4. Ancient Lineages.pdf

Ancient Lineages Introduction : non-vascular · ca. 24700 extan...

Ancient Lineages Introduction : non-vascular · ca. 24700 extant plant species for Bryophytes informal the z non-vascular plant phyla · = name mosses , liverworts and hornworts. · Simple plant body , but exhibit tremendous adaptations to a diversity of terrestrial habitats including deserts. , · Most small seldom more than I am high. , 3 Bryophyte phyla share the following characters : 1. Photosynthetic gametophytes. z Sporophyte embedded within dominant gametophyte and dependent on for /water. gametophyte nutrition. 3 Water necessary for successful sexual reproduction bryophytes often confined to moist environments. Bryophyte Diversity : Phylum Bryophyta (mosses) · Moss gametophyte mostly with leaf like structures in spirals green , arranged or whorls around central stem-like structure · Plant body anchored to substrate via rhizoids. · Gametophyte leaf-like structures analogous to true leaves in shape , colour and presence of slightly thickened. midrib · Not true leaves ! Differ in : only single cell layer thick (slightly thicker a midrib. ( no vascular tissue or stomata all cells haploid (gametophyte · Limited water transport through stemlike axis via specialised cells , but most water absorbed directly through epidermis. Habitat : · Mosses are dominant (i. t. o. species diversity + biomass) in polar regions (tundra). Many have adaptations to sustained drought but they · mosses are not , generally common in deserts. Reproduction : Multicellular gametangia develop mature gametophyte · on. · Mosses : gametangia terminal (liverworts and hornworts : gametangia inside plant ) body  Vase-shaped archegonia and club-shaped · antheridia can occur on the same Chermaphroditic) or different plants haploid cell located swollen · I in egg lowest of the archegonium portion. Many haploid (male gametes) each cells produced by antheridium · Sperm. · Sperm cells flagellate Swim (via watery medium) to archegonia. Sperm fuse with to (2n) cells produce diploid zygote · egg. Zygote divides multiple times mitosis to produce sporophyte · via a new , plant. Mature of (seta) sporophyte long central terminating · consists axis in a , swollen capsule. · Cylindral/club-shaped sporangium develops in the capsule. Distal end of capsule terminates hygroscopic peristome teeth · in in open presence of120 to release mature spores.  Closed peristome teeth covered lid/cap the which · in a , called operculum , dehisces when spores are matur e. Foot of embedded the seta permanently · is in parent gametophyte. · Sporophyte is dependent on the parent gametophyte for food / water. · Spore mother cells (2n) in undergo sporangium meiosis spores · Upon release into suitable environment , spores germinate to form new mitosis gametophyte via. 2 Phylum Hepatophyta (liverworts) · Natural phylum (monophyletic same ancestor) but include huge diversity. · Name derived from superficial resemblance of some liverworts to human liver · Smallest species miniature filament (10 5. mm long Largest has thallus (plant body) < 20 diametre · in species cm. Gametophyte is prominent, develops cuticle surrounded by · occasionally , spores thick cell walls very. Presence of these of to land adaptation. · are signs >8500 gametophyte growth form either "leafy" thallose. · species : or · Marchantia most well-known genus in SA. (A) Flattened ribbon-shaped thallus thallose be of simple · species can or structurally differentiated and complex. · Tissue differentiated into adaxial (top) Chlorenchyma and abaxial (bottom tissue storage. Topmost layers of rich · cells in for photosynthesis chloroplasts (chlorenchyma). · Adaxial epidermis punctured by that pores connect deeper chambers leading to chloren- of chyma sites gaseous exchange. · Pores always open can't , open + close like true Stomata. · Abaxial cell layers devoted to chloroplasts storage no  Liverworks also produce · a range of characteristic volatile oils stored in unique oil bodies. · Oils emit herbal smell which is off-putting to herbivores (defence mechanism Oil have potential anti- compounds · as microbial or anti-carcinogenic medicine. Archegonia develop · in radial rows on top surface of umbrella of archegoniophore. As the archegonia · develop sterile tissue , is laid down on top surface , effectively to bottom surface transporting archegonia. Mature flask-shaped of long broad archegonium consists neck , · and and , rounded base containing single egg cell. Antheridiophore less complex than archegonio- · phone. Long neck with umbrella shaped head ·. Club-shaped antheridia embedded head · in and connected to atm. via thin channels. Large small flagellate formed each antheridium · in n.o. , sperm.  Liverwort develop within sporophytes gameto- · phyte until tissue maturity. Mature sporophyte entirely dependent · on parent gametophyte. · Consist of capsule short seta and , very foot region. Seta short initially of · consists very small thin-walled cells. , Shortly · before maturity seta cells elongate , and lengthen seta up to zo x original length. · Quick elongation pushes capsule and top portion of seta through gametophyte body. Capsule dries out into · and 4 opens seg- ments to release spores. Spores released to atm · through movements of hygroscopic , non-fertile elators. · Whole spore mass pressed out of capsule within short timespan (few min). · Thick-walled spores adapted to survival in arid atm conditions (thick cell walls) · Upon germination, spores divide via mitosis into separate male + female gametophytes. · Vegetative (clonal) reproduction extremely common in liverworks. · Thallus forms cup-shaped structures known as gemmae cups. · Granular gemmae (outgrowths of thallus) within gemmae-cups are dispersed via to habitat raindrops new. · Gemmae divide via mitosis to form new gametophyte. 3 Phylum Chornworts) ! Anthocerophyta most advanced sporophyte Origin relationships uncertain · + very Possibly most similar to original land plants. · · However oldest hornwort fossils far , younger known from the Cretaceous (65-145 a) my. flat thallus Gametophyte Sporophyte linear · is a is ; and grows vertically out of the gametophyte. · Diploid zygote develops into a thin , cylindrical sporphyte with relatively small amount of sporogenous tissue (sporan- gium). Sporophyte embedded within the parent gametophyte · remains lobed foot via clearly. Basal foot surrounded by collar-like outgrowth of thallus ·.  Hornwort cells land single chloro- plants only · are unique among a plast per cell and therefore pyrenoids are present (similar to green algael. but Gametophyte thallus superficially similar to that of liverworts , · is smaller t thinner. · Thallus has limited internal differentiation but does have several , specialised characters. (follows below :) · Tight symbiosis with colonies of Nostoc cyanobacteria in cavities found on abaxial (bottom) side of thallus. · Colonies look like dense blue-green speakles when viewed from above. · Cyanobacterium fixes atmospheric N2 into ammonia , which the hornwort uses for Synthesis protein. · Hornwort provides carbohydrate-rich mucilage as energy-source for cyano- bacterium. Gametangia embedded thallus · in Develop adaxial (top) · in rows on side. Archegonia antheridia by sterile cell layers that the · and surrounded in open of water presence. Sperm chemotactically attracted to cells · egg. · Swim through water on top surface of thallus. · Hornwort sporophyte is an elongate structure sticking out of the like needle gametophyte a. · Semi-independent of the gametophyte fully photosynthetic · Lives longer than the sporophyte of the other z non-vascular phyla · Development of sporangia begins with the formation of a dome-shaped layer within topmost part of young sporophyte. Sporophyte capable of growth through · continuous of meristem the base means an intercalary at can continue to for weeks grow. Sporangium differentiates into hollow cylinder · a with a central column of sterile cells (columella). · Multicellular elaters (without spiral thickenings : pseudo-elators) develop between sporogenous mother cells. Mother cells to form haploid (n) · undergo meiosis spores. · As distal (top) end of sporophyte matures/dries out , spores released via long fissures with aid of 2 , pseudo-elators. · Fissures continue to rupture material lower down downwards as sporophyte matures.  Basal continuously at tempo meristem generates new · tissue sporophyte same as maturation further up sporophyte constantly adds new tissue at base as topmost spores released. · Spores have thick walls and are sculptured. · Hornwort sporophytes differ from those of liverworts , and are similar to those of mosses , in that they are capable of photosynthesis in outermost surface layers. Stomata also (also of present in sporophyte capsules · in moss sporophytes). Sporophyte is thus not totally dependent parent · on gametophyte for nutrition (semi-independent). sterile cells