Green Algae and Slime Mold - Botany - Lecture Slides, Slides of Botany and Agronomy

Download Green Algae and Slime Mold - Botany - Lecture Slides and more Slides Botany and Agronomy in PDF only on Docsity! Green Algae and Slime Mold Green algea: Phylum Chlorophyta • Most aquatic (freshwater and marine) • Also found on snow, tree trunks, soil, lichens, sponges • Ecologically important • 350 genera, 17,000 species • Resemble plants Docsity.com • They come in a wide variety of shapes and forms, • including free- swimming unicellular species, colonies, non-flagellate unicells, filaments, and more. Docsity.com Class Ulvophyceae • Primarily marine some freshwater • Filamentous of flat sheet of cells • Cladophora Docsity.com Ulva- sea lettuce Docsity.com Class Charophyceae • Resemble Bryophytes and Vascular plants • Spirogyra – Ribbon like chloroplast – No flagellated cells – Unbranched filamentous – Conjugation repro. – Frothy or slimy floating masses in freshwater Docsity.com There are 3 groups of Bryophytes;- Liverworts Leafy liverworts (4,000-6,000 species) - predominately tropical and poorly covered in most texts Thallose liverworts (~3,500 species) - these are further sub-divided into simple and complex thalloids Hornworts Mosses (~10,000 species) • These are generally viewed as three monophyletic lineages emerging from the very earliest land plants. Docsity.com Liverworts (Hepaticophyta) About 6000 species • Two growth forms - thallose and leafy • Liverwort leaf cells each containing two to five (grey) oil bodies (as well as numerous chloroplasts). • Absorb water and nutrients through entire surface • Form single celled rhizoids for attachment • Lack stomata, but contain air pores that remain open • "Basal" group of plants, probably most like plant ancestors Docsity.com Marchantia - • common thallose liverwort, reproduces asexually by formation of gemmae • Sporophyte usually small and short-lived • Spore dispersal facilitated by elaters (hygroscopic cells) Docsity.com Hornworts: Phylum anthocerophyta Small taxon (less than 100 species) • Tall, narrow sporophytes with indeterminate growth • Intercalary (basal) meristem in sporophyte • Form symbiotic associations with cyanobacteria • Single chloroplast per cell (important taxonomic character) • Spores have pseudoelaters • Have well-defined stomata Docsity.com Mosses (Bryophyta) Large group of plants - about 14,000 species • All are “leafy”, often with midvein • Produce multicellular rhizoids • Many produce stomata on sporophytes • Typically dioecious (separate male and female gametophytes) • Unbranched sporophyte with single terminal sporangium known as a capsule borne on an elongated stalk called a seta • The calyptra (gametophytic tissue) comes off and the capsule lid, the operculum, bursts off. A ring of teeth, the peristome, is hygroscopic and aids in spore dispersal. Each capsule may contain up to 50 million spores. • Spores germinate to form a filamentous protonema • Many mosses have primitive conducting cells: Hydroids - water conducting cells Leptoids - sap conducting cells It is unclear wheter hydroids and leptoids are homologous or analogous to the xylem and phloem of vascular plants Docsity.com Mosses and leafy liverworts can be confused. • Leaves of leafy liverworts never have a mid-rib (unlike those of most mosses). • Mosses have multicellular rhizoids vs. the unicellular rhizoids of liverworts • The capsules are quite different, as we will see • Moss leaves are of equal size and spirally arranged while the main leaves of liverworts are arranged in one plane on either side of the stem with a third row of smaller leaves on the underside of the stem. • Moss leaves are never lobed • Oil bodies occur in the leaves of 90% of liverworts, but are absent from moss leaves. Docsity.com • Like the rest of land Plants, bryophytes produce an embryo- embryophytes • Evolved from green algae ancestors • Related to charophytes • Group of simple land plants • Moist habitat Docsity.com Like other land plants, the Bryophytes:- • have multicellular sex organs, i.e. the gametes are enclosed by a sterile jacket of cells • are parenchymatous, not filamentous • retain the zygote within the female sex organ and allow it to develop into an embryo there • have cutin (a cuticle) on the plant and spores Docsity.com Bryophytes, in contrast, • have no lignin usually • are small, low-lying, (generally) moisture- loving plants • have no roots, only filamentous rhizoids Docsity.com • As with the liverworts the plant that we commonly see is the gametophyte. It shows the beginnings of differentiation of stem and leaves - but no root like structures (rhizoids). • Mosses may have rhizoids and these may be multicellular but they do little more than hold the plant down. Docsity.com Ecology of mosses • Mosses require abundant water for growth and reproduction. • tolerate dry spells • occupy 1% of the earth's surface (half the area of the USA). Docsity.com