BIOL 2P93 Lecture Notes - Lecture 6: Cytokinesis, Bryophyte, Cytoskeleton
22 Jan 2016
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Represented in many forms like spirogyra, common branched filamentous charophyte. Desmids related to spirogyra but lack flagellated cells. Most desmid cells have two sections connected by a narrow constriction (isthmus) like xanthidium armatum. Coleochaete can branch filamentous/discoid +has uninucleate veg cells, each w/ one large chloroplast embedded pyrenoid. Sexual reproduction is oogamous: non-motile large gamete (egg) + smaller motile gamete (sperm). Zygotes attached to parental thallus + start growth of protective layer by parent cells = have wall ingrowth-like structures similar to gametophyte- sporophyte junction of bryophytes = transfer cells (nutrient transport btwn gametophyte + sporophyte). Order charales 81-400 species found in freshwater + brackish water. like. Charales thallus differentiated into nodal + internodal regions, tissue organization in nodal regions resembles parenchyma tissue of higher plants. Charales lc not well understood: sperm made in multicellular antheridia (sperm-producing structure), eggs borne in oogonia (unicellular female sex organs) enclosed by long + twisted cells.
