liverworts (determinate). The life cycle is the same as that of Hepaticopsida Assignment: Write short notes on life cycle of the Anthocerotopsida
Anthoceros sp
Class Bryopsida Classification of Funaria hygrometrica • Kingdom: Plantae • Division: Bryophyta • Class: Bryopsida • Subclass: Funariidae • Order: Funariales • Family: Funariaceae • Genus: Funeria • Species: hygrometrica
Class: Bryopsida/Musci (Mosses) • Gametophytes • The gametophyte generation is dominant. • Gametophytes of mosses have green "leafy shoots" and multicellular rhizoids (structures that resemble roots). • The rhizoids- anchorage, absorption of water and mineral nutrients. • They possess stomata and cuticle (adaptations to live on land). • They lack vascular tissues, hence no true roots, stems, or leaves. • Gametophytes may grow either erect or flat on the ground. • Their size is restricted by lack of vascular tissue. Some species of moss have water-conducting cells and sugar-conducting cells but lack lignin
Cont’d • The gametophyte often bears gametangia at the top of the plant. Many mosses have separate sexes; male plant that bears the antheridia and a female plant that bears the archegonia. Other mosses produce antheridia and archegonium on the same plant. • The archegonia produce eggs, and antheridia produce antherizoids/motile sperm. • The sterile layer that comprises the outer part of archegonia and antheridia helps protect the delicate gametes by preventing them from drying out. • The unprotected motile sperm must swim in a film of water or splash by rain droplets from the antheridium to the archegonium which secrets chemicals to attract and guide the sperm to fuse with the egg to form a diploid zygote
Cont’d – Sporophyte • The zygote formed in the archegonium after fertilization grows by mitosis into a multicellular embryo. • A sporophyte develops from an embryo which is still enclosed in the archegonium of the female gametophyte plant. • The sporophyte is permanently attached to the gametophyte and nutritionally depend on it. • The mature sporophyte consists of a foot which anchores the sporophyte to the gametophyte and absorbs minerals and nutrient from it, a seta/stalk, and a capsule which contains sporocytes/sporogenous cells/spore mother cells
Cont’d • The sporogenous cells/sporocytes within the sporophyte undergo meiosis to produce a single kind of haploid spore(homosporous). If a spore lands in a suitable place, it germinates into a protonema, the initial filamentous stage of a gametophyte plant. • The protonema form buds each of which grows into a green gametophyte and the life cycle continues.
Life cycle of mosses
Importance of mosses – Food for mammals, birds – Important in soil formation and reduction of soil erosion, particularly along stream banks – Commercial moss- peat moss (Sphagnum) multiplied in moss bioreactors are developed as a new tool to monitor air pollution. • Fuel (dried). • Soil conditioner- helps retain moisture. • Also used by florists to hold moisture. • They also store large amount of carbon which helps to reduce global warming or greenhouse effect
Characteristics of Pteridophytes • Members of this group are most primitive living vascular plant. No Seed formation. • Pteridophytes are mostly terrestrial sometimes growing in the moist, cool and shady places eg Selaginella sp, Lycopodium sp, Equisetum sp, Nephrolepis sp, Dryopteris sp etc. Some are aquatic like Azolla sp and Salvinia sp. • Pteridophytes shows large variation in form, size and habit. It ranges from the small annuals to the large tree like perennial forms.
Characteristics of Peridophytes cont’d • The plant body is differentiated into root, stem and leaves. • The prominent plant body is the sporophyte and represents the dominant phase in the life cycle. The sporophyte is nutritionally independent of the gametophyte. • Plants are either homosporous (eg.) Equisetum, Lycopodium, Pterium, Nephrolepis or heterosporous (eg. Selaginella, Marsilea, Salvinia).
Characteristics of Peridophytes cont’d • The leaves vary from the simplest form to the compound nature. On the basis of the nature of leaves the pteridophytes are classified into: i. Microphyllous pteridophytes, ii. Macrophyllous pteridophytes. • The stem is usually branched; branching is monopodial or dichotomous. • The leaves and stem possess filliform trichomes. Stomata are present on both the upper and lower surface of the leaf.
Characteristics of Pteridophytes cont’d. • The young leaves are coiled in nature- crosier or fiddlehead. • It possesses underground horizontally growing stems called rhizomes. • The stele is a protostele (Lycopodium, Selaginella) Siphonostele (Equisetum, Ophioglossum pendulum) dictyostele (Pteris, Nephrolepis) or polycyclic (Angiopteris).
Characteristics of Peridophytes cont’d • The root and stem possess a well-developed vascular system having the xylem and phloem. The cambial ring is absent so the secondary growth does not occurs. • The leaves bearing sporangia are known as sporophylls. • In the heterosporous plants, the sporophylls with megasporangia are called megasporophyll and with microsporangia are called microsporophyll. • Asexual reproduction is by spores produced in the sporangia, fragmentation and budding also occur
Characteristics of Peridophytes cont’d • The sporangia are borne on the ventral surface of the leaves. In one member, Ophioglossum a fertile spike is present. • The embryo of pteridophytes is classified into exoscopic embryo and endoscopic embryo. • Life cycle of pteridophytes is diplobiontic. It exhibits heteromorphic alternation between the gametophytic and sporophytic generation. That is morphologically distinct sporophytic and gametophytic generation.
Characteristics of Pteridophytes Cont’d • In heterosporous species; the microspores give rise to the male gametophyte and megaspore give rise to the female gametophyte. • In the homosporous pteridophytes antheridia and the archegonia are borne on same prothallus. • Water is essential for fertilization. • Presence of protective jacket cells in the sex organs.
Four classes of Kingdom Pteridophyta: • 1. Psilotopsida (Psilotum); • 2. Lycopsida (Selaginella, Lycopodium; the club mosses), • 3. Equisitopsida/Sphenopsida (Equisetum, horse tails) and • 4. Filicopsida/Pteropsida (The Ferns eg Nephrolepis, Dryopteris, Pteris, Adiantum= Terrestrial Marselia, Azolla, Salvinia = Aquatics).
Kingdom: Plantae Division: Pteridophyta Class: Psilotopsida Order: Psilotales Family: Psilotaceae Genus: Species: Psilotum nudum Classification of Psilotum nudum
Class: Psilotopsida eg. Psilotum (whisk fern) • Family Psilotaceae, order Psilotales, and class Psilotopsida . The name of the genus is from Greek psilos = naked, because it lacks organs, such as leaves and roots normally found in other ferns. • Psilotum- dichotomous branching, terminal sporangia and a lack of roots but are anchored by creeping rhizomes. • Has vascular tissue
Cont’d • Psilotum nadum has vertical stem that exhibits dichotomous branching and horizontal underground rhizome. Upright stem of Psilotum are green and carry out photosynthesis. • The gametophyte is non-photosynthetic due to its subterranean location. It is nourished symbiotically by mycorrhizal fungi • Antherozoids are spirally coiled and multi- flagellated.
Class: Lycopsida • The sporophyte plant body is differentiated into definite root, stem and leaves. • The sporophytes are dichotomously branched. • The leaves are usually small thus microphyllous. • The xylem in stem exarch. • Sporangia are borne singly on the adaxial (upper) surface of the sporophylls. • The spores may be of either one type i.e., homosporous (e.g., Lycopodium) or two types i.e., heterosporous (e.g., Selaginella). • The spores develop into independent gametophyte.
Class Lycopsida: :Order Lycopodiales : Life cycle of Lycopodium
Order: Selagineliales Eg. Selaginella sp.
Class: Equisitopsida/Sphenopsida • Stems and branches are jointed with nodes and internodes. The internodes have longitudinal ridges and furrows. • The leaves are extremely reduced and borne in whorls at the nodes of aerial branches and stems. • Branches arise in whorls. • The sporangia develop on appendage called sporangiophore. Sporangial walls are thick. • Most of the members are homosporous including Equisetum. However, some extinct forms were heterosporous (e.g., Catamites casheana). • The gametophytes are exosporic (free-living, develop outside spore walls) and green. • 7. Antherozoids are multiflagellated. • 8. The embryo is without suspensor and is exoscopic
Class: Filicopsida/Pteropsida • The sporophytes are usually perennial in nature and differentiated into roots, stem and spirally arranged leaves. • 2. Most of the members grow in moist and shaded habitats, either epiphytic or terrestrial. A few are aquatics. • 3. Mostly, the rhizomes are short and stout. • 4. The leaves are large (megasporophylls), pinnately compound and described as frond, except Ophioglossum (simple leaf). • 5. The rachis is covered with brown hairs (ramenta).
Con’d. • 6. Young fronds show circinate vernation (coiling of leaves), except Ophioglossum. • 7. The stele in Pteropsida shows a wide variety of types, e.g., protostele, siphonostele, • solenostele, dictyostele and polycyclic stele. • 8. Most ferns are homosporous, but a few aquatic members are heterosporous. • 9. Sporangia are borne at the tips or at the margin of the pinnule or to the abaxial surface of the fronds. Phyllosporous- sporangia are born on the leaf. Stachyosporous- sporangia are born in the axil of the leaf.
Classification Ferns Kingdom: Plantae Subkingdom: Tracheobionta Division: Pteridophyta Class: Filicopsida The are 4 orders: Order: Hydropteridales Order : Marattiales Order : Ophioglossales Order : Polypodiales
Cont’d Order: Hydropteridales Family: Azollaceae – Azolla family, Genus: Azolla Family Marsileaceae – Water-clover family Genus: Maesilea Species: ancyclopoda Family: Salviniaceae – Floating Fern family Genus: Salvinia Species: natan
Classification of Angiopteris evecta Kingdom Plantae Subkingdom Tracheobionta Division Pteridophyta Class Filicopsida Order Marattiales Family Marattiaceae Genus Angiopteris Species evecta
Classification of Botrychium virginianum Kingdom Plantae Subkingdom Tracheobionta Division Pteridophyta Class Filicopsida Order Ophioglossales Family Ophioglossaceae Genus Botrychium Species: virginianum
Classification of Nephrolepis biserrata Kingdom Plantae Subkingdom Tracheobionta Division Pteridophyta Class Filicopsida Order Polypodiales Family Dryopteridaceae Genus Nephrolepis Species: biserrata
Class: Filicopsida Order: Filicales Eg Fern (Nephrolepis sp. Or Dryopteris sp)
Life Cycle of a Fern