Kingdom Plantae: Heterospory and Seed PlantsSetting the stage for pollen/seedsSlide 3Slide 4Slide 5Slide 6Slide 7HeterosporySlide 9Slide 10PlantsSeed plant featuresSeed plant groupsSlide 14Pine life cycleSlide 16Slide 17Slide 18Slide 19Slide 20Getting male and female gametophytes togetherSlide 22Slide 23The new baby sporophyteSeed has wing: wind dispersedSeed germinates and new sporophyte is on its ownSlide 27Slide 28Slide 29Gymnosperms get their chance to rule the land....Slide 31GymnospermsKingdom Plantae:Heterospory and Seed PlantsSetting the stage for pollen/seeds•Most of plants discussed so far do not have specialized gametophytes•They are homosporous plants: make one kind of meiospore.Setting the stage for pollen/seeds•Homosporous groups–Bryophyta–Hepaticophyta–Anthocerophyta–Psilophyta–SpenophytaSetting the stage for pollen/seeds•Heterosporous plants: make 2 types of meiospores. –One becomes male gametophyte and makes sperm–One becomes female gametophyte and makes eggs•Thus, make specialized spores and specialized gametophytes.Specialization occursearlier in life cycleSetting the stage for pollen/seeds•Heterosporous groups:–Some Lycophyta–Some Pterophyta–All seed plant phyla (discussed later today!).Setting the stage for pollen/seeds•Example of heterosporous plant life cycle: Selagine lla (Lycophyta)•Seen in lab #3.Setting the stage for pollen/seeds•Heterosporous plant life cycle: Selagine lla (Lycophyta)•Photos of structures.Heterospory•Note deadbeat gametophytes–Not free-living. Dependent on sporophyte–Not (very) photosynthetic–Small: microgametophyte reduced to 1 antheridium! Megagametophyte develops mostly within megaspore.Heterospory•Spores specialized–Megaspore makes megagametophyte, which makes archegonia with eggs–Microspore makes microgametophyte, which makes antheridium containing sperm.Heterospory•Valuable ideas for life on the land:–1) Gametophytes small and protected by spore walls–2) Deadbeat gametophytes fed by big strong sporophyte (gametophytes can focus on reproduction)–3) Megaspore: keep it after fertilization and feed embryo. Embryo starts development inside megaspore and protected by its walls. Lets new embryo “eat” its mother (megagametophyte): keeps energy used to make megagametophyte from being wasted–4) Microspore: disperse it through air, instead of delicate swimming sperm.Plants•Nonvascular Plants–Covered. Reproduce by spores. Gametophytes independent of sporophyte•Seedless Vascular Plants–Covered. Reproduce by spores. Gametophytes independent of sporophyte•Seed Plants–Rest of plant kingdom. Gametophytes dependent on sporophyte.Seed plant features•Have vascular tissue–Make roots, stems, leaves (megaphylls)–Some can do secondary growth in stems/roots: make new phloem and xylem and grow in diameter rather than just length•Life Cycle–Heterosporous, but spores kept by sporophyte–Gametophytes reduced, dependent on sporophyte•Male gametophyte (microgametophyte) dispersed as pollen grain (no free-swimming sperm in water)•Female gametophyte (megagametophyte) kept by sporophyte, becomes part of ovuleSeed plant groups•Gymnosperms (“gymno-” means naked, “sperm” means seed): do not make make seeds in sealed container (fruit)–Phylum Cycadophyta (cycads)–Phylum Coniferophyta (conifers)–Phylum Ginkgophyta (ginkgo)–Phylum Gnetophyta (gnetophytes)•Note all gymnosperms do secondary growth (form wood, are shrubs or trees)Seed plant groups•Angiosperms (“angio-” means container, “sperm” means seed): make seeds in sealed container (fruit)–Phylum Anthophyta (flowering plants)•Many of these are woody, but some are herbaceous (don’t do secondary growth).Pine life cycle•Pine life cycle movie (for overview)•Example of gymnosperm life cycleQuickTime™ and aCinepak decompressorare needed to see this picture.Pine life cycle–Female cone: Cone scales with ovules on themMature female coneFemalecone atpollinationstage (top)Cone scale with ovulePine life cycle•Ovule: integumented megasporangium. Megaspore mother cell does meiosis, forms meiospores, one survives & does mitosis to make female gametophyte.1234Pine life cycle•Female gametophyte has several archegonia, each with an egg.1234()()Pine life cycle•Male cone: made up of microsporophylls•Microsporangia on sporophyllsMicrosporophyllSporangium on underside of sporophyllPine life cycle•Sporangia on microsporophylls have microspore mother cells (2n), which do meiosis to make microspores (1n)•Each microspore does a couple mitotic divisions to form an immature male gametophyte (called pollen grain).Getting male and female gametophytes together•Pollen grain flies through air (wind dispersed)•Arrives at female cone micropyle (gap between integument ends), and winds up next to female gametophyte.Getting male and female gametophytes together•Now, pollen grain germinates: makes pollen tube and spermatogenous cell. Becomes mature male gametophyte.Getting male and female gametophytes together•Pollen tube penetrates into female gametophyte to find archegonium, so sperm and egg can fuse to make zygote.The new baby sporophyte•Zygote grows to embryo as ovule becomes seed–Integument (2n tissue from parent sporophyte) becomes hard protective seed coat–Female gametophyte serves as food for growing embryo.Remains of seed coat (most dissected away)Female gametophyteEmbryoSeed has wing: wind dispersed•Winged pine seed helicoptering away (most pine seeds fly this way)Seed germinates and new sporophyte is on its own•Young pine seedlingPine life cycle•Take home lessons:–1) Pollen grain is immature male gametophyte (microgametophyte)–2) Male gametophyte matures in ovule, when pollen tube and sperm cell made. Entire male gametophyte is just a few cells.–3) Ovule contains megasporangium. Meiosis produces megagametophyte, which makes archegonia, still kept in megasporangium.Pine pollen grainPine life cycle•Take home lessons:–4) Fertilization takes place and embryo digests female gametophyte.–5) Seed is baby plant (embryo), in box (seed coat from parent sporophyte tissue), with its lunch (female gametophyte)!.Pine life cycle•Advantages of making seeds and pollen:•1) Male gametophyte (immature) small, protected by microspore wall, flies through air to female gametophyte•2) No swimming sperm. Male gametophyte delivers sperm to female gametophyte protected by ovule in