Plant Diversity 1 Lecture PDF

Plant Diversity 1 Concepts 29.1-29.3; Campbell. Biology. 3rd ed. Outline • 1. Origin, traits and diversification of plants • 2. Nonvascular plants (bryophytes) • 3. Seedless vascular plants (ferns and other relatives) 1. Origin, traits and diversificatio n of plants • Plants evolved from Charo...

Plant Diversity 1 Concepts 29.1-29.3; Campbell. Biology. 3rd ed. Outline • 1. Origin, traits and diversification of plants • 2. Nonvascular plants (bryophytes) • 3. Seedless vascular plants (ferns and other relatives) 1. Origin, traits and diversificatio n of plants • Plants evolved from Charophyte green algae (recall Ch 28 on Protists) • Both share the following: • Rings of cellulose synthesizing proteins embedded in plasma membrane synthesize cellulose (Charophyte green algae and plants only) • Structure of flagellated sperm the same in charophyte and some species of plants • Formation of a phragmoplast which is cell structure involved in cell plate formation and subsequent division of daughter cells is found in certain Charophytes and plants ONLY Additional Evidence • Sporopollenin • A tough polymer surrounding the spores of certain charophytes and is chemically similar to that which surrounds the spores of plants • Prevents zygote from drying out • Likely what allowed the first plants to successfully live a terrestrial existence Derived Traits of Plants • Traits that are specialized and unique to plants that did not exist in previous ancestors • Such traits include • Cuticle (prevent drying out) • Stomata (gas exchange and minimize water loss) • Alternation of Generations (not found in Charophyta but in other algae) • Multicellular, Dependent Embryos • Walled Spores produced in Sporangia (bryophytes and seedless vascular plants) • Multicellular Gametangia (structures that produce gametes ie. sperm and egg) • Apical Meristems (growing point at the tips of roots and shoots) • Cuticle = Plant surfaces developed fatty/waxy cuticle to retard water loss. • Stomata = specialized pores on leaves that support photosynthesis by allowing gas exchange of CO2 taken in the outside air and release of O2 ( O2 is a bi-product of photosynthesis) • Stomata also regulate water evaporation and minimize water loss by closing under hot, dry conditions https://www.nature.com/a rticles/s41477-019-0390-3 • Alternation of Generations • two distinct phases of life cycle • includes a sporophyte stage (multicellular diploid 2n and produces spores by meiosis) and the gametophyte stage (multicellular haploid n which produces gametes by mitosis) Hornwort sporophyte growing from gametophyte • Multicellular, Dependent Embryos • Zygotes (diploid cell resulting from fusion of gametes) develop into embryos • Plant embryos are protected and retained in maternal tissues • Harsh external environments; prevent drying out; placenta and placental transfer cells for nutrient transfer • Walled Spores Produced in Sporangia • Sporophyte (diploid 2n phase of life cycle) has organs called sporangia (sporangium singular) that produce spores (haploid n) through meiosis. • Spores are produced through asexual reproduction • Outer tissues of the sporangia protect the developing spores until they are ready to be released into the air • Spore walls have sporopollenin which further protect them from damage and harsh environmental conditions • Multicellular Gametangia • Gametophyte (haploid n phase of life cycle) produced gametangia which are gamete (sperm and egg) producing structures) • Female gametangia are called archegonia • Male gametangia are called antheridia • Many present-day plants have flagellated sperm that are released from the antheridia and swim in rain splash or droplets of water to the archegonia where fertilization occurs, and the zygote develops into an embryo Gametophyte produces gametes in gametangia Sporophyte produces spores in sporangia. • Apical Meristems • Meristems - Permanent regions of growth and active cell division • Cells produced at meristems are similar to stem cells in animals and capable of differentiating into multiple cell and tissue types • Apical Meristems - Found at the tips of roots and shoots • Roots and shoots increase in length as the apical meristems produce new cells (= primary growth). • Shoot apical meristems also generate leaves in most plants Distinguishing Plant Groups • Nonvascular plants • Bryophytes (mosses, liverworts and hornworts) • Vascular seedless plants • Lycophytes (club mosses, spikemosses, quillworts) • Monilophytes (ferns, horsetails, whisk ferns) • Vascular seed plants • Gymnosperms (conifers, ginkgos, cycads, gnetophytes) "naked seeds" because seeds are not enclosed in chambers or fruits • Angiosperms (flowering plants) with seeds contained in fruits Other Distinguishing Characters • Presence or absence of vascular tissue • Xylem = water and mineral conducting tissue • Phloem = sugar (carbohydrate) conducting tissue • Bryophytes (liverworts, mosses and hornworts) lack vascular tissues. Other phyla (lycophytes, monilophytes, gymnosperms, angiosperms) HAVE vascular tissues • True root systems • ABSENT in Bryophytes and Seedless Vascular Plants (ferns and their relatives) • Water required for fertilization • Required in Bryophytes, Lycophytes and Monilophytes. NOT required in other phyla • Flowers and Fruits • ONLY in Angiosperms (flowering plants) • Production of pollen • NO pollen in Bryophytes, Lycophytes and Monilophytes. Pollen production in Gymnosperms and Angiosperms only • Production of seeds • Bryophytes (liverworts, mosses and hornworts) and Lycophytes (club mosses, spikemosses, quillworts) and Monilophytes (ferns, horsetails, whisk ferns) DO NOT produce seeds. • Seed production is unique to Gymnosperms and Angiosperms http://jessicalovespla nts.blogspot.com/20 12/06/comparison-b etween-mosses-ferns .html 2. Non-Vascular Plants (Bryophytes) Bryophytes Phylums: Hepaticophyta – Liverworts Anthocerophyta – Hornworts Bryophyta – Mosses Bryophyte Characteristics – The Gametophyte • Gametophyte (n) is the dominant phase of the life cycle, meaning they are usually larger and longer living than the sporophytes • Gametophyte are comprised of a protonema (mass of green, branched, one cell thick filaments) • Bryophyte gametophytes can form multiple gametangia (gamete producing structures) • Archegonia = female gametangia = produce a single egg and where zygote develops following fertilization • Antheridia = male gametangia = produce many sperm • Most bryophytes are homosporous or bisexual (one gametophyte has both archegonia and antheridia) • Sperm are flagellated and water is required for fertilization • sperm (n) swim through droplets of water and rain splash to the female archegonia where they fuse with the egg (n) and form a zygote (2n) • Bryophytes typically found in moist environments • Lack true roots • absorb water and minerals over their leafy gametophyte surfaces • Rhizoid – used to anchor the gametophyte to a substrate (rock, tree log etc) • Bryophytes often have mycorrhizal fungi associated with their rhizoids • Lack vascular tissue • water conduction is minimal and usually only between nearby cells • Bryophytes are ground hugging and low growing because lack the vascular tissue which allows for long distant transport of water and minerals within the plant body Bryophyte Characteristics – The Sporophyte • Usually green and photosynthetic when young but cannot live independantly of the gametophyte • Remain attached to the gametophyte and absorb sugars, amino acids and water through the "foot" of the sporophyte • Parts of the sporophyte • Foot = the part of the sporophyte that is embedded into the gametophyte archegonia and absorbs nutrients from the gametophyte • Seta = the "stalk" of the sporophyte which conducts nutrients and water to the sporangium • Capsule = the sporangium = structure that produces spores by meiosis Figure 29.8 The life cycle of a moss Bryophytes – Leaves and Stems MOSS LIVERWORT HORNWORT http://bioteaching.files.wordpress.com/2011/06/img5.jpg Bryophytes – Waterproof cuticle MOSS LIVERWORT HORNWORT http://bioteaching.files.wordpress.com/2011/06/img5.jpg Bryophytes - Stomata MOSS LIVERWORT HORNWORT Economic and Ecological Importance of Bryophytes • Peat mosses are ecologically important in bogs (Wet muddy ground). HUGE carbon sinks. Becoming controversial to use it for fuel or agriculture/horticulture purposes • Conditioner for dry soil (peat retains moisture) • Contribute minimal to zero fungi, pest, and weeds ie. sterile http://www.kissner.com/peat-moss/ http://www.kissner.com/peat- 3. Ferns and other seedless vascular plants Seedless vascular plants Phylums: Lycophyta – spike mosses, quillworts, club mosses Monilophyta – ferns, horsetails, whisk ferns Characteristics – The Sporophyte • Sporophyte (2n) is the dominant stage of the life cycle ,meaning they are usually larger and longer living than the gametophytes. In ferns, the familiar leafy plants are the sporophyte • Sporophyte produces spores (n) in sporangia (spore producing structures, singular sporangium) that are found on modified leaves called sporophylls • In ferns (Monilophytes), sporangia found on the underside of the sporophylls • In many Lycophytes, groups of sporophylls form into a cone-like structure called strobili whisk fern A fern • Most seedless vascular plants are homosporous meaning they produce one type of spore which gives rise to a gametophyte that produces both sperm and egg (ie. bisexual) . • Some seedless vascular plants are heterosporous, meaning they produce two types of spores Figure 29.13 The life cycle of a fern • Sperm are flagellated and water is required for fertilization • Similar to Bryophytes • sperm (n) swim through droplets of water and rain splash to the female archegonia where they fuse with the egg (n) and form a zygote (2n) • Lycophytes and Monilophytes are typically found in moist environments • Simple roots • Non branching, simple, but have root hairs for water and mineral uptake • Vascular tissue • Two types of vascular tissue, xylem and phloem • 1. Xylem = conducts water and minerals • Xylem contains tracheids (lignified cells) which provide structure and support permitting vascular plants to grow tall and conducts water and minerals to the far-reaching parts of the plant • 2. Phloem = transports sugars, amino acids and other organic products Characteristics – The Gametophyte • Gametophyte (n) is shorter-lived and independent phase of the life cycle. Often found at soil surface or below surface. Some are very tiny and hard to detect. • Similar to Bryophytes, the gametophyte of seedless vascular plants have gamete producing structures • Archegonia = female gametangia = egg producing structure and where zygote develops following fertilization • Antheridia = male gametangia = sperm producing structure • Lacks true roots • absorb water and minerals over their leafy gametophyte surfaces • Rhizoid – used to anchor the gametophyte to a substrate (rock, tree log etc) Figure 29.13 The life cycle of a fern Human and ecological relevance of ferns • House plants • Function well as air filters • Plants filter out carbon dioxide, carbon monoxide, hydrogen, methane, alcohol, ammonia, formaldehyde and benzene. http://www.africanbabiesdontcry.com/2012/03/how-to-have-cleaner-purer-air-in-you r.html Human and ecological relevance of ferns • Folk medicine • Traditional Chinese Medicine – drugs to promote urination (diuretics), relieve swelling Gu-Sui-Bu Drynaria roosii Working with Ferns (2010), pp 285-304 (Publisher: Springer) Human and ecological relevance of ferns • Vegetable fern (Diplazium esculentum) / cooked rhizomes (stem) as food http://www.shutterstock.c om/pic-68801038/stock-p hoto-vegetable-fern-dipla zium-esculentum-is-an-e dible-fern-found-through out-asia-and-oceania-theyoung.html Thank you The End Questions? 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