1.Evolutionary History of Plants

2. Evolutionary History of Plants Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.flowers, double fertilization, endosperm, fruitcommon ancestorFlowering plants Seedseedsmegaphylls VascularGymnosperms vascular tissue SeedlessFerns and allies apical growthmicrophyllsembryo protectionBryophytesMosses Hornwortscommon green algal ancestorLiverwortsNonvascularLycophytesCharophytes 550500450 400 350 Million Years Ago (MYA)300250PRESENT5 3. Gametophyte Mitosis Mitosis n n n Spore n Gamete MEIOSISApical meristem of shootDeveloping leavesFERTILIZATION2n Zygote Haploid DiploidMitosis Sporophyte1 Alternation of generations Archegonium with egg2 Apical meristemsAntheridium with spermSporangiumSpores1 m 3 Multicellular gametangia4 Walled spores in sporangia 4. Alternation of Generations Life cycle involves alternation of generations Sporophyte (2n): Multicellular individual that produces spores bymeiosis Spores is haploid cell that will become gametophyte Gametophyte (1n): Multicellular individual that produces the gametes Gametes fuse in fertilization to form zygote Zygote is a diploid cell that becomes a ssporophyte 7 5. Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.sporesG a m e t o p h y t eseedseedsporesSrootsp orootsr orhizoidsrootsp hrhizoids(n)y tMossFernGymnospermAngiosperme(2n)8 6. Other Terrestrial Adaptations Vascular tissue transports water and nutrients to thebody of the plantCuticle provides an effective barrier to water loss Stomata bordered by guard cells that regulateopening, and thus water loss9 7. Nonvascular Plants: Bryophytes Nonvascular plants (bryophytes) Lack specialized means of transporting water andorganic nutrientsDo not have true roots, stems, and leaves Dependent sporophyte consists of a foot, stalk andsporangiumGametophyte is dominant generation Produce eggs in archegonia Produce sperm in antheridia Sperm swim to egg infilm of water to make zygote10 8. Nonvascular Plants Hornworts (phlym Anthocerophyta) have smallsporophytes that carry on photosynthesisLiverworts (phylum Hepatophyta) have eitherflattened thallus or leafy appearanceMosses (phylum Bryophyta) usually have a leafyshoot, although some are secondarily flattened Can reproduce asexually by fragmentation 11 9. Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.4. The sporophyte: The mature sporophyte has a foot buried in female gametophyte tissue, a stalk, and an upper capsule (the sporangium), where meiosis occurs and spores aredeveloping sporophyte3. The zygote: The zygote and developing sporophyte are retained within the archegonium.capsule5. The spores: When the calyptra and lid (operculum) of a capsule fall off, the spores are mature. One or two rings of teeth project inward from the margin of teeth the capsule. The operculum teeth close the opening, except when the weather is dry.Sporangiumcalyptra Mitosisstalk Sporophytezygote diploid (2n) FERTILIZATION2. Fertilization: Flagellated sperm produced in antheridia swim in external water to archegonia, each bearing a single egg.spermMEIOSIShaploid (n) Sporesfoot (n)eggMitosis Archegonia buds ProtonemaAntheridia 1. The mature gametophytes: In mosses, the leafy gametophyte shoots bear either antheridia or archegonia, where gametes are7. The immature gametophyte: A spore germinates into a male or female protonema, the first stage of the male and the female gametophytes.Gametophytesrhizoids (Top): Heather Angel/Natural Visions; (Bottom): Bruce Iverson126. Spore dispersal: Spores are released when they are most likely to be dispersed by air currents. 10. Seedless Vascular Plants: Lycophyta Club Mosses (phylum Lycophyta) Typically, branching rhizome sends up short aerialstemsLeaves are microphylls (have only one strands ofvascular tissue)Most likely evolved as a simple side extensions of thestemSporangia occur on surfaces of sporophylls 13Grouped into club-shaped strobili 11. Seedless Vascular Plants Roots evolved as lower extensions of the stem todays lychophytes, also called club mosses, includethree groups of 1,150 species: o Ground pines (Lycopodium) o Spike mosses (Selaginella) o Quillwort (Iseotes)14 12. Seedless Vascular Plants: PteridophytesIncludes Ferns and their Allies (horsetails andwhisk ferns)Have megaphylls (broad leaves) allow plants to effectively collect solar energy Produce more food and the possibility of producing more offspring than plants without megaphyllsHorsetails rhizome produces tall aerial stems Contains whorls of slender, green branches Small, scale like leaves also form whorl at the joint15 13. Microphylls and Megaphylls single strand of vascular tissue a. Microphyllbranched vascular tissue MegaphyllOne branch began to dominate the stem system.branched stem system b. Megaphyll evolution process16The side branches flattened into a single plane.Tissue filled in the spaces between the side branches.megaphyll leaf 14. Ferns Whisk Ferns (phylum Psilotophyta) Branched rhizome has rhizoids (extensions) Mutualistic mycorrhizal fungus helps gather nutrientsFerns (phylum Pterophyta) Large conspicuous fronds divide into leaflets Dominant sporophyte produces windblown spores17 15. Figure 29.13-3Key Haploid (n) Diploid (2n) MEIOSISSpore dispersalSpore (n)Rhizoid Underside of mature gametophyte (n)SporangiumSporangiumAntheridiumYoung gametophyteMature sporophyte (2n)SorusNew sporophyteSperm Archegonium EggZygote (2n)FERTILIZATIONGametophyteFiddlehead (young leaf)1 m In contrast with bryophytes, sporophytes of seedless vascular plants are the larger generation, as in familiar ferns 16. Seed Plants Seed plants are the most plentiful plants in thebiosphereSeed coat and stored food allow an embryo to surviveharsh conditions during long period of dormancyHeterosporous Drought-resistant pollen grains Ovule develops into seed 19 17. Gymnosperms Gymnosperms have ovules and seeds exposed on the surface of sporophylls Conifers Conifers, as well as other gymnosperm phyla, bear conesTough, needlelike leaves of pines conserve water with a thick cuticle and recessed stomataConsidered a soft wood because it consist primarily of xylem tissue (water flow) Cycads Large, finely divided leaves that grow in clusters at the top of the stemPollen and seed coats on separate plants Ginkgoes Dioecious: Some trees producing seeds and others producing pollen Gnetophytes 20None have archegonia 18. Figure 30.3-3If a pollen grain germinates, Immature it gives rise to a pollen tube ovulate cone that discharges sperm into the female gametophyte within the ovule Female gametophyte (n)Integument (2n) Spore wallMicropylePollen grain (n)(a) Unfertilized ovuleSpore wallEgg nucleus (n)Megaspore (n)Megasporangium (2n)Seed coatDischarged sperm nucleus (n) Pollen tube Male gametophyte (n)(b) Fertilized ovuleFood supply (n) Embryo (2n) (c) Gymnosperm seedA seed is a sporophyte embryo, along with its food supply, packaged in a protective coat 19. Angiosperms Ovules are always enclosed within diploid tissues Two classes of flowering plants 22Monocotyledones (Monocots) 1 cotyledon Eudicotyledones (Dicots) 2 cotyledons 20. Monocots vs Eudicots Number of cotyledons -- The cotyledons are the "seed leaves" produced by the embryo. They serve to absorb nutrients packaged in the seed, until the seedling is able to produce its first true leaves and begin photosynthesis. The number of cotyledons found in the embryo is the actual basis for distinguishing the two classes of angiosperms, and is the source of the names Monocots ("one cotyledon") and Eudicots ("two cotyledons"). Number of flower parts -- Monocot flowers = divisible by three, usually three or six. Dicot flowers = multiples of four or five This character is not always reliable, however, and is not easy to use in some flowers with reduced or numerous parts. Leaf veins Monocots = veins which run parallel the length of the leaf. Eudicots, = numerous veins which reticulate between the major ones. Stem vascular arrangement -- Vascular tissue occurs in long strands called vascular bundles. These bundles are arranged within the stem of eudicots to form a cylinder, appearing as a ring of spots when you cut across the stem. In monocots, these bundles appear scattered through the stem, with more of the bundles located toward the stem periphery than in the center. Root development -- In most eudicots (and gymnosperms) the root develops from the lower end of the embryo, from a region known as the radicle. The radicle gives rise to an apical meristem which continues to produce root tissue for much of the plant's life. By contrast, the radicle dies in monocots, and new roots arise from nodes in the stem. These roots may be called prop roots when they are clustered near the bottom of the stem. Secondary growth Gymnosperm and eudicots increase their diameter through secondary growth, producing wood and bark. Monocots (and some dicots) do not produce wood. 21. Figure 30.13eaMonocot CharacteristicsEudicot Characteristics EmbryosTwo cotyledonsOne cotyledon Leaf venationVeins usually netlikeVeins usually parallel StemsVascular tissue scatteredVascular tissue usually arranged in ring 22. Figure 30.13ebMonocot CharacteristicsEudicot Characteristics RootsTaproot (main root) usually presentRoot system usually fibrous (no main root) PollenPollen grain with one openingPollen grain with three openingsFlowersFloral organs usually in multiples of threeFloral organs usually in multiples of four or five 23. The FlowerPeduncle (flower stalk) expands at tip into a receptacle Bears sepals, petals, stamens, and carpels, all attached to receptacle inwhorls Each stamen consists of an anther and a filament (stalk)Carpel has three major regions Ovary swollen baseStyle elevates stigmaStigma sticky receptor of pollen grainsfruit Calyx (collection of sepals) protects flower bud before it opens Corolla (collection of petals) 26 24. Figure 38.2bAntherGerminated pollen grain (n) (male gametophyte) Ovary Ovule Embryo sac (n) (female gametophyte)Pollen tubeEgg (n)FERTILIZATIONSperm (n) KeyZygote (2n)Mature sporophyte plant (2n)Haploid (n) Diploid (2n)(b) Simplified angiosperm life cycleGerminating seed SeedSeedSimple fruitEmbryo (2n) (sporophyte) 25. Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.StamenCarpel stigmaantherstylefilamentovary ovule 7. The sporophyte: The embryo within a seed is the immature sporophyte. When a seed germinates, growth and differentiation produce the mature sporophyte of a flowering plant.The ovules: In an ovule (megasporangium) within an ovary, meiosis produces four megaspores.Mitosis stigma fruit (mature ovary)Sporophyte 1. The stamen: An anther at the top of a stamen has four pollen sacs. Pollen grains are produced in pollenseed (mature ovule) 6. The seed: The ovule now develops into the seed, which contains an embryo and food enclosed by a protective seed coat. The wall of the ovary and sometimes adjacent parts develop into a fruit that2. The pollen sacs: In pollen sacs (microsporangia) of the anthe ,r meiosis produces microspores.Pollen sac (microsporangium)Ovule (megasporangium)The carpel: The ovary at the base of a carpel contains one or more ovules. The contents of an ovule change during the flowering plant life cycle.seed coat embryo endosperm (3n)styleovary AntherSeed diploid (2n)FERTILIZATIONMEIOSIShaploid (n) (Mature male gametophyte)tube cellovule wall polar nuclei spermpollen tube spermegg tube cell nucleusMicrosporesMegasporesovule wall antipodals polar nuclei eggto mipollen tubegenerative cellsisPollinationto midegenerating megasporessis5. Double fertilization: On reaching the ovule, the pollen tube discharges the sperm. One of the two sperm migrates to and fertilizes the egg, forming a zygote; the other unites with the two polar nuclei, producing a 3n (triploid) endosperm nucleus. The endosperm nucleus divides to formMEIOSISPollen grainsynergids Embryo sac (mature female gametophyte) 4. The mature male gametophyte: A pollen grain that lands on the carpel of the same type of plant germinates and produces a pollen tube, which grows within the style until it reaches an ovule in the ovary. Inside the pollen tube, the generative cell nucleus divides and produces two nonflagellated sperm. A fully germinated pollen grain is the mature28The mature female gametophyte: The ovule now contains the mature female gametophyte (embryo sac), which typically consists of eight haploid nuclei embedded in a mass of cytoplasm. The cytoplasm differentiates into cells, one of which is an egg and another of which contains two polar nuclei.3. The microspores: Each microspore in a pollen sac undergoes mitosis to become an immature pollen grain with two cells: the tube cell and the generative cell. The pollen sacs open, and the pollen grains are windblown or carried by an animal carrier, usually to other flowers. This is pollination. The megaspores: Inside the ovule of an ovar y , three megaspores disintegrate, and only the remaining one undergoes mitosis to become a female gametophyte. 26. Figure 30.2 PLANT GROUP Mosses and other nonvascular plantsGametophyte Dominant SporophyteFerns and other seedless vascular plantsSeed plants (gymnosperms and angiosperms)Reduced, independent (photosynthetic and free-living)Reduced (usually microscopic), dependent on surrounding sporophyte tissue for nutritionReduced, dependent on Dominant gametophyte for nutritionDominant GymnospermSporophyte (2n) Sporophyte (2n)Microscopic female gametophytes (n) inside ovulate coneGametophyte (n)AngiospermMicroscopic female gametophytes (n) inside these parts of flowersExampleGametophyte (n)Microscopic male gametophytes (n) inside pollen cone Sporophyte (2n)Microscopic male gametophytes (n) inside these parts of flowers Sporophyte (2n) 27. Bryophytes Gametophyte dominant; sporophyte dependent; gametophyte independentSeedless vascular plants Sporophyte dominant; sporophyte initially dependent; gametophyte independentSeed plants Sporophyte dominant; sporophyte independent; gametophyte dependent & microscopicGymnosperms Gametophytes develop inside cones Angiosperms Gametophytes develop inside flowers 28. Tutorvista.com 29. Pearson The Biology Place - http://www.phschool.com/science/biology_place/biocoach/plants/tissue.html 30. Ground Tissue Parenchyma cells Have thin and flexible primary walls Lack secondary walls Are the least specialized Perform the most metabolic functions Retain the ability to divided and diffrentiateCollenchyma cells help support young parts of the plant shoot They have thicker and uneven cell walls The cells provide flexible support without restraining growthSclerenchyma cells are rigid because of thick secondary walls strengthened with lignin They are dead at functional maturity There are two types:1. Sclereids are short and irregular in shape and have thicklignified secondary walls 2. Fibers are long and slender and arranged in threads 31. Roots A root is an organ with important functions: 1. anchoring the plant 2. Absorbing minerals and water 3. Storing carbohydrates In most plants, absorption of water and mineralsoccurs near the root hairs, where vast numbers of tiny root hairs increase the surface area 32. Figure 35.14Epidermis Cortex Endodermis Vascular cylinder100 m (a) Root with xylem and phloem in the center (typical of eudicots) 50 mPericycle Core of parenchyma cells Xylem PhloemEndodermis Pericycle Xylem Phloem100 m (b) Root with parenchyma in the center (typical of monocots) Key to labels Dermal Ground Vascular 33. Figure 35.13CortexVascular cylinderEpidermisRoot hairZone of differentiationKey to labels Dermal Ground VascularZone of elongationZone of cell division (including apical meristem) Root capMitotic cells100 m 34. Most eudicots and gymnosperms have a taprootsystem, which consists of:A taproot, the main vertical root Lateral roots, or branch roots, that arise from the taprootMost monocots have a fibrous root system, whichconsists of:Adventitious roots that arise from the stems or leaves Lateral roots that arise from adventitious roots 35. Stems A stem is an organ consisting of An alternating system of nodes, the point at which leaves are attached Internodes, the stem segments between nodes An axillary bud is a structure that has the potential to form a lateralshoot, or branch An apical bud, or terminal bud, is located near the shoot tip andcauses elongation of a young shoot Apical dominance helps to maintain dormancy in most axillary buds Many plants have modified stems (eg. Rhizoids, bulbs, stolons, tuber) 36. The vascular tissue of a stem or root is collectivelycalled the steleIn angiosperms the stele of the root is a solidcentral vascular cylinderThe stele of stems and leaves is divided intovascular bundles, strands of xylem and phloem 37. Figure 35.17PhloemXylemSclerenchyma (fiber cells)Pith EpidermisCortex Vascular bundleGround tissueGround tissue connecting pith to cortex1 mm(a) Cross section of stem with vascular bundles forming a ring (typical of eudicots)Epidermis Key to labels Dermal Ground VascularVascular bundles1 mm(b) Cross section of stem with scattered vascular bundles (typical of monocots) 38. Seeds Seed coat, or testa can be impenertrable, especially in long dormancy need Cotyledons are leaf-like structures in the seed that provide nourishment while the seed germinates Radicle = embryonic root Plumule = seed shoot Epicotyl = portion of stem above the point where the stem is attached to the cotyledon Hypocotyl = portion of stem below the cotyledon Endosperm = source of nutrients Hillum = point of attachment of seed to the ovary wall Micropyle = small opening near hillum 39. Secondary growth increases the diameter of stems and roots in woody plants Secondary growth occurs in stems and roots ofwoody plants but rarely in leaves The secondary plant body consists of the tissues produced by the vascular cambium and cork cambium Secondary growth is characteristic of gymnosperms and many eudicots, but not monocots 40. Lateral meristems add thickness to woody plants,a process called secondary growth There are two lateral meristems: the vascular cambium and the cork cambium The vascular cambium adds layers of vascular tissue called secondary xylem (wood) and secondary phloem The cork cambium replaces the epidermis with periderm, which is thicker and tougher 41. Figure 35.11Primary growth in stems Epidermis Cortex Primary phloemShoot tip (shoot apical meristem and young leaves)Axillary bud meristemPrimary xylem Pith Vascular cambium Secondary growth in stems Lateral Cork meristems cambium Cork cambium PeridermCortex Primary phloemRoot apical meristemsSecondary phloemPith Primary xylemSecondary xylemVascular cambium