Ch. 22 Bryophytes - The Non-Vascular Plants PDF

Chapter 22 Survey of Plant Taxa: Bryophytes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Learning Objectives ❖ List the features that distinguish the Plant Kingdom from other Kingdoms. ❖ Explain how bryophytes as a group differe from other plants...

Chapter 22 Survey of Plant Taxa: Bryophytes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Learning Objectives ❖ List the features that distinguish the Plant Kingdom from other Kingdoms. ❖ Explain how bryophytes as a group differe from other plants. ❖ Explain how a liverwort thallus can be distinguished from that of a hornwort. ❖ Explain which features liverworts, hornworts and mosses have in common and state how their sporophyte differ. ❖ Describe the structures involved in the life cycle of a moss an in which structures mei9osis and fertilization occur. General Terminology ❖ Sporophyte (2n): spore producing phase of life cycle ❖ Gametophyte (n): gamete producing phase of life cycle ❖ Gametangia: any cell that produces gametes ❖ Archegoniophore: stalk bearing archegonium ❖ Archegonium: multicellular female gametangium, bears eggs (gametes) ❖ Antheridiophore: stalk bearing antheridium ❖ Antheridium: multicellular male gametangia, bears sperm General Terminology ❖ Sporocyte (2n): cell that becomes 4 haploid spores/nuclei from meiosis ❖ Sporangiophore: stalk bearing sporagium ❖ Sporangium: structure where spores are produced ❖ Spore: reproductive cell(s) that can develop into gameteophyte or other structures • Vegetative spores formed through mitosis • Meiospores formed through meiosis ❖ Sporophyll: a modified leaf that bears sporangia ❖ Paraphyses: sterile spore-bearing layer, support General Terminology ❖ Monoecious: one house • ❖ Both male and female reproductive structures are produced by one individual plants Dioecious: two houses • Male reproductive structures produced by the male plant • Female reproductive structures produced by the female plant Note: These terms can refer to either the gametophyte or sporophyte Ex./: dioecious sporophyte or dioecious gametophyte Introduction ❖ Numerous adaptive strategies = ~300,000 plant sp ❖ Dominate all terrestrial communities ❖ Most plants are photosynthetic Cones on a Fir Tree Pitcher Plant Rafflesia arnoldii Orchid Indian Pipe (non PS) Introduction ❖ Plants and green algae share the following: • Chlorophylls a and b, carotenoids • Starch as food reserve • Cellulose in cell walls • Phragmoplast and cell plate during cell division ❖ Shared features suggest common ancestor. ❖ Land plants first appeared 400 million years ago. ❖ Ancestor progressed from aquatic to land habitat even earlier. Evolutionary History of Plants ❖ For ~500 my, algae were confined to watery domain ❖ Limited b/c water provided: • Place for Reproduction • Provide Structural Support • Prevent Water Loss • Provide some protection from UV radiation Evolutionary History of Plants ❖ Adaptations needed to leave water & come to land • Ways to obtain nutrients and water • Ways to keep water and stop desiccation (death by dehydration) • Ways to get enough but not too much sunlight • Ways to get CO2 and release O2 • Ways to structurally support the body • Ways to protect and spread offspring Evolutionary History of Plants ❖ Adaptations needed to leave water & come to land ❖ Ways to obtain nutrients and water • ❖ Ways to keep water and stop desiccation (death by dehydration) • ❖ Stay close to water or develop vascular tissues (“plumbing”) Waxy cuticle on all surfaces keeps water inside Ways to get CO2 and release O2 gases – Adaptive structures for gas exchange o stomata, lenticels, etc. Evolutionary History of Plants ❖ Adaptations needed to leave water & come to land ❖ Ways to get enough but not too much sunlight • ❖ Develop habitat appropriate interception structures (leaves) and ways to mitigate “sunburns” Ways to structurally support the body • Develop cell and body architecture that is strong enough to grow up for competition of resources and withstand winds Evolutionary History of Plants ❖ Adaptations needed to leave water & come to land ❖ Ways to protect and spread offspring • Develop embryo protection strategies (fruit, nuts, seeds) – The structures provide protection & minimal nutrients until germination • Gametangia (gamete-producing structures) and sporangia (spore-producing structures) became multicellular and surrounded by jacket of sterile cells. • Zygotes developed into multicellular embryos within parental tissues that originally surrounded egg. Evolutionary History of Plants ❖ Adaptations needed to leave water & come to land ❖ Ways to protect and spread offspring • Develop strategies for embryo dispersal – – – Wind = grasses, pines, maples, dandelions Water = coconut palms, mangroves, water lilies Animal = beggars ticks, pecan, mistletoe Alternation of Generations Life Cycle ❖ The Diploid Generation alternates with the Haploid Generation ❖ Diploid (Sporophyte, 2N): • Multicellular individual: produces spores (N) by meiosis in the sporangium structure • Spore (N) will become the gametophyte (N) ❖ Haploid (Gametophyte, N): • Multicellular individual (N) that produces gametes (N) • Gametes (N) fuse in fertilization to form zygote (2N) • Zygote (2N) will become the sporophyte (2N) 14 Generalized Alternation of Generation Life Cycle Reduction in the Size of the Gametophyte 17 Evolutionary History of Plants ❖ Categorized in two ways: • Non-vascular (bryophytes) or Vascular (tracheophytes) • Seedless (pteridophytes) or Seeded (gymnosperms and angiosperms) Non-Vascular Plants (Bryophytes) • 3 phyla – Liverworts (Hepatophyta) – Hornworts (Anthocerophyta) – Mosses (Bryophyta) Vascular Plants (Tracheophytes) • 9 phyla – 4 seedless phyla – 5 seeded phyla 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 Questions????? A. B. L. D. K. E. C. M. F. J. G. N. H. I.