1Gymnosperms:needles and conesL5 S1GymnospermsStage One: Becoming multicellularStage Two: Developing sporangia Occurred in waterEnables specialized tissues to developEnables dispersal on landStage Three: Developing a large sporophyteConfers competitive advantageProvides perennial spore productionStage Four: Removing dependence of fertilization on a film of waterEnables survival in dry environmentsEvolutionary stages necessary for plants to colonize landL5 S2Gymnospermsnakedseedand the conifers!!Four major living groupsCycas bougainvilleanaCycadsFemale coneMale coneCarbon-14 dating ofCarbon-14 dating ofthe largest plantsthe largest plantshave shown thathave shown thatsome individuals aresome individuals areover 1500 years old.over 1500 years old.Ginkgo, theMaiden HairTreeWelwitschia groupL5 S3Plant of the Day - Ginkgo bilobaIllustration in Pen TsaoKang Mu of Ginkgo withseeds (1578)The only surviving species of a diverse group originatingin the Permian, closely related fossils 200m ybpMotile male spermGrows “spontaneously” near Changhua Hsien in TaiwanGinkgo biloba extract (Gbe) and two ingredients,bilobalide and ginkgolide B, are presented to the CSWGas part of a review of botanicals being used as dietarysupplements in the United States. Deregulation ofbotanicals now permits Gbe to be sold as a dietarysupplement to a willing public eager to "improve brainfunctioning" or "promote radical scavenging activity".L5 S4Medicinal!!Ginkgo biloba- the wonder drug!What, ginkgo? I thoughtthat was just for old peoplewho couldn't keep a train ofthought? Nope, you'rewrong. Ginkgo can be avery beneficial herb tobodybuilders as well.http://www.teenbodybuilding.com/gingko.htmToday everyone is lookingfor a way to enhance his orher workouts. So what canyou do, well, take someGinkgo Biloba.PangeaCarboniferous360 to 286 myaIn the Permian (286-245 mybp)the land masses came togetherand formed a large continentcalled PangeaContinental type climatesdeveloped with dry periods orseasonal rains. These can beseasonal and may be calledmonsoonsGymnosperms show adaptationsto drier conditions inreproduction and vegetativegrowthL5 S521. Airborne male gametophyte (pollen) carried by wind to the femalegametophyte. The fertilized egg is retained and protected by thesporophyte.2. Production of a durable seed consisting of a protective seed coat, asource of nutrition and an embryo sporophyte all in one package.3. Seed plants have wood producing tissue well developed for waterconduction and support. This enables plants to grow tall and out-competeneighbors.Conifer adaptations for harsh environmentsReproductiveVegetativeXerophyte: a plant that can live where water supply is scanty or there isphysiological droughtL5 S64. Conifer needles have a thick cuticle and few stomata thatminimizes water loss and generally a single vascular strand thatminimizes water supply.Zion CanyonPinus monophyllumTap roots stretch down40 or more feet into thesoil.Very slow growth rates: a 6-10 inch diameter tree, 10feet tall will be 80-100 yearsold.The Pinyon pine-Juniper communityL5 S7White spruce and the Brooks Range, AlaskaPotential for Physiological Drought –cold soils and warm airL5 S8The conifer life cyclesection through one ovule (the red“cut” in the diagram to the left)ovulesurface view of onecone scale (housestwo ovules)section through apollen-producingsac (red cut)surface view of onecone scale (houses apollen-producing sac )meiosismeiosisfertilizationzygotematuresporophyteseedingpollen tubesperm-producingcell(view inside an ovule)eggsWindpollinationMicrospores form,develop into pollen grains.Megaspores form,one develops into afemale gametophyte.seedGermination of pollen grain (the malegametophyte). Sperm nuclei form asthe pollen tube grows toward the egg.Diploid StageHaploid StageyoungfemaleconeseedcoatmaleconeEmbryo, 2nFemale gametophyteFig. 24.18, p. 425Any questions?Nutritivematerial, nL5 S9Two eggs – but only onewill become a zygote.Redundancy of this typeis quite common.Pictures of male cone and pollenMicrosporangiumPollen grainsMale coneContinuingvegetative shootAir sacsGenerative cellnucleusPollen cell nucleusPineL5 S10Pictures of female coneFemale coneLongitudinal section through ovulate coneSingle scale (sporophyllOvuleMegagametophyteFemale gametophyteArchegoniaEggOnly one eggbecomes aseedL5 S1133. Seed plants have wood producing tissue welldeveloped for water conduction and support. Thisenables plants to grow tall and out-competeneighbors and persist for long periods. Conifers areamong the tallest plants known ~100 m.VegetativeConifer adaptations for drierenvironmentsL5 S124. Conifer needles have a thick cuticle and fewstomata that minimizes water loss and generally a singlevascular strand that minimizes water supply.Cross section of a young pine stemL5 S13In conifers it consists of:tracheids that conduct water upwards, are long in thevertical direction, and have bordered pits that canshut when a tracheid collapses under low waterpotentialray cells running horizontally through the xylemand are composed mainly of parenchyma andsome tracheids.Secondary xylem is a complex tissueL5 S14It conducts water, stores water, and provides supportCambium and secondary xylem of a coniferCambium and secondary xylem of a coniferCambiumRay initialsLate woodEarly woodRaysTracheids withbordered pitsEsau 1965Cambium and secondaryxylem of a coniferDirection of growthL5 S15Recall how thecambiumproduces xylemcells. Thisdrawing showswhat those cellsdifferentiate to.http://www.uri.edu/artsci/bio/plant_anatomy/43.htmlTangential longitudinal sectionTracheids and rays, pineL5 S16PitsBordered pitsas seen in face view (left) and in side view (right).http://www.uri.edu/artsci/bio/plant_anatomy/images.htmlThe torus at the center of the bordered pitmoves and seals the pit when a tracheid aspiratesCircular bordered pits of pine tracheidsRadiallongitudinalsectionL5 S174Transverse sectionRayEpithelial cellTracheidXylary resin duct in PinusL5 S18Resin production slows the spread of bark beetles and fungiConifer needlesThe site of photosynthesisExchange between the needle and theatmosphere of CO2 (into the needle) andwater vapour (out of the needle).Why is water loss inevitable?Gaseous exchange takes place through a water film onthe cells inside of the needle and is regulated by stomataL5 S19Leaf cross section of Taxus (yew)The mesophyll is differentiated into palisade and spongy layersThe needle is broad, but still