Transcript The Plants
THE PLANTS General Characteristics Nonvascular Plants What Are Plants? Traditionally: All the photosynthetic organisms plus Fungi Fungi have been removed to a separate kingdom Prokaryotic photosynthetic “Blue-Green Algae” removed to Bacteria (Cyanobacteria) Other “Algae” removed to the Protista Plants probably evolved from certain Charophytes “Green Algae” Characteristic Features of Plants Multicellular, with distinct tissues and organs Chlorophylls a & b; carotenoids Gametangia with outer non-reproductive cells that protect developing gametes Developing embryo enclosed in a female reproductive structure Alternation of generations Form phragmoplast and cell plate during cell division Starch is the primary food reserves in the chloroplast Cellulose is the principal component of the cell wall Sporic Meiosis Plants alternation of generations + Gamete Spores - + - + Meiosis This cell undergo meiosis 1n 2n - Gamete Fertilization Zygote Sporophyte (Diploid individual) Bryophytes: Nonvascular Plants Early land plants, require water for fertilization Two characteristics distinguish them from vascular plants a. Lack specialized vascular tissues but: Mosses have hydroids (water) and leptoids (sugar) Most Bryophytes have rhizoids (anchor) b. The nature of alternation of generation Gametophytes are nutritionally independent Sporophytes are permanently attached to gametophytes Thus the gametophyte is the noticeable and dominant generation Bryophytes: Habitats Often abundant in relatively moist habitats A number of mosses are able to survive severe temp. (also on bare rocks) Some mosses & liverworts are predominantly aquatic Bryophytes are sensitive to air pollution specially SO2 (indicators) Liverworts: Phylum Hepatophyta Thought that they cure liver diseases (Doctrine of Signature)* Less conspicuous plants Their rhizoids are single celled unlike mosses Have numerous pores (associated with air gaps) which function as stoma Gametophytes are Thallose or Leafy Liverwort Thallose Liverworts (nonleafy) The thallus is many layers thick, perennial* Mostly unisexual e.g. Marchantia Male gametophytes produce antheridia on disk headed stalks * Female gametophytes produce archegonia on umbrella headed stalks * Sexual reproduction requires water Asexual reproduction by means of Gemma cups Thallose Liverwort Return ♀ ♂ Marchantia Gemmae in a Liverwort Life cycle of Marchanta Leafy Liverworts The majority of liverworts (4000 species) are leafy Abundant in the tropics and subtropics Leaf as in mosses is one cell thick Leaves are arranged in two rows with a third of reduced leaves* Monoecious (terminal archegonium & lateral antheridium) Archegonium & the developing sporophyte are covered by perianth Leafy Liverworts By A. Nelson Nowellia curvifolia Gametophte Young sporophyte N. Curyifolia sporophyte Gametophyte Leafy Liverworts Lophocolea heterophylla Sporophyte young sporophyte Mosses: Division Bryophyta * True mosses are small inconspicuous plants Gametophytes are represented by Leaves which are one cell thick Have multicellular rhizoids, Stoma are present Have hydroids that resemble xylem tracheids Have leptoids that resemble sieve elements Sporophytes are photosynthetic Two patterns of growth: Feathery & Cushiony Mosses Atrichum undulatum “Roof Moss” Mosses morphology Sporophyte with capsule Gametophyte Feathery Mosses Feathery: Much branched, creeping Sporophytes are born laterally Feathery Mosses Cushiony mosses Atrichum undulatum Gametophytes are Bear erect and little branched a terminal sporophyte Gemmae in a Moss Gemmae •Detach from parent gametophyte and grow into new gametophyte. •An example of vegetative reproduction Tetraphis pellucida Life Cycle of a Moss Ecology of Sphagnum Leaves consist of large dead cells with pores, readily become filled with water Water holding capacity of the moss is 20 times its dry weight (5 times cotton) They form extensive peat bogs in temperate regions Peat bogs cover 1% of world's land surface (~1/2 USA) Contribute to acidity of their own habitat (pH 4) Peat is formed from accumulation of the moss and associated grasses and sedges In Ireland and other northern regions it is used as fuel