Division Ochrophyta (Chromophyta)

Transcription

1 Division Ochrophyta (Chromophyta) I. General characteristic of the Ochrophyta II. Class Pheophyceae III. Class Bacillariophyceae Division Ochrophyta General Characteristics: na cos from ocher color chl a, c fucoxanthin major accessory pignt in Diatoms and Brown algae β-carotene major yellow pignt β-1-3-linked glucose polyr chrysolaminarin, laminarin heterokonts unique plastids Ochrophyte Chloroplasts chloroplast w/ 3 mbranes double mbrane + endoplasic reticulum layer - periplatidial endoplasmic reticulum (PER) PER contiguous with nuclear envelope thylakoids in stacks of 3 s girdle lalla Ochrophyta Characteristics cont. heterokontous flagellation one smooth shorter flagellum and one longer tinsel flagellum along with molecular data indicate monophylogeny (ssu rdna; rbcl sequence) closest relatives are Oomycetes Division Ochrophyta cont. Seven Classes: Chrysophyceae Synuorphyceae Tribophyceae Eustigmatophyceae Raphidophyceae Bacillariophyceae Pheophyceae Ochrophyta: Phaeophyceae Class Phaeophyceae (brown Algae) General features multicellular (no unicells) usual reason for its own division (Phaeophyta) thalli range from filants to psuedoparenchymatous to parenchymatous

2 cell walls are composed of cellulose fibrils in a mucopolysaccharide (alginic acid) most other features shared with other Ochrophyta (eg. heterokonts, pignts, storage products, plastid type, etc.) Heterotrichy diplohaplontic () Ochrophyta: Phaeophyceae filantous thalli Sporophyte () Gatophyte (n) Attaches to substrate often epiphytic e.g. Ectocarpus new sporophyte () Class Phaeophyceae (brown Algae) General features cont. advanced thallus forms have distinct differentiation x.s. inner dulla - non-photosynthetic outer cortex - photosynthetic ristoderm - heavy pignt growth patterns can vary diffuse Laminaria intercallary ristems transition between stipe and blade apical - end of branches Fucus Pheophyceae cont. Order Laminariales (kelps) Nereocystis complex sporophyte filantous gatophyte Lamina pneumatocyst stipe holdfast w/ haptera (blade) orders separated based on life history patterns isomorphic generations (filantous spp. Ectocarpus) Ectocarpales heteromorphic generations (Kelps) Laminariales No free living haploid stage (Fucus and other rockweeds) Fucales

3 Reproduction (asexual and sexual) Sexual reproduction plurilocular sporangia diploid - grows into new sporophyte) plurilocular gatangia - give rise to (grow on gatophytes Reproduction sexual reproduction unilocular sporangia - site of iosis give rise to n gatophyte generation n n diplohaplontic Order Ectocarpales isomorphic Pheophyceae cont. Order Laminariales (kelps) () Sporophyte () (n) e.g. Ectocarpus isogamous Gatophyte (n) Nereocystis most complex sporophyte thallus gatophyte is filantous heteromorphic reproduction is oogamous. in unilocs Sexual Reproduction Order Laminariales (kelps) cont. digitate blades Sporophyte () o. a. Wave action e.g Laminaria sp. mi Filantous gatophyte (n)

4 Order Laminariales (kelps) cont. blade - primary photosynthetic organ gas bladder - float sporophylls - specialized for reproduction N 2, O 2, CO 2, CO Order Laminariales (kelps) cont. stipe alginic acid cuticle matrix mucopolysaccharide strength/elasticity of cell wall adhesion of germinating zygote (establishnt) sieve cells (trumpet cells) in dulla flared ends transport organic materials - mannitol Order Fucales (Rock weeds) parenchymatous thallus no gatophyte (no free living haploid stage) oogamous reproduction widespread distribution Fucales recepticle concepticle oogamous no free-living haploid stage oogonia (n) antheridia (n) fusion Fucoids Cont. may be monoecious or dioecious genera separated by number of eggs in oogonia: Evolutionary Trends in Life History Patterns loss of plurilocs Fucus sp. loss of free living gatophyte Fucus sp. Ascophyllum sp. Pelvitia sp. Pelvitiopsis sp. Sargassum sp. 8 eggs 4 eggs 2 eggs 1 egg 1 egg (8 nuclei) (one fertilized) isomorphic isogamous Ectocarpus sp. Heteromorphic dominant sporophyte Laminaria sp.

5 Ochrophyta: Bacillariophyceae the Diatoms morphology: single cell non-flagellated (except in so spp.) siliceous cell wall (glass) frustule Class Bacillariophyceae cont. frustule morphology two valves upper epivalve lower hypovalve girdle band loop of silica between valves Class Bacillariophyceae cont. Taxonomy based on frustule structure Centric - radially arranged frustrules and markings Pennate - bilaterally arranged frustrule and markings raphe - line in middle of valve Class Bacillariophyceae reproduction asexual mitosis occurs and migration into valves silica deposition vesicle forms new valves form sex. reproduction regains max size new valves from hypovalve is smaller original epivalve cell is sa size so average size of population decreases Class Bacillariophyceae reproduction Sexual reproduction vegetative cell is diploid! are only haploid stage (diplonic) differs in centric and pennate diatoms

6 Class Bacillariophyceae reproduction iosis occurs to form Centric sex sperm (4 or more) and egg (1) sperm are flagellated (single n egg tinsel) and are released egg can be retained or released au zygote forms enlarged Auxospore () division of auxospore results in vegetative cells of the maximum size Class Bacillariophyceae reproduction Pennate sex vegetative cells form au au cells pair in mucilage and exchange a Zygote forms in each original cell auxospores form division results in maximum size