scholarly journals Phenotypic plasticity in the green algae Desmodesmus and Scenedesmus with special reference to the induction of defensive morphology

2003 ◽  
Vol 39 (2) ◽  
pp. 85-101 ◽  
Author(s):  
M. Lürling
1966 ◽  
Vol 44 (10) ◽  
pp. 1247-1254 ◽  
Author(s):  
J. S. Craigie ◽  
J. McLachlan ◽  
W. Majak ◽  
R. G. Ackman ◽  
C. S. Tocher

The photosynthetic fixation of14CO2was studied in 10 species of chlorophycean algae and in 9 isolates of prasinophycean algae of the genus Tetraselmis.Green seaweeds had photosynthetic rates of 2.2 to 4.4 mg CO2 × h−1 × g−1, accumulated starch, glucose, fructose, and sucrose, and excreted very little recent photosynthate.Dunaliella spp. were distinguished by a high level of organic excretion (to 29.2% of the14C fixed in 2 hours), the production of glycerol and hydrogen sulfide, and the absence of dimethyl-β-propiothetin.Tetraselmis spp. excreted relatively small amounts of photosynthate in 2 hours, and produced mannitol and dimethyl-β-propiothetin but not hydrogen sulfide.


1999 ◽  
Vol 47 (3) ◽  
pp. 361 ◽  
Author(s):  
Richard M. McCourt ◽  
Michelle T. Casanova ◽  
Kenneth G. Karol ◽  
Monique Feist

Sequences for the chloroplast-encoded large subunit of the Rubisco gene (rbcL) were used to test the monophyly of multiple isolates within species, and multiple species within genera, of green algae in the Characeae (Class Charophyceae). Parsimony and maximum likelihood analyses supported the monophyly of genera and most species, with the exception of a paraphyletic assemblage comprising isolates of two ‘species’, dioecious Chara connivens Salzm. ex A.Br. and monoecious C. globularis Thuill., which together constitute a monophyletic group. The rbcL data support the independent evolution of either monoecious or dioecious sexual systems in the two connivens-globularis, clades. Comparisons of disjunct isolates of the monotypic Lychnothamnus barbatus (Meyen) Leohn. revealed nearly identical rbcL sequences in isolates from Croatia, Germany and Australia, although all three sequences were unique. The variation exhibited by these isolates was similar to variation between isolates within species of Chara and Lamprothamnium from different continents. The limited variation may be due to dispersal of thalli or oospores between continents; however, the rarity of known intercontinental transfers of Characeae in the last two centuries suggests that the Australian population is probably not an exotic from Europe. Lychnothamnus barbatus populations in Australia and elsewhere thus merit continued protected status.


Author(s):  
L. V. Leak

Electron microscopic observations of freeze-fracture replicas of Anabaena cells obtained by the procedures described by Bullivant and Ames (J. Cell Biol., 1966) indicate that the frozen cells are fractured in many different planes. This fracturing or cleaving along various planes allows one to gain a three dimensional relation of the cellular components as a result of such a manipulation. When replicas that are obtained by the freeze-fracture method are observed in the electron microscope, cross fractures of the cell wall and membranes that comprise the photosynthetic lamellae are apparent as demonstrated in Figures 1 & 2.A large portion of the Anabaena cell is composed of undulating layers of cytoplasm that are bounded by unit membranes that comprise the photosynthetic membranes. The adjoining layers of cytoplasm are closely apposed to each other to form the photosynthetic lamellae. Occassionally the adjacent layers of cytoplasm are separated by an interspace that may vary in widths of up to several 100 mu to form intralamellar vesicles.


Author(s):  
A. E. Hotchkiss ◽  
A. T. Hotchkiss ◽  
R. P. Apkarian

Multicellular green algae may be an ancestral form of the vascular plants. These algae exhibit cell wall structure, chlorophyll pigmentation, and physiological processes similar to those of higher plants. The presence of a vascular system which provides water, minerals, and nutrients to remote tissues in higher plants was believed unnecessary for the algae. Among the green algae, the Chaetophorales are complex highly branched forms that might require some means of nutrient transport. The Chaetophorales do possess apical meristematic groups of cells that have growth orientations suggestive of stem and root positions. Branches of Chaetophora incressata were examined by the scanning electron microscope (SEM) for ultrastructural evidence of pro-vascular transport.


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