Moving onto Land Problems and Solutions
Characteristics of All Land Plants Similarities to Green Algae-Charophytes • • • • • • Chlorophyll a & b, carotenoids Starch storage in plastids Cellulosic cell walls Phragmoplast Flavonoids and phytochrome Evolution toward large immotile egg protected by sterile cells Moving onto Land Problems and Solutions • • • • Control desiccation (cuticle) Protection of gametes and embryos Transporting water and nutrients Gamete transportation – Move away from water transport; need a desiccant resistant vehicle for sperm transport Characteristics of All Land Plants Life Cycle • Sporic meiosis and Alternation of Generation • Gametophytes are haploid and produce gametes • Sporophytes are diploid, and make haploid spores in sporangia (meiosis) • Spores grow into gametophytes Phylum Bryophyta—Mosses, Liverworts, and Hornworts • Primitive land plants • Photosynthetic-free living gametophye • Zygote and sporophyte never leave female gametophyte • Sporophyte is dependant on gametophyte for nutrition • Free-swimming sperm Mosses-Life Cycle • Simple, undifferentiated leaves • No stoma nor guard cells – Exception to rule (sporophyte & hornworts) • Rely on moist environments for reproduction and plant protection • Adaptive growth form Bogs—isolated wetlands. Bogs are carbon sinks. The acidic condition of bogs is due to Sphagnum moss. Few decomposers. Why? Cold, low oxygen (anoxic), and acidic conditions. This allows organic matter (i.e., peat) to accumulate in bogs. Sphagnum Moss-Ecological and Economic Importance •Peat Products –Peatcrete –Peatwood –Insulation –Scotch –Peatmoss •Living Sphagnum moss –Sterile dressing –Absorbent material –Decoration Sphagnum moss with ballistic sporangia— Sphagnum Ballistics People of the Bog--Europe Permit studies of past cultures. Hyde Park Mastodon Moose Dung Moss-Splachnum • Splachnum only grows on moose dung. • Sporophyte mimics flowers and attracts flies on moose pies. Moss Gardening--Asia Liverworts • Thallus form of liverworts resembles human live— ”Doctrine of Signatures” • Thallus with differentiated tissues—photosynthetic layer, pores for gas exchange • Live in moist seepage areas Gemmae cup Thallus structure and asexual Reproduction (gemmae). Sexual Structures of Liverwort Gametophytes Male gametophyte with antheridiophores Female gametophyte with archegoniophores What’s next? Building a complex plant adapted to living all across land. • Mosses and liverworts are limited to moist, humid environments – – – – – – Lack vascular tissue Lack cuticle Undifferentiated leaves, stems, rhizoids Require water for reproduction Gametophyte dominated lifestyle Homospory Summary Time—Mosses and Liverworts • • • • • • gametophyte dominant lifestyle ephemeral sporophyte simple undifferentiated leaves motile sperm undifferentiated spores—homospory need moist, humid habitats for survival
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