Bryophytes PDF

Introduction to the Bryophytes (Non-vascular plants) ❖ About 23,000 species of bryophytes ❖ Include mosses, liverworts, and hornworts Occupy wide range of habitats: Damp banks, trees, logs Bare rocks in scorching sun Frozen alpine slopes In elevations from sea level up to 5,500 meters or more Bryoph...

Introduction to the Bryophytes (Non-vascular plants) ❖ About 23,000 species of bryophytes ❖ Include mosses, liverworts, and hornworts Occupy wide range of habitats: Damp banks, trees, logs Bare rocks in scorching sun Frozen alpine slopes In elevations from sea level up to 5,500 meters or more Bryophytes (Nonvascular (NV) Plants ) ❖ More primitive characteristics & 1st to colonize land ❖ Evolved ~ 445 – 490 mya (Ordovician period) ❖ Gametophyte Dominant ❖ Typically low lying (no structural support) ❖ Need to stay close to water (living & offspring dispersal) ❖ Do not have roots, stems or leaves b/c ? ❖ ❖ may have arisen independently from ancestral green algae. often have mycorrhizal fungi associated with their rhizoids. Bryophytes (Nonvascular (NV) Plants ) ❖ None have true xylem or phloem. Many have hydroids for water conduction. – ❖ Most water absorbed directly through surface. A few have leptoids for food-conduction. To reproduce sexually, must have external water Bryophytes (Nonvascular (NV) Plants ) ❖ ❖ Gametophyte (N) generation Dominant Exhibit alteration of generations In mosses, leafy plant is major part of gametophyte generation. – Gametophyte produces gametes. Sporophyte generation grows from gametophyte. – Sporophyte produces spores. Bryophytes (Nonvascular (NV) Plants ) ❖ Great Ecological Impacts Break down rock to soil Hold moisture and minerals in soil Ex./ Peat Moss (Sphagnum) absorbs water – Often added to garden soils to increase water holding capacity – Undecayed peat is used as fuel & building materials – Scotch Whiskey is traditionally filtered with peat moss – Holds great amounts of CO2 Bryophytes (Nonvascular (NV) Plants ): Phylum Hepatophyta: Liverworts ~8-9,000 species Most primitive of the nonvascular Commonly found in humid, shady environs 2 types – Thallose liverworts o – Common type specimen Leafy liverworts o most numerous species number Nonvascular Plants: Bryophytes: Phylum Hepatophyta: Liverworts ❖ ❖ Thallose liverworts Flattened, lobed thalli (singular: thallus). Constitute about 20% of species Best known species in genus Marchantia sp.. Thallus forks grows dichotomously – Each branch has an apical notch and central groove. o Meristematic cells in notch continue to divide. Nonvascular Plants: Bryophytes: Phylum Hepatophyta: Liverworts ❖ Both thallose and leafy gametophytes develops from spores. When spores germinate they may produce protonema. – ❖ Protonema - Immature gametophyte consisting of short filaments In thalloid liverworts growth is prostrate and one-celled rhizoids on the lower surface anchor plant. Nonvascular Plants: Bryophytes: Phylum Hepatophyta: Liverworts ❖ Marchantia sp. Upper surface = diamond-shaped segments – – Each segment has small bordered pore opening into chamber. Short, erect rows of cells with chloroplasts sit on floor of chambers. Nonvascular Plants: Bryophytes: Phylum Hepatophyta: Liverworts ❖ Thalloid liverworts Marchantia sp.- Asexual reproduction: – Via: – Fgmentation – Gemmae cups with gemmae (singular: gemma) o Gemmae - Tiny, lens-shaped pieces of tissue that become detached from thallus o Produced in gemmae cups scattered over upper surface of thallus Nonvascular Plants: Bryophytes: Liverworts: (Marchantiophyta): Marchantia sp.: Asexual Reproduction Nonvascular Plants: Bryophytes: Liverworts: (Marchantiophyta): Marchantia sp.: Sexual Reproduction ❖ Gametangia formed on gametophores. Male gametophore = antheridiophore – Antheridia that contain sperm – Sperms have numerous flagella. Nonvascular Plants: Bryophytes: Liverworts: (Marchantiophyta): Marchantia sp.: Sexual Reproduction ❖ Gametangia formed on gametophores. Female gametophore = archegoniophore – Archegonia with eggs in rows and hang down beneath spokes of archegoniophore. egg Marchantia sp. after fertilization Before fertilization (n) Archegonium (n) w/ egg (n) Archegoniophore (N) (l.s.) (2n) Nonvascular Plants: Bryophytes: Liverworts: (Marchantiophyta): Marchantia sp.: Sexual Reproduction: Sporophyte (2n) ❖ Sporophyte dependent on gametophyte for sustenance. Foot of sporophyte anchors to archegoniophore. Seta - Short stalk Capsule (sporangium) - Meiosis produces haploid spores inside. Other cells inside capsule do not undergo meiosis and develop into elaters with spiral thickenings. Nonvascular Plants: Bryophytes: Liverworts: (Marchantiophyta): Marchantia sp.: Sexual Reproduction Immature sporophyte protected by calyptra caplike tissue that grows out from gametophyte. Elaters sensitive to humidity Twist and untwist rapidly to aid break up spore mass Aids in spore dispersal Capsule(sporangium) splits at maturity to release spores. Marchantia sp. Life cycle Mt (n) (n) Mt (n) Mt Mt Mt Mt (n) (n) (n) Mt (n) (n) released (n) (n) (n) (n) Mt Retained (2n) archegonium (n) (2n) (2n) Retained archegonium (n) Sporocytes (2n) (spore mother cells) (2n) (sporangium) (2n) Retained Mt Elaters (2n) Mt (2n) Retained Nonvascular Plants: Bryophytes: Phylum Hepatophyta: Leafy Liverworts: ❖Superficially resemble mosses ❖Most numerous group ~85% of species ❖Tropical forest and fog belts ❖ Two rows of partially overlapping leaves No midrib Often have folds or lobes Cells contain oil bodies. Phylum Hepatophyta: Leafy Liverworts: Third row of underleaves often present. Archegonia and antheridia produced in cuplike structures composed of modified leaves, in axils of leaves or on separate branches. Sporophyte pushes out from among leaves. spherical gemmae on apical "leaves" Nonvascular Plants: Bryophytes: Hornworts Phylum Anthocerophyta – Thin rosette or ribbon like thallus – 1-5 cm tall – Photosynthetic, but also have symbiosis with cyanobacteria (can fix nitrogen from air) – Found moist soil, often mixed with grass – Rarely found on bare rock or trees Phylum Anthocerophyta – Hornworts ❖ Structure and form: Mature sporophytes look like miniature greenish-blackish rods. Gametophytes thalloid – Cells with only one large chloroplast – Thalli have pores and cavities filled with mucilage that often contain nitrogen-fixing bacteria. Only about 100 species worldwide Asexual reproduction by fragmentation of thallus. Phylum Anthocerophyta – Hornworts: Sexual Reproduction Archegonia and antheridia produced in rows just beneath upper surfaces of gametophytes. ❖ Sporophyte: – With numerous stomata – Meristem above foot continually increases length of sporophyte from base. – Meiosis occurs in sporophyte to produce spores. – Diploid elaters, that function similar to those of liverworts, intermingled with spores. Nonvascular Plants (Bryophytes): Phylum Bryophyta: Mosses ❖ Largest phyla of bryophytes ❖ ~15,000 species ❖ Mostly inhabit damp, shady environs Some can live in deserts May look complete dead when in drought, but with rain they recover brilliant green coloration ▪ Mycorrhizae associations being investigated, but largely absent in Bryophyta Phylum Bryophyta: Mosses Peat Moss (Sphagnum sp) NV Plants: Phylum Bryophyta – Mosses ❖ Have phyllids: leafy like blades nearly always one-cell thick, except at midrib (costa) never lobed or divided. Cells contain numerous lens shaped chloroplasts. Axis stem-like, with Often with central strand of hydroids NV Plants: Phylum Bryophyta – Mosses ❖ Structure, form and classes: Sphagnum/Peat moss leaves have: – large transparent cells w/o chloroplasts that absorb water – small, green, photosynthetic cells sandwiched between. NV Plants: Phylum Bryophyta – Mosses ❖ Sphagnum/Peat moss leaves : Phylum Bryophyta – Mosses: Sexual Reproduction ❖ Gametangia at apices of leafy shoots. Archegonium cylindrical with egg in swollen base, and neck above containing narrow canal. Paraphyses - multicellular filaments scattered among archegonia. – Phylum Bryophyta – Mosses: Sexual Reproduction ❖ Antheridia on short stalks, surrounded by walls one cell thick. Sperm cells, paired flagella, formed inside. Sperm forced out antheridium top. Paraphyses scattered among antheridia. Phylum Bryophyta – Moss Life Cycle Phylum Bryophyta – Mosses: Sexual Reproduction ❖ Archegonia release substances that attract sperm. ❖ Sperm swim down neck of archegonium. ❖ Zygote grows into spindle-shaped embryo. ❖ Top of archegonium splits off and forms cap on top of sporophyte = calyptra. ❖ Mature sporophyte consists of capsule, seta and foot. ❖ Meiosis produces spores inside capsule. ❖ ❖ Peristome, composed of one or two rows of teeth, under operculum at tip of capsule. Peristome opens or closes in response to humidity. Spores develop into filamentous protonema that produces buds that develop into leafy gametophytes. Phylum Bryophyta – Mosses: Sexual Reproduction Moss Sporangium Introduction to the Bryophytes ❖ Luminous mosses are found in caves and in other dark, damp places. aka Schistostega pennata, or goblin's gold Human and Ecological Relevance of Bryophytes ❖ Pioneer species on bare rock after volcanic eruptions or other geological upheavals = succession Accumulate mineral and organic matter that is utilized by other organisms ❖ Retain moisture, and reduce flooding and erosion ❖ Indicators of surface water ❖ Packing material ❖ Peat mosses most important bryophyte to humans. Soil conditioner due to high absorptive capacity Poultice material due to antiseptic properties and absorbency Fuel