Lab 8 - Primitive tree -Bryophytes,Ferns and Fern Allies
As we pass from mosses to ferns, we check out a gradual shift fromprimitiveto modern traits. There space two significant trends friend should focus on intoday"slab. The an initial is a change in life cycles, the 2nd is a changeinbasic interior structure.
You are watching: Which of the following structures represents the sporophyte stage of the bryophytes?
First, all tree undergo one alternation of generations,between a haploid gametophyte stage and a diploid sporophytestage. In the many primitive plants, prefer mosses, the gametophyte isdominant(i.e. It"s huge and green). In greater plants favor ferns and also fern allies,the sporophyte phase is dominant. Gametophytes develop gametes (spermandeggs) in a one-of-a-kind structure called a gametangium (-ia), whilesporophytesproduce spores in a unique structure dubbed a sporangium(-ia).
Second, all plants need to gain water to their cells.Primitivebryophyteslike mosses and liverworts space so little that they deserve to rely top top diffusionto move water in and also out that the plant. Mosses have a few strands ofwaterconducting organization in their main stem, but nothing prefer the huge andwell arranged network of pipe in tracheophytes, or "tubeplants".The vascular organization in the more advanced ferns and also "fernallies"are made up of xylem and phloem, which command water,nutrients,and food throughout the tree body. We"ll watch at this tissues in alaterlab.
Bryophytes likewise need a moist setting to reproduce. Theirflagellatedsperm should swim through water to reach the egg. For this reason mosses andliverwortsare minimal to moist habitats. There are no mosses in the desert.Butmosses are surprisingly resistant to dry up, and also can survive underveryharsh conditions. Mosses are the most abundant plants in both theArcticand the Antarctic. Asexual reproduction in bryophytes is accomplishedbyfragmentation or by tiny vegetative "sprouts" referred to as gemmae,whichform in special little structures referred to as gemmae cups.
Mosses and also liverworts are lumped with each other as bryophytes,plantslacking true vascular tissues, and also sharing a variety of other primitivetraits. They likewise lack true stems, roots, or leaves, though they havecellsthat do these basic functions. The leafy green plant that we seewhen us look in ~ a moss or a liverwort is yes, really the gametophyte,which is the leading stage in all bryophytes. The sporophytesofbryophytes carry out not have actually a free-living existence. Lock grow directly outof the fertilized egg in the archegonia, and remain dependency on theparentgametophyte for their nutrition.Characteristics of Divisions
Division Bryophyta - (9,500 sp.) - mosses, Mnium, Sphagnum
Mosses come in two an easy types, a cushiony type, v erect stalks,and a feather type, which creates flattened carpet of low-lying and highlybranched moss plants. In both cases, the leafy eco-friendly gametophytes aredioeciousThey deserve to be masculine plants, with antheridia in ~ the optimal of the plant, orfemaleplants, through archegonia at the top. Remember that these gametophytesarealways haploid (1N) plants.
Sperm are developed within each antheridium, and also an egg ineacharchegonium.Because the plant is currently haploid, these gametes deserve to be created bymitosis,simple cabinet division. The sperm swims to the archegonia with a thinfilm of water, drawn by a chemistry attractant produced by the femaleplant,then swims down the neck that the archegonia come the egg. A good morningdewis more than enough water for the sperm come swim. As soon as the spermentersthe archegonia, the fuses through the egg. The 2N zygote creates into adiploidsporophyte plant, a small stalk that grows directly out that the optimal ofthearchegonium. This stalk is at first green, and also photosynthetic, butlaterturns brown and becomes basically a parasite ~ above the femalegametophyte.
The sporophyte plant consists of a stalk, and also a tiny capsuleon the top. Within the capsule, cells undergo meiosis to producetetradsof haploid spores. As soon as the capsule is ripe, the hinged lid oroperculumopens up, and the spores space quickly dispersed by wind and water. Thesporesgerminate into a tiny eco-friendly thread, i m sorry looks like a simple strand ofgreen algae. This similarity is one an ext clue the bryophytes aredescendedfrom green algae. This at an early stage threadlike stage is dubbed the protonema(= first thread, many = protonemata, like stigma/stigmata). The newadultgametophytes grow from a small bud that creates on the protonema.Eventuallythese gametophytes will grow to develop gametes, and also the totality cyclewillstart end again. Mosses can also reproduce asexually by fragmentationor by growing little vegetative buds referred to as gemma, which can break offand grow into a new plant .
While bryophytes in basic are an ext interesting than important, inthe normal sense, a conspicuous exemption are mosses the the genus Sphagnum.Sphagnummoss forms thick mats which end up being compressed right into peat, which deserve to beusedas fuel, although it’s an extremely smoky. Peat also contains various other plants suchas reeds, that flourish amid the sphagnum. In dried form, peat moss isremarkablyabsorbent and, and has been provided for diapers, for enriching bad gardensoils, and also as a ar dressing for wounds. Whereas noodle absorbs 4-6timesits dry weight, dried sphagnum can absorb 20 times its own weight influids!Peat bogs are very important and also interesting ecosystems. Sphagnummosses considerably increase regional acidity by release H+ ions, and also the pHof peat bogs deserve to drop come 4 or lower, perhaps the most acidic naturalenvironment.Peat bogs cover around 1% that the Earth’s land surface, an area abouthalfthe dimension of the joined States.
Division Hepaticophyta - (9,000 sp.), liverworts, Marchantia,Conocephalum, Porella
Liverworts have the easiest bodies of all the green plants. Thegametophyte,the leading stage, looks prefer a flat scaly leaf, with prominent lobes.It look at for every the people like a small flattened liver, hence thescientificname hepatico-phyta = liver plant. During the middle Ages, thissimilaritycaused physicians to prescribe liverwort for illness of the liver.Accordingto the doctrine of Signatures the Creator had actually designed all of nature,includingplants, v our welfare in mind. People believed that plants had actually beenintentionally designed to resemble the guts of the body they weresupposedto heal! hence liver-wort, wyrt gift the Anglo-Saxon word for herb.Theshape of the liverwort to be the signature the the Creator in nature. Canyou guess what walnuts were supposed to cure ? (diseases that thebrain)
Liverworts re-publishing the basic properties the bryophytes, yet are notveryclosely regarded mosses or hornworts. Plenty of botanists think lock mayhaveevolved independently, indigenous a different group of green algae. Because that onething,liverworts don’t save food as starch yet as oils. If you gain theaquaticliverwort Porella in lab, take a sniff of the jar, but not toodeep!It smells the rancid oils, oils the went a tiny funky while the plantwas gift shipped. An additional characteristic unique to liverworts is theirlack that stomata, i m sorry are found in all other plants, including mossesand hornworts.
In many varieties of liverworts, such as Marchantia, the oneyouwill most likely see in lab, the antheridia and also archegonia are not ontopof the plant, however hanging under from the underside of odd littlestructuresthat look prefer tiny umbrellas. (These umbrella-shaped structures arecalledthe antheridiophore and also archegoniophore). The bi-flagellated spermswimsto the egg, and also fertilization takes location to form a diploid (2N)zygote.The tiny diploid sporophytes, which remain attrached come the parentplant,have a very an easy structure. Meiosis in ~ the sporophyte produces anumber of haploid spores. This spores room surrounded by curious longandtwisted moist cells dubbed elaters. When the capsule dries and also bursts,the elaters twist and jerk about in a method that scatters the spores inall directions. Liverworts can additionally reproduce asexually by way ofspecialstructures dubbed gemmae cups. These tiny cups have the right to be easilyseenon the surface ar of the plant. Every gemma cup consists of a variety of tinyplantletscalled gemmae, and also a single drop the water will disperse them. Theselittlevegetative “clones” will then thrive into a brand-new gametophyte.
Division Anthocerophyta - (100 sp.), hornworts, Anthoceros
The environment-friendly gametophytes that the hornwort look an extremely much choose aliverwort.But their tiny sporophytes an ext closely resemble those the mosses. Thesporophytes prosper out the the gametophyte, and look favor a tiny uprighthorn. Like mosses, hornworts have stomata, and also so are most likely morecloselyrelated come mosses and also other plants than to the liverworts lock matresemble.These plants are symbiotic through the cyanobacteria Nostoc. Thecyanobacteriafixes nitrogen for the hornwort.Taxonomy
Division Bryophyta - mosses (Mnium, Sphagnum; fr.Gr.bryon= moss)
Division Hepaticophyta - liverworts (Marchantia,Conocephalum,Porella; fr.Gr. Hepato = liver)
Division Anthocerophyta - hornworts (= Anthocerotophyta; Anthoceros;fr.Granthos = flower, keras = horn)Terms alternation that generations gametophyte gametangium (-ia) archegonium (-ia) antheridium (-ia) sporophyte sporangium (-ia) spore capsule protonema vascular system gemmae gemmae cupTo Do and also View
Examine the living mosses on display. Notice the little capsuleson height of the tiny sporophytes. Mosses generally flourish in one of twogrowthtypes: cushiony moss and feathery moss.
Examine slides the the antheridia and archegonia. The sausageshaped antheridia produce sperm, and the flask shame archegoniaproduces eggs.
Examine slides of the moss capsule, and identify the spores.
Examine slides that the protonema. What kind of algaedoesit remind you of? This resemblance is additional evidence the greenalgaegave rise to all greater plants.
Examine the terrestrial liverworts Marchantia and also Conencephalum(oneor both need to be top top display). Exactly how does their growth habit different fromthat that the mosses? can you see any kind of gemmae cups ~ above the uppersurfaceof this plants?
Examine slides that the liverwort Marchantia.
Examine the aquatic liverworts prefer PorellaandRiccia(one or both need to be top top display). Notice how they differ from themoreterrestrial creates of liverwort.
Look at the maintained liverworts, and also observe your distinctreproductive structures (they watch like little green umbrellas). Howdoestheir life cycle differ from mosses?
Examine slides of the hornwort Anthocerophyta.Things come Remember
Know the life bike of the moss in detail, and also be may be torecognizethe assorted stages.
Hint: Be certain you recognize the basic life bicycle ofplants,and deserve to tell which stages are haploid gametophytes (1N) or diploidsporophytes(2N). We"ll find out several life cycles in lecture and in laboratory (moss,fern,pine, flower plant), but every one of them room variations on the samebasictheme.Ecological, Evolutionary, and Economic Importance
Mosses are crucial in landscaping and also gardening, particularly peatmoss(Sphagnum).
Peat moss (Sphagnum) has been provided historically as dressingsfor wounds.
Peat moss have the right to be supplied as fuel.
Mosses room the most primitive life land plants.
Hornworts contain symbiotic nests of the cyanobacteria Nostoc.
shining club moss
Introduction to Tracheophytes - Ferns and Fern Allies
Tracheophytes (vascular plants) completed the conquest of theearth’s surface begun by the more primitive bryophytes. Just as theevolutionof spores to be the key to the invasion of the land surface ar bybryophytes,the development of complicated vascular organization let tracheophytes completetheconquest of dry land. Over there are around 250,000 species of vascularplants,grouped in ripe divisions. Tracheophytes all have a fine developedroot-shootsystem, v highly committed roots, stems, and leaves, andspecializedvasculartissue (xylem and also phloem) that function like miniature pipe toconductfood, water, and nutrients transparent the plant. Since ferns and also fernallies posses true vascular tissues, castle can flourish to be much largerandthicker than the bryophytes.
The ferns and also fern allies (non-seed tracheophytes) note two majorevolutionarystrides. In these and also in all more advanced plants, the leafy environment-friendly diploidsporophyte currently becomes the leading stage. The small gametophytemay be one of two people autotropophic (like the fern prothallus) orheterotrophic(like the gametophytes of some lycopsids), and also is generally complimentary livingand elevation of the parental sporophyte. Uneven the vascularsporophytes,the gametophytes have no vascular tissue at all. This gametophytes aretherefore an extremely small, and develop best in moist areas, whereby they canabsorbwater straight from your surroundings.
Like the bryophytes, ferns and fern allies are still minimal tomoisthabitats. Your flagellated sperm require a slim film the water come swimbetweenthe antheridium and also the archegonium. And also when the infant sporophyte growsup native the gametophyte, it is exposed to desiccation (drying up). Thisbasic strategy that a free-swimming sperm and also a non-motile egg is sharedby plants, animals, and also algae. It provides sense, because it method onlyoneset that gametes has to make the perilous journey external of theorganism.
ground pine tree (Lycopodium) showing strobili
The ferns and also fern allies germinate indigenous spores. These plants aremostlyhomosporous- their spores are identical and you can"t distinguish which willgrow right into male or woman plants. Castle are additionally monoecious -boththe archegonia and also antheridia (male and female reproductive structures)are borne top top the exact same plant. Comparison these primitive vascular plantswiththe more advanced seed plants, the gymnosperms and angiosperms, whichgerminatefrom seeds fairly than native spores. Particle plants room all heterosporous.It is simple to differentiate the bigger female megaspore fromthesmaller male microspore. The sperm of seed plants have actually noflagella.They lack antheridia, and also only a few still have actually an archegonia. Unlikethemore primitive ferns and also fern allies, seed tree are mostly dioecious,having different male and female plants.
In plenty of of these primitive plants, specific leaves are specializedforreproduction. These modified leaves, or sporophylls, bear thesporangiaat their bases. This sporophylls typically branch out from a shortenedstem,forming a club shaped structure referred to as a strobilus. The pineconeand the flower are elaborate variations on these primitive strobili.
There room four divisions of non-seed tracheophytes, vascular plantsthat reproduce by way of spores, the Psilophyta, Lycophyta,Sphenophyta,and Pterophyta. Prior to these non-seed tracheophytes evolved, thebryophyteswere the dominant form of tree life. The evolution edge of having amore reliable conducting system, and also a well-developed root-shootsystemenabled them to outcompete bryophytes. If you’re lucky sufficient to seegroundpine or various other club mosses growing in the the shade of a huge pine tree,thinkfor a moment around how these small plants were once the master of theplanet,forming large forests v trunks indigenous 20 come 100 feet tall!Taxonomy
Tracheophytes (vascular tissue, no seeds)
Division Lycophyta - society moss, quillworts (Lycopodium,Selaginella)
Division Sphenophyta - horsetails (Equisetum; fr.L.equus= horse)
Division Psilophyta - whisk fern (Psilotum)
Division Pterophyta - true ferns (Pteris; fr.Gr.pteridion= tiny wing)Terms homosporous heterosporous megaspores microspores rhizomes sporophylls strobilus (-i) sori indusium (-ia) prothallus fiddleheadsCharacteristics the Divisions
Division Psilophyta - (fr Gr. Psilo = smooth), whiskferns,Psilotum
There are only two life genera the whisk ferns, sole survivors the alarge and widespread group of early on land plants. In enhancement to thelivingDivision Psilophyta, the psilopsids, there are two extinct departments ofprimeval vascular plants. The primitive whisk ferns resemble theseextinctpioneers in numerous ways. They space the only living vascular plants thatlacka root-shoot system, a characteristic lock share v both extinctDivisionsof ancestral vascular plants. Some recent molecular evidence suggeststhatone, or also both, that the life genera that psilopsids may actually bemoreclosely related to ferns, prefer a fern that has reverted come moreprimitivetraits. If this is true, then Psilophyta will join the ranking of thenumerousextinct departments of plants.
Psilopsids are uncovered in tropical and subtropical areas, and occursthroughoutthe southern US. I once discovered one cultivation on my ago porch under theleavesof a spider plant. Whisk ferns space a common weed in greenhouses alloverthe world. Lock are an easy green upright stems, through dichotomousbranching.They have no leaves, and also no true roots. The external tissues that the stemdoall the photosynthesizing. A portion of the stem called a rhizome runsalong the ground, or just listed below it. A rhizome is a horizontalstemthat spreads the plant around. Roots prosper out the bottom the therhizome,and a new plant deserve to arise at the same suggest from the top.
The environment-friendly stem-like tree is the diploid sporophyte, the dominantstagein the life cycle. In the tiny sporangia (bright yellow) that formalongthe upper stems, the spore mom cell creates haploid spores by meiosis.Their gametophytes room tiny small thread-like underground tree thatlack chlorophyll, and live as heterotrophs in the soil, feather andactingmuch favor a small fungi. The actually consists of a symbiotic fungi, thesamemycorrhizae the live in the rhizomes of the adult sporophyte.
Division Lycophyta - (1,000 sp., fr. Gr. Lycos=wolf), clubmosses,quillworts, Lycopodium (podus=foot)
Their space only 5 living genera the lycopsids, but at one time fromthe distant Devonian, about 400 mya, well right into the Carboniferous, theywere the dominant type of vegetation top top the challenge of the Earth. Now theyare diminished to a shadow of their glorious past, inconspicuous littleplantsin the forest understory. The tropical species are tiny epiphytes(plantsthat flourish on various other plants).
Their roots thrive from special underground stems dubbed rhizomes, asdo most of these primitive tracheophytes. In some species thesporophyllsare combined in v the scale-like leaves. In countless species, thesporophyllsare organized into strobili, therefore the typical name that “club moss”. Thesperm swim under the strobilus to the archegonia, and also the zygote thatformsis preserved in the cone, which ripens and falls come the ground. Thegametophytesare independent and free-living, They are curious creatures the lookandact nothing choose their sporophyte parents. They can be eitherheterotrophicor autotrophic, and usually have actually a symbiotic fungi linked withthem.Many the the lycopsids space heterosporous. Selaginella is a goodexampleof a heterosporous plant.
Division Sphenophyta - (15 sp., one genus, fr. Gr.sphen=wedge),horsetails, Equisitum
In garbage places, disturbed areas like trails and railroad beds, andin weird corners the fields and forests you could find another little plantquietly dreaming of its former splendor, the horsetail. Horsetailsappearedin the so late Devonian, and were among the dominant forest trees forhundredsof millions of years. Only one genus of Sphenophyta still exists, thegenusEquisetum,and it may be the earliest living genus of plants on earth. Horsetailstoweredamong the Carboniferous forests, reaching heights that 30-60 feet. Muchofthe coal deposits we manipulate for fuel today were formed from horsetailsand various other trees throughout the Carboniferous, toward the finish of thePaleozoic.
Horsetails have actually true roots, stems, and also leaves, though the pipeline arelittle much more than planarization stems. Their hollow, ribbed tribe arejointed,kind of favor a stalk the bamboo, and also a whorl of pipeline arises in ~ eachjoint.The plants space spread vegetatively through rhizomes. The stems feeling veryrough,because the epidermal tissues are impregnated v tiny seed ofsilica(sand). This probably helps safeguard the plant against herbivores. Theserough stems made this plant appropriate for pioneer ladies to usage forscrubbingpots and also pans, thus its other usual name, “scouring rush”.
The environment-friendly plant we see is the diploid sporophyte generation. Thestalkscan be very branched vegetative stalks, which actually look likehorsetails, or directly unbranched reproductive stalks, which room tippedwitha large strobilus containing the sporangia. The homosporous sporesdevelopinto a teeny-tiny eco-friendly gametophyte, just a few mm long, that lookslikethe gametophyte the a fern. The gametophyte is haploid, free-living, andautotrophic.
Division Pterophyta - (12,000 sp., fr. Gr. Pteridion=littlewing),ferns
Ferns probably developed from the psilopsids, sometime in theDevonian,relatively at an early stage in land tree evolution. Lock are really abundant anddiverse, varying in size from a solitary centimeter to tree 24 meterstallwith 5 meter fronds. Ferns have been far better competitors v seedplantsthan various other seedless vascular plants, and also are a conspicuous component of thelandscape transparent the world, yet especially in the tropics, where75%of their 12,000 species occur.
Ferns are reasonably advanced plants, with true roots, stems andleaves.The blade of the fern is called a frond, and the small individualleafletsare called pinnae. Ferns have true leaves, what botanists callmacrophylls.While the leaves of more primitive plants, which space calledmicrophylls,are simply expansions of the epidermis the the stem, the leaves of fernsand greater plants were formed as a internet of tissue extended betweensmallterminal branches. The pipeline of higher plants, and the modifiedleaves that comprise the jaw cone and the flower.
The life bike of the fern is typical of other non-seed vascularplants.The leafy green plant is the sporophyte. Abundant fronds developsclustersof little sporangia ~ above the underside the the frond. This clusters ofsporangiaare called sori (sing. Sorus). Sori room often protected by atinyumbrella-like cap dubbed an indusium (-ia). Ferns room mostlyhomosporous,though some space heterosporous. The heterosporous state is a moreadvancedcondition, that seems to have developed independently in several groupsofplants.
The haploid spores are developed by meiosis within the sporangium. They ejected in a miniature explosion brought about by the unequal dry ofthealternate thick and thin-walled cells that line the outer surface. Thetop pulls slowly back until it reaches a an essential point and then snapsforward in ~ an remarkable speed. In ~ that dimension scale, the expulsion offernspores is just one of the most explosive events in nature. The sporesgerminateinto tiny gametophytes. The tiny heart shaped gametophyte is dubbed aprothallus,literally “first-body” (pl prothalli). The prothallus has actually no vasculartissue.Its small size allows it rely entirely on diffusion. Its tiny rhizoidsareassociated v mycorrhizal fungi. The tiny prothallus is green, andphotosynthetic, and also bears one of two people antheridia and also archegonia, orsometimesboth together, on its upper surface (lab slides have both ~ above sameprothallus).The archegonia are always found at the arch of the heart, and also theantheridiaare tucked away amongst the small rhizoids at the various other end. The spermswimsto the egg come fuse right into a diploid zygote. The brand-new sporophyte growsdirectlyout that the top of the gametophyte. Once it an initial begins come uncurl, thefrond looks choose the scrolled neck the a violin or fiddle, and also thisstageof breakthrough is called a fiddlehead.
To Do and also View
Examine the life lycopsids top top display. Why room they calledclub mosses? notification that quillworts and also Selaginella space verydifferentin appearance from the club mosses.
Examine slides that Selaginella"s strobilus. Determine megasporesand microspores.
Examine the living horsetails top top display. An alert theprominentstrobiliofthe reproductive stalks, and also the bushy growth form of the vegetativestalks(if available).
Examine the life whisk ferns ~ above display. Psilopsidshave a an easy dichotomous branching pattern. You might see tiny yellowsporangiaon the branches. Whisk ferns lack strobili. These primitive plants areclosely concerned ferns.
Examine the life ferns on display. Can you see any fiddleheads?Look because that the rhizomes. Rhizomes are modified horizontal stemsbearingroots, that run along or simply underneath the ground, and also spread fernsandfern allies around.
Examine the life fern prothallus on display under adissectingmicroscope. Note its characteristic heart shape. Part prothalli mayhavea tiny new fern emerging from the notch of the "arch" heart, where thearchegoniaarelocated.
Examine slides that the prothallus: discover the archegonia(can you watch an egg?).
Examine the fern leaflet on screen under the dissectingmicroscope.Notice the significant indusia, and the small sporangiapeekingout from beneath. You"ll view a couple of groups of sporangia that have losttheirindusium. If you"re lucky, as the warm of the microscope dries the end theleaflet, you might see the sporangia eject the spores. Yet don"tblink- it"s among the fastest and also most explosive plot in nature. Usage highpowerto observe the spores.
Examine slides that the sori and indusia; usage high powerto observe the spores.Things to Remember
Know the life bicycle of the fern. Recognize specimens andslidesof the various stages.Economic, Ecological, and Evolutionary Importance
Ferns and also fern allies are mainly responsible for our moderndepositsof coal.
The fiddleheads the some varieties of ferns space edible.
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Ferns are necessary for the florist, gardening and also landscapeindustries.Consider This
Why room all this plants limited to wet habitats?
Which group of protists provided rise to these plants? (How execute we know?)
Why is the epidermis that the horsetail therefore rough? What does the needprotectionfrom?
All of the fern allies in this lab as soon as towered 50-100 feet or more.What happened?
Links come Explore
Bryophyte taxonomy, images, and more at:
Get info around bryophytes from the Missouri factory Garden at:
Lie down amongst the ferns in ~ the American Fern Society, try theirlengthylist that links:
Basic info on ferns and fern allies, complete with images, courtesyof Texas A&M:
Look for ferns top top the "tree that life" at