Bryophyte Divisions • Three divisions –Hepatophyta (liverworts) –Anthocerophyta (hornworts) –Bryophyta (mosses) botit.botany.wisc.edu Beatific Bryophytes nobuosubaru.blogzine.jp Seta www.hiddenforest.co.nz Common Characteristics Homospory • Motile sperm • All bryophytes homosporous • Gametophyte thallus most prominent • Produce 1 kind of spore generation, not sporophyte • Spore develops into gametophyte – Thallus = plant tissue undifferentiated into a • Gametophyte produces both antheridia leaf, stem or root (sperm) and archegonia (eggs) • Most leaves lack cuticle – For absorption • No true leaves, stems or roots – General lack of vascular tissue – But see mosses, … 1 Bryophyte Phylogenies But Not a Natural Group! Vascular LiverwortMoss Hornwort plants Vascular • Paraphyletic Hornwort Liverwort Moss plants – Some, but not all, descendents of a common ancestor – In other words, what other people thought was correct was, in fact, wrong Vascular Liverwort Hornwort Moss plants – Based on an old taxonomy Vascular MossHornwort Liverwort plants Rhizoids sterile Antheridia jacket • Roots – Absorption – Anchorage fertile – Vascular tissue cells • Rhizoids (sperm) – Anchorage – Minimal or no absorption – No vascular tissue! • Rhizomes – Underground stem – Vascularized, with stem (not root) pattern 2 Archegonia Hornworts •Simplest gametophyte of all bryophytes •Small, flat thallus sporophyte neck gametophyte egg cell venter Sporophyte Sporophyte s • Contains true stomata p Sporangium o – Gas exchange (capsule) r o • Under favorable conditions may outlive p h gametophyte Foot y – Foot acts as root t e – Conducting tissue may develop at Gametophyte sporangium base •Foot supplies nutrients via transfer cells – Unusual condition of free-living •Embedded in gametophyte sporophyte! 3 Anthoceros Hornwort Spermatozoid Capsule splits (sporangium) Liverworts Liverworts Using Marchantia as an example • Gametophyte often ribbon-like – Thallose or leafy • Rhizoids • Sporangia with 4 valves • Capsule with elaters – Specialized, thickened cells – Dispersal • Examples: Riccia & Marchantia • Gametangia buried in deep, lengthwise depressions on upper surface of thallus 4 Sexual reproduction: Asexual reproduction Archegoniophores • Marchantia is dioecious (separate male & female plants) •Form on upper surface. •Contain gemmae (small green disks of tissue) Archegoniophore: structure bearing archegonia •Raindrops break them free of cup, & these can turn into gametophytes NOT sporophyte tissue!!!! Marchantia Sporophyte Marchantia Antheridiophores Antheridiophore: structure bearing antheridia 5 Spermatozoid Marchantia Life Cycle Mosses Bryophyta: Mosses 3 classes www.kib.ac.cn sporophyte • Andreaeopsida – Lantern, Granite mosses gametophyte Andreaea • Sphagnopsida – Peat mosses Maire Smith Sphagnum • Bryopsida – True mosses Polytrichum 6 Gametophytes Protonemal Phase • 3 Phases – Protonemal phase • Creeping, filamentous – Bud phase phase – Leafy phase (“phyllids”) • Spores initially dormant – Water + light cause growth – Protonema comes out of spore – Growth is directed towards red light Bud Phase Vascular Plants? • Some protonemal cells • Some mosses have hydroids & leptoids develop into a mass of • Not the same as xylem & phloem cells called a bud • One bud cell functions as the tip of a caulid, controlling direction of further cell division • Each bud develops into a mature gametophyte • Rhizoids grow downward from bud 7 Hydroids Leptoids • Hydroids have no lignin • Primitive sieve elements? • Very slow translocation of water • Degenerate, inactive nuclei • Limited distribution in plant • Many plasmodesmata in end walls • Mosses can remain dry for a long time, – Plasmodesmata connect cells yet come back to life when wetted • Nearby parenchyma tissue may act as – Up to 20 years in drought-tolerant species, companion cells yet come back to life within 4-24 hours! – Details when we cover anatomy – Try it! Get some moss, let it dry for a few – Companion cells (higher plants) help weeks or longer, then wet it load/unload sugars, etc. Asexual reproduction Sexual Reproduction • Gemma cups (splash cups) • Gametangia produced at main caulid apex • Monoecious or dioecious • Clonal • Apparent independent of light – Protonema can produce more – Soil pH, air temp., etc. buds • Antheridial heads • Phyllid tissue in wet soil – Antheridia elongate may produce protonemal – Outer sterile jacket usually contains chloroplasts strands – Sperm have 2 flagella • Rhizoids can produce buds • Archegonial heads. (sometimes) – Often retain a layer of water (phyllids aid in this) – Any sperm that land can swim on in 8 Moss Sporophyte Moss Sporophyte • Foot, seta and capsule • Mature seta and capsules contain: • Old archegonium increases in size, – epidermis of cuticle becomes the calyptra – stomata – Acts as temporary – thick-walled steroids (small, thick-walled protective covering over parenchyma cells) sporangium – a cortex region • Operculum covers – central strand of conducting tissue sporangium opening • Can produce 10-50% of • Up to 50 million spores photosynthesis needs per sporangium – Rest from gametophyte Dispersal: Peristome Moss Life Cycle • Calyptra falls off • Operculum shed • Peristome teeth attached to annulus peristome teeth annulus 9 What good is it? Sphagnum • Sphagnum have large, empty, clear cells in epidermis that fill with water (via a pore) & serve as reservoir • Worldwide carbon dioxide buffer – High CO2 levels, take in more – Low levels, take in less • Environmental indicators • WWI wound dressing What about ecological indicators? – Antiseptic & absorbent • Peat bogs cover ~ 1% earth’s surface – Half size USA! G.Chandler Various Moss Structures Sphagnum bog (Tierra del Fuego) 10.