Practical 6 : Seed Plants (Gymnosperms and Anginosperms) Objectives: At the end of this lab, stdents shold be able to: i! ii! ii! iii! iii! iv! iv!
"esc "escri ribe be the the fea feat trres of of see seed d plan plantt lif life e cyc cycle le and and the the con conce cept pt of of the the dominant generation! "esc "escri ribe be the the lif life e hist histor orie ies s and and rel relat ated ed repr reprod odc cti tive ve str strc ct tre res s of gymnosperms and anginosperms! Smma Smmari ri#e #e the the featr featres es that that dist distin ing gis ish h gymno gymnospe sperm rms s and angi angino nospe sperm rms! s! "isc "iscss ss the the adva advant ntag ages es of of seed seed pla plant nts s to domi domina nate te lan land d and and thei theirr evoltionary adaptations on land!
$%periment &: Gymnosperms 'ntrodction Gymnosperms (* species in 6+ genera) are ancient seed planmts that inclde gingos ("ivision Gingophyta), cycads ("ivision -ycadophyta), conifers ("ivision from the Gree .ood roots gymnos, meaning /naed0, and sperma, meaning /seed0! 1hey are naed2seeded plants meaning that the ovle, .hich becomes a seed, is e%posed on the sporophyte at pollination! 3atre seed are not enclosed in a frit as are those of 4o.ering plants! Gymnosperms are best no.n for their characteristic cones, called strobili! 1hese strobili display sprorangia and their sbse5ently developing, ovles and pollens! Gymnosperms do not re5ire .ater for sperm to s.im to reach the egg as do seedless plants! 'nstead, immense amont of .indblo.n pollen are prodced! 3ost gymnosperm cones, inclding the familiar pine cone, are comple% .horls of lea4ie, .oody arond a central a%is! 1he smallest cones inclde those of the jnipers ( Juniperus Juniperus) .hich have 4esh scales fsed into a strctre resembling a berry! berry! 1he larger cones may .eight +g and are prodced by cycads! 'n most gymnosperm species, the female megostrobils is larger and distinctive from the male microstrobils!
3aterials 7iving or preserved specimens of • • •
Gingo (Ginkgo biloba ) -ycad (Cycas sp.) Pine (Pinus sp.)
Prepared slide of gymnosperms -ompond microscope "issecting microscope Slide and coverslip "istilled .ater
Procedre A gingo: &! $%amine a oreoared slide of male strobils of Ginkgo biloba. 'dentify the microsporophyll, microsprorangim and strobils a%is! ! $%amine a prepared slide of female strobils of Gunkgobiloba. 'dentify the megasprophyll, megasprorangim, and strobils a%is! A cycad: &! $%amine a female cycad! 'dentify leaves, megasprorophylls, megasporangim and developing seeds! ! 1he pollen cone bears on male cycad! $%amine pollinate cone and identify microsporophyll, microsporangim, and pollen grains!
A pine: &! Obtain a male cone and female cone of Pinus sp. -an yo di8erentiate bet.een the t.o cones9 ! $%amine a prepared slide of longitdinal section of female cone! 7oo for megasporophyll, megasporangia, and ovle! ! $%amine a prepared slide of longitdinal section of male cone! 7oo for megasporophyll, megasporangia, and pollen grains! ! ;ertili#ation occrs after the pollen tbe penetrates the megasporangim and allo.s sperm to enter the archegonim and fses .ith the egg! 1he #ygote .ill form after fertili#ation! $%amine a prepared slide of the developing embryo of Pinus sp. +! Obtain matre seed cone! ;ind the seed .ith .ing attached to the ovliferos scale!
"iscssion
1he gymnosperms are a grop of seed2prodcing plants that incldes conifers, cycads, Gingo, and Gnetales! 1he term =gymnosperm= comes from the Gree composite .ord >?@BCDEF@H (>?@BH gymnos, =naed= and CDIF@J sperma, =seed=), meaning =naed seeds=, after the nenclosed condition of their seeds (called ovles in their nfertili#ed state)! 1heir naed condition stands in contrast to the seeds and ovles of 4o.ering plants (angiosperms), .hich are enclosed .ithin an ovary! Gymnosperm seeds develop either on the srface of scales or leaves, often modiKed to form cones, or at the end of short stals as in Gingo!1he gymnosperms and angiosperms together compose the spermatophytes or seed plants! Ly far the largest grop of living gymnosperms are the conifers (pines, cypresses, and relatives), follo.ed by cycads, gnetophytes (Gnetm, $phedra and
Wamiaceae! -ycads have changed little since the Tr assic, compared to some major evoltionary changes in other plant divisions! -ycads are gymnosperms (naed seeded), meaning their nfertili#ed seeds are open to the air to be directly fertili#ed by pollination, as contrasted .ith angiosperms, .hich have enclosed seeds .ith more comple% fertili#ation arrangements! -ycads have very speciali#ed pollinators, sally a speciKc species of beetle! 1hey have been reported to K% nitrogen in association .ith a cyanobacterim living in the roots! 1hese ble2green algae prodce a neroto%in called L3AA that is fond in the seeds of cycads! 1his neroto%in may enter a hman food chain as the cycad seeds may be eaten directly as a sorce of 4or by hmans or by .ild or feral animals sch as bats, and hmans may eat these animals! 't is hypothesi#ed that this is a sorce of some nerological diseases in hmans! 7astly, Pines are conifer trees in the gens Pins piXnXs, in the family Pinaceae! 1hey are the only gens in the sbfamily Pinoideae! 1he Plant 7ist compiled by the Yoyal Lotanic Gardens, Ze. and 3issori Lotanical Garden accepts &6 species names of pines as crrent, together .ith + nresolved species and many more synonyms!
$%periment : Angiosperms 'ntrodction Angiosperms are the most abndant, diverse, and .idespread of all plants! 1hey are sccessfl becase they are strctrally diverse, have e[cient vasclar system, share a variety of mtalisms (especially .ith insects and fngi), and have short generation times! ;lo.ering plants are important to hman becase or .orld economy is over.helmingly based on them! 'ndeed, .e eat and se vegetative strctres (roots, stems and leaves) as .ell as reprodctive strctre (4o.er, seed, and frits)! \o .ill Knd that many of the vegetative strctres are 5ite similar to those of more, ancient plants sho.n! 1he roots, stems, and leaves of 4o.ering plants fnction jst as those of ferms and cone bearing plants! ;lo.ers and frits, ho.ever are ni5e adaptations of angiosperms! Liologists believe that the e%traordinary adaptiveness of these strctres has led to the proliferation of the incredible diversity fond among 4o.ering plants! 3aterials 7iving specimens of angiosperms (dicots ] monocots) .ith roots, steams, leaves, 4o.ers, frits and seed! ( Imperata cylindrical, zea mays, Carica papaya, Phaseolus sp.) Prepared slides of angiosperms (dicots ] monocots) -ompond microscope "issecting microscope Slide and coverslip ;orceps "istilled .ater
Procedre
Yoot: &! Obtains a root of a dicots and mococots for morphology and anatomy stdy! ! 7oo for the root systems of representative dicot and moncot! -an yo give the fnction of these roots9 ! -ross section of dicot root sho.s the central stele is srronded by a thic corte% and epidermis! 'dentify the follo.ing: epidermis, corte%, parenchyma cells, starch grains, pericycle, endodermis, phloem, and %ylem! ! -ross section of monocot root sho. this root has a vasclar cylinder of %ylem and phloem that srronds a central pith! 'dentify the follo.ing: epidermis, corte%, endodermis, -asparian strip, pith, phloem, and %ylem! +! Obtain a prepared slide of the roots for some other species and distingish their strctre!
Steams: &! Stdy the longitdinal section of shoot tip of representative dicot and monocot (fresh prepared slide or prepared slide)! 'dentify the follo.ing: leaf, leaf primordim, apical meristem, grond meristem, a%illary bd, vasclar bndle, and pith! ! Obtain a dicot and monocot and mae a cross section of the stems and e%amine the arrangement of vasclar bndles! -ompare the anatomy bet.een this dicot and monocot! ! ;or both type of plants, identify epidermis, corte%, phloem, %ylem, cambim, pith and vasclar bndle! 7eaves: &! 7oo for fresh specimen provided in lab! ;lo.ering plants sho. a variety of morphology to identify, sch as, leaf arangements and leaf venation! ! sing fresh prepared slide or prepared slide of some 4o.ering plants, stdy the strctre of the leaves! Notice that the lesves have common featres: cticle, air space, lo.er epidermis, pper epid ermis, palisade mesophyll, spongy mesophyll, and vasclar bndle! ;lo.ers: &! 7oo for longitdinal section of some 4o.ers! Name the par ts of a 4o.er: stigma, pistil , style, sepal, receptacle, pedncle, petal, Klament, stamen, and anther!
! $%amine a prepared slide of a cross section of matre anther (lily anther)! ;ind sections of for microsporangia! 7oo for pollen grains .ithin a microsporangim! ! $%amine a prepared slide of a cross section of an ovary (lily ovary)! ;ind the several ovles! 7oo for megaspores mother cell .ithin megasporangim! Stdy the megasporangim develops! 'dentify the placenta, integments, microphyle, egg cell, central cell, and polar nclei! ! Observe the demonstration slide of doble fertili#ation and identify the #ygote, primary endosperm ncles, and central cell of the female gametophyte! ;rits and seeds: &! Get a sample opf dry, dehiscent frits (peants)! 'dentify the frit .all, cotyledon, plmle of embryo, radicle, cotyledon, and seed coat! ! Get a sample of simple 4esy frits (tomato, a berry)! 'dentify pericarp, mesocarp, endocarp, locle, seed and placenta! ! $%amine a prepared slide of corn grain ( Zea mays), a caryopsis frit! 1he pericarp of a corn grains is tightlt nited and inseparable from the seed! 'dentify the pericarp, endosperm, cotyledon, coleptile, plmle, plmle bd , embryo, radicle, and coleorhi#a!
"iscssion 1he 4o.ering plants (angiosperms), also no.n as Angiospermae bor 3agnoliophyta, are the most diverse grop of land plants, .ith abot +*,*** species! 7ie gymnosperms, angiosperms are seed2prodcing plantsM they are distingished from gymnosperms by characteristics inclding 4o.ers, endosperm .ithin the seeds, and the prodction of frits that contain the seeds! $tymologically, angiosperm means a plant that prodces seeds .ithin an enclosre, in other .ords, a friting plant! 1he term =angiosperm= comes from the Gree composite .ord (angeion2, =case= or =casing=, and sperma, =seed=) meaning =enclosed seeds=, after the enclosed condition of the seeds! 1he ancestors of 4o.ering plants diverged from gymnosperms in the 1riassic Period, dring the range + to * million years ago (mya), and the Krst 4o.ering plants are no.n from &6* mya! 1hey diversiKed e%tensively dring the 7o.er -retaceos, became .idespread by &* mya, and replaced conifers as the dominant trees dring &** to 6* mya! A stem is one of t.o main strctral a%es of a vasclar plant, the other being the root! 1he stem is normally divided into nodes and internodes! 1he nodes hold one or more leaves, as .ell as bds .hich can gro. into branches (.ith leaves, conifer cones, or in4orescences (4o.ers))! Adventitios roots may also be p rodced from the nodes!1he internodes distance one node from another! 1he term =shoots= is often confsed .ith =stems=M =shoots= generally refers to ne. fresh plant gro.th inclding both stems and other strctres lie leaves or 4o.ers! 'n most plants stems are located above the soil srface bt some plants have ndergrond stems!Stems have for main fnctions .hich are: a! Spport for and the elevation of leaves, 4o.ers and frits! 1he stems eep the leaves in the light and provide a place for the plant to eep its 4o.ers and frits! b! 1ransport of 4ids bet.een the roots and the shoots in the %ylem and phloem c! Storage of ntrients d! Prodction of ne. living tisse! 1he normal life span of plant cells is one to three years! Stems have cells called meristems that annally generate ne. living tisse!
A leaf is an organ of a vasclar plant and is the principal lateral appendage of the stem! 1he leaves and stem together form the shoot! ;oliage is a mass non that refers to leaves collectively! 1ypically a leaf is a thin, dorsiventrally 4attened organ, borne above grond and speciali#ed for photosynthesis! 3ost leaves have
distinctive pper (ada%ial) and lo.er (aba%ial) srfaces that di8er in color, hairiness, the nmber of stomata (pores that intae and otpt gases) and other featres! 'n most plant species, leaves are b road and 4at! Sch species are referred to as broad2leaved plants! 3any gymn osperm species have thin needle2lie leaves that can be advantageos in cold climates fre5ented by sno. and frost! 7eaves can also have other shapes and forms sch as the scales in certain species of conifers! Some leaves are not above grond (sch as blb scales)! Scclent plants often have thic jicy leaves, bt some leaves are .ithot major photosynthetic fnction and may be dead at matrity, as in some cataphylls, and spines)! ;rthermore, several inds of leaf2lie strctres fond in vasclar plants are not totally homologos .ith them! $%amples inclde 4attened plant stems (called phylloclades and cladodes), and phyllodes (4attened leaf stems), both of .hich di8er from leaves in their strctre and origin! 3any strctres of non2vasclar plants, and even of some lichens, .hich are not plants at all (in the sense of being members of the ingdom Plantae), loo and fnction mch lie leaves! 1he primary site of photosynthesis in most leaves (palisade mesophyll) almost al.ays occrs on the pper side of the blade or lamina of the leaf bt in some species, inclding the matre foliage of $calypts palisade occrs on b oth sides and the leaves are said to be isobilateral! A 4o.er, sometimes no.n as a bloom or blossom, is the reprodctive strctre fond in 4o.ering plants (plants of the division 3agnoliophyta, also called angiosperms)! 1he biological fnction of a 4o.er is to e8ect reprodction, sally by providing a mechanism for the nion of sperm .ith eggs! ;lo.ers may facilitate otcrossing (fsion of sperm and eggs from di8erent individals in a poplation) or allo. selKng (fsion of sperm and egg from the same 4o.er)! Some 4o.ers prodce diaspores .ithot fertili#ation (parthenocarpy)! ;lo.ers contain sporangia and are the site .here gametophytes develop! ;lo.ers give rise to frit and seeds! 3any 4o.ers have evolved to be attractive to animals, so as to case them to be vectors for the transfer of pollen! 'n addition to facilitating the reprodction of 4o.ering plants, 4o.ers have long been admired and sed by hmans to beatify their environment, and also as objects of romance, rital, religion, medicine and as a sorce of food! 'n botany, a frit is the seed2bearing strctre in angiosperms formed from the ovary after 4o.ering! ;rits are the means by .hich angiosperms disseminate seeds! $dible frits, in particlar, have propagated .ith the movements of hmans and animals in a symbiotic relationship as a means for seed dispersal and ntritionM in fact, hmans and many animals have become dependent on frits as a sorce of food! Accordingly, frits accont for a sbstantial fraction of the .orld^s agricltral otpt, and some (sch as the apple and the pomegranate) have ac5ired e%tensive cltral and symbolic meanings! 'n common langage sage, =frit= normally means the 4eshy seed2associated strctres of a plant that are s.eet or sor, and edible in the ra. state, sch as apples, bananas, grapes, lemons,
oranges, and stra.berries! On the other hand, in botanical sage, =frit= incldes many strctres that are not commonly called =frits=, sch as bean pods, corn ernels, tomatoes, and .heat grains! 1he section of a fngs that prodces spores is also called a friting body! A seed is an embryonic plant enclosed in a protective oter covering no.n as the seed coat! 't is a characteristic of spermatophytes (gymnosperm and angiosperm plants) and the prodct of the ripened ovle .hich occrs after fertili#ation and some gro.th .ithin the mother plant! 1he formation of the seed completes the process of reprodction in seed plants (started .ith the development of 4o.ers and pollination), .ith the embryo developed from the #ygote and the seed coat from the integments of the ovle! Seeds have been an important development in the reprodction and sp read of gymnosperm and angiosperm plants, relative to more primitive plants sch as ferns, mosses and liver.orts, .hich do not have seeds and se other means to propagate themselves! 1his can be seen by the sccess of seed plants (both gymnosperms and angiosperms) in dominating biological niches on land, from forests to g rasslands both in hot and cold climates! 1he term =seed= also has a general meaning that antedates the above_anything that can be so.n, e!g! =seed= potatoes, =seeds= of corn or sn4o.er =seeds=! 'n the case of sn4o.er and corn =seeds=, .hat is so.n is the seed enclosed in a shell or hs, .hereas the potato is a tber!3any strctres commonly referred to as =seeds= are actally dry frits! Plants prodcing berries are called baccate! Sn4o.er seeds are sometimes sold commercially .hile still enclosed .ithin the hard .all of the frit, .hich mst be split open to reach the seed! "i8erent grops of plants have other modiKcations, the so2called stone frits (sch as the peach) have a hardened frit layer (the endocarp) fsed to and srronding the actal seed! Nts are the one2seeded, hard2shelled frit of some plants .ith an indehiscent seed, sch as an acorn or ha#elnt!
Post2lab `estions &! o. to distingish bet.een a amel and female cone of pine9 A female pine cone, also called a megasporangiate strobils, consists of cone or seed scales that hold t.o ovles, the nfertili#ed seeds! 't taes abot t.o years for female pine cones to become matre!
their homes becase of its beaty and resistance to insects! 1he Lible records that the -edar of 7ebanon .as sed for temples or other e%travagant strctres! Some conifers e%crete a resin to protect themselves from insects and fngal infections, and this resin can be sed for varnishes and adhesives! -onifers are evergreens! ! 7ist the common characteristics of seeds plants! 1hey have vasclar tisse and se seeds to reprodce! 'n addition, they all have body plans that inclde leaves, stems, and roots! 3ost seed plants live on land! Seed plants face many challenges, inclding standing pright and spplying all their cells .ith .ater and food! +! -ontrast bet.een dicots and monocots, the t.o classes of 4o.ering plants! 3ONO-O1S $mbryo .ith single cotyledon Pollen .ith single frro. or pore ;lo.er parts in mltiples of three 3ajor leaf veins parallel
"'-O1S $mbryo .ith t.o cotyledons Pollen .ith three frro.s or pores ;lo.er parts in mltiples of for or Kve 3ajor leaf veins reticlated
6! "iscss the featres of plant 4o.ering frits and seeds! ;rits are a ni5ely angiosperm featre: part of the pollinated 4o.er ripens and becomes the frit! 1.o types of frits .ith a generally di8erent mechanism of seed distribtion e%ist: dehiscent and nondehiscent frits! "ehiscent frits set the seeds free by opening of the frit that remains itself .ith the mother plant! 'n contrast, nondehiscent frits and their seeds are a dispersal nit! "ehiscent frit types are follicles, plses, pods and capsles! Nondehiscent frits are berries, drpes and nts! Seeds are normally srronded by a togh shell, the testa, that is derived from one or more integments! 't contains the endosperm, a norishing tisse! Seeds are dispersed either by self2dispersal, also called atochory, or b y allochory .hich means that e%tern factors are involved! Allochor modes of disp ersal are dispersal by .ind (anemochorys), .ater (hydrochory) or by animals (#oochory)!
Yeferences -ain, 3!"!M Shelton, 3!G! **&! 1.enty years of natral loblolly and shortleaf pine seed prodction on the -rossett $%perimental ;orest in sotheastern Aransas! Sothern Tornal of Applied ;orestry! +(&): *2+! Tmp p Galili G, Zigel T (&+)! =-hapter One=! Seed development and germination! Ne. \or: 3! "eer! 'SLN *222! Tmp p Yaven, Peter !, Yay ;ranlin $vert, and elena -rtis! &&! Liology of plants! Ne. \or, N!\!:
