Bio44 L10 Early Plants.ppt - Claremont Colleges

3/1/2011Kingdom Plantae Plant or land plants Multicellular eukaryotic organismscomposed of cells having plastids Primarily live on land Evolved from green algal ancestors thatlived in aquatic habitats Distinguished from modern algal relativesby adaptations to terrestrial life SectionS i 4Professor Donald McFarlaneLecture 10 Plants:Colonization of the Land2Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.StreptophytesLand plants (kingdom Plantae) (embryophytes)Vascular plants (tracheophytes)EuphyllophytesAncestrySeed plants (spermatophytes)AngiospermsGinkgoConifers ytesMossesHornwortsComplex charophyceansOther green algaeSimple vascular plantsBryophytes(nonvascular plants)Green algae Probably originated from a photosyntheticprotist ancestor having a relativelycomplexpbodyy Either Chara or Coleochaete are modernprotists most closely related to ancestry ofland plantsFlowers,fruits,endospermin seeds248PermianOvules, lions of years ago (mya)290CarboniferousEuphylls (megaphylls)354417Filament of cells with side branchesLignin in walls of water-conductingcells; cutin common on epidermis;stomata common on plant surfaces;dominant sporophyte generation;true roots, stems, leaves443490Cambrian543PROTEROZOICSporic life cycle, embryo, sporopollenin-walled spores, tissue-producingapical meristem, gametangia, sporangia, xyloglucans in cell wallPlasmodesmata, plant-specific features of cell division, eggs and spermChlorophyll a and b, starch produced in plastids2500Common protist ancestorKEYCritical innovationsa: Roland Birke/Phototake; b: The McGraw-Hill Companies, Inc./Linda Graham, photographer; c-e: Lee W. Wilcox; f: B. Runk/S. Schoenberger/GrantHeilman Photography; g: Ed Reschke/Peter Arnold; h: Patrick Johns/CORBIS; i: Bob Evans/Peter Arnold; j: Wolfgang Kaehler/Corbis; k: FredBruemmer/Peter Arnold; l: Gallo Images/Corbis341

3/1/2011 Distinctive feature of land plantsComplexcharophyceansshare severalderived traits withland plants Represent early adaptations to landBodies composed of 3D tissuesIncreased ability to avoid water lossPlasmodesmataSexualreproduction usingegg and smallersperm Tissues arise from apical meristems at growing tipsAble to produce thick, robust bodiesTissues and organs with specialized functionsDistinctive reproductive featuresAlternation of generationsDry air resistant reproductive cellSpecialized structures to generate, protect, and dispersereproductive cells510 plant rts – HepatophytaMosses – BryophytaHornworts – AnthocerophytaLycophytes – LycophytaPteridophytes – PteridophytaCycads – CycadophytaGinkgos – GinkgophytaConifers – ConiferophytaGnetophytes – GnetophytaAngiosperms – AnthophytaInclude liverworts, hornworts, and mossesEach forms a monophyletic phyla Share common structuralstructural, reproductiveand ecological features Models of earliest terrestrial plants 782

3/1/2011Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sporangium Sporophyte Gametophyte Bryophytes display features absent fromcharophycean algae but present in plantsLikely early adaptations to landCharophycean algae display a zygotic life cyclewith a one cell diploid zygoteBryophytes and other plants exhibit a sporic lifecycle with alternation of generationsDiploid, spore-producing sporophyte generationHaploid, gamete-producing gametophyte generation(mniumSEM): Eye of Science/Photo Researchers910Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.KEYSingle-celleddiploid (2n)zygotehaploiddiploidMulticellular Spermhaploid MitosisKEYHaploidDiploidClarophycean “algae”Haploid sporesMeiosis11New:multicellulardiploid (2n)sporophyte123

3/1/2011Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.SpermFertilizationAdaptations to life on landMulticellular haploid(n) gametophyteSingle-celleddiploid (2n)zygoteEggCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.SporesSporedispersal tipMeiosisMulticellular diploid sporophyte generationadvantageous because it allows a singleplant to disperseppwidelyy byy usingg meiosisto produce numerous, genetically variablehaploid spores Each spore has the potential to grow intoa gametophyte Mitosis(a) Zygotic life cycle of charophyceansEvolutionaary changeSporophyteKE ellularhaploid (n)gametophyteEgg Lee W. WilcoxSingle-celleddiploid ploid (2n)sporophyte(b) Sporic life cycle of early plants13Gametophytes Sporophytes Role to produce haploid gametesProduced by mitosisGametangia protects developing gametes fromd i outt anddryingd microbiali bi l attacktt k Antheridia – round or elongate gametangia producingspermArchegonia – flask shaped gametangia enclosing anegg Sperm swim to egg and fuse to form diploidzygoteZygotes grow into sporophytes1415 Matrotrophy – zygotes remain sheltered and fedwithin gametophyte tissueEmbryophytes – all land plants havepembryosymatrotrophicWhen mature, spores are produced in protectiveenclosures known as sporangiaPlant spore cell walls contain sporopollenin tohelp prevent cellular damageDuring evolution, plant sporophytes becomelarger and more complex164

3/1/2011Distinguishing bryophyte features Gametophytes dominant generationAs opposed to dominant sporophytegeneration in other plants Sporophytes are dependent ongametophtye – small and short livedAs opposed to independent, large and longlived in other plants Nonvascular or lacking tissues forstructural support and conduction found inother plants (vascular plants)1718 Lycophytes and pteridophytesPteridophytes – about 12,000 species ofhorsetails, whisk ferns and other fernsCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Vascular plantsthat do not produceseeds Lycophytes- morenumerous andlarger in the pastbut now about1000 relativelysmall species SporangiaStemSmall leaves Lee W. Wilcox19205

3/1/2011Roots, stems and leaves Diverged prior to the origin of seeds Seedless vascular plants StemsContain vascular tissue and produce leavesand sporangiaContain phloem and xylem (containstracheids and lignin)Lycophytes, pteridophytes and seedproducing plants are vascular plants ortracheophytes Possess tracheids for water and mineralconduction and structural supportVascular tissues occur in the major plantorgans: stems, roots, and leavesRootsSpecialized for uptake of water and mineralsfrom the soil LeavesPhotosynthetic function21Adaptations That Foster Stable InternalWater ContentLife cycleCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Vascular tissue Waxy cuticle present onmost surfaces of vascularplant sporophytesCutin found in cuticle thathelps prevent pathogenattackWax prevents dessicationStomata are pores thatopen and close to allowgas exchange whileminimizing water loss22 Stomate Cuticle120 mm(a) Stem showing tracheophyte adaptationsStomata(b) Close-up of stomataa: The McGraw-Hill Companies, Inc./Linda Graham, photographer; b: Lee W. Wilcox23Lycophyte and pteridophyte reproduction islimited by dry conditions, as is the case forbryophytesHowever, if fertilization occurs, lycophytes andpteridophytes can produce many more sporesdue to their larger sporophyte generationVascular plant sporophytes are dependent uponmaternal gametophytes for only a short time duringearly embryo developmentStems of vascular plant sporophytes are able toproduce branches, forming relatively large adultplants having many leaves246

3/1/2011Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Sporophyte(sporophyte): Barrett & MacKay Photography; Companies, Inc. Permission required for reproduction or display257

3/1/2011 6 Diverged prior to the origin of seeds Seedless vascular plants Lycophytes, pteridophytes and seed-producing plants are vascular plants or 21 producing plants are vascular plants or tracheophytes Possess tracheids for water and mineral conduction and structural support