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