Optimization of conditions for tetraspore release and assessment of photosynthetic activities for different generation branches of Gracilaria lemaneiformis Bory

Gracilaria lemaneiformis Bory is an economically important alga that is primarily used for agar production.Although tetraspores are ideal seeds for the cultivation of G.lemaneiformis,the most popular culture method is currently based on vegetative fragments,which is labor-intensive and time-consuming.In this study,we optimized the conditions for tetraspore release and evaluated the photosynthetic activities of different colonies formed from the branches of G.lemaneiformis using a PAM(pulse-amplitude-modulated) measuring system.The results showed that variations in temperature and salinityhad significant effects on tetraspore yield.However,variations in the photon flux density(from 15 μmol m-2 s-1 to 480 μmol m-2 s-1) had no apparent effect on tetraspore yield.Moreover,the PAM-parameters Y(I),Y(Ⅱ),ETR(I),ETR(Ⅱ) and Fv/Fm of colonies formed from different branches showed the same trend:parameter values of first generation branches>second generation branches>third generation branches.These results suggest that the photosynthetic activities of different colonies of branches changed with the same trend.Furthermore,photosynthesis in G.lemaneiformis was found to be involved in vegetative reproduction and tetraspore formation.Finally,the first generation branches grew slowly,but accumulated organic compounds to form large numbers of tetraspores.Taken together,these results showed that the first generation branches are ideal materials for the release of tetraspores.

Effects of UV-B radiation on tetraspores of Chondrus ocellatus Holm(Rhodophyta),and effects of red and blue light on repair of UV-B-induced damage

We evaluated the effects of red and blue light on the repair of UV-B radiation-induced damage in tetraspores of Chondrus ocellatus Holm. Tetraspores of C. ocellatus were treated with different UV-B radiation levels(0,36,72,108,144 and 180 J/m2),and thereafter subjected to PAR,darkness,or red or blue light during a 2-h repair stage,each day for 48 days. The diameters and cellular contents of cyclobutane pyrimidine dimmers(CPDs),chlorophyll a(Chl a),phycoerythrin,and UV-B-absorbing mycosporinelike amino acids(MAAs) contents of the tetraspores were determined. Our results show that low doses of UV-B radiation(36 and 72 J/m 2) promoted the growth of C. ocellatus; however,increased UV-B radiation gradually reduced the C. ocellatus growth(greater than 72 J/m2). The MAAs(palythine and asterina-330) in C. ocellatus were detected and analyzed by LC/MS. Our results suggest that moderate red light could induce the growth of this alga in aquaculture. In addition,photorepair was inhibited by red light,so there may be some other DNA repair mechanism activated by red light. Blue light promoted the activity of DNA photolyase,greatly improving remediation efficiency. Red and blue lights were found to reduce the capacity of C. ocellatus to form MAAs. Therefore,PAR,red light,and blue light play different roles during the repair processes for damage induced by UV-B radiation.

Formation and early development of tetraspores of Polysiphonia urceolata (Rhodomelaceae,Rhodophyta)

Polysiphonia urceolata is one type of potential commercial red seaweeds used for breeding and cultivation, because of its significant biochemical and biomedical application. However, the information of breeding and seedling incubation for cultivation is limited, especially the early development. In this study, tetrasporohyte and gametophyte of P. urceolata were taken as the study materials in Huiquan Bay, Qingdao, China. The cleaned and sterilized tetrasporophytes and gametophytes were pre-cultured in sterilized seawater, then nurtured at 18℃, 25 μmol photons m^-2 s^-1 in 12：12 h （light：dark） photoperiod. Continuous observation under microscope showed that the early development consists of bipolar division stage and seedling stage. In the division stage, tetraspores germinate into bipolar sporelings that further differentiate into a colorless rhizoidal portion and a lightly pigmented upright shoot. The lightly pigmented rhizoidal cell develops to a rhizoid and the larger pigmented cell transforms to an erect axis. In the seedling stage, several quasi-protuberances appear on the erect axis and form juvenile seedlings. The results demonstrate the culture of P. urceolata from tetraspores under laboratory conditions.

Early development of Chondrus ocellatus Holm(Gigartinaceae,Rhodophyta)

Chondrus is an economically important red algae widely used for food and biochemical purpose.It early development is crucial for the culture and seedling propagation.We chose tetraspores and carpospores of Chondrus ocellatus as examples for experiment of the culture,induction and release in laboratory condition,aiming to understand early development of C.ocellatus and to apply in seedling production.Mature C.ocellatus were collected in Qingdao,China,from Nov.to Dec.2004.After the gametophyte and tetrasporophyte were brushed and washed with sterilized seawater,the algal materials were treated in 1.5%KI for 20 min,then were dried for lh to stimulate the releasing of spores.After the spores released overnight,it were cultured in PES medium,incubated at 18℃,10±2μmol/(m^(2).s^(1))in 12:12h(light:dark).The observation and recording under microscope were carried out.Continuous observation of the early development showed that both tetraspore and carpospore are similar to each other.In general,three stages of the early development were shown being division,discoid crust and seedling stages.To the division stage,the most obvious feature was the increasing of cell number;during the discoid crust stage,the discoid crust had a three-dimensional axis,and it began to differentiate into two types of cells:the basal cells and the apical cells;and to the seedling stage,several protuberances-like appeared on the discoid crusts and formed juvenile seedlings.Carpospores and tetraspores exhibited a similar development process that included division stage,discoid crust stage and seedling stage.

Microorganisms in the Zone of Submarine Volcanic Eruptions at 535-513 Ma

New anatomical features revealed in some Early Cambrian calcareous microfossils suggest comparison with Rhodophyta (red algae), which makes it possible to define their taxonomic position. A taxonomically rich Early Cambrian paleobiocoenosis has been discovered in northern Tien Shan, which exemplifies the existence on earth at 535-513 Ma (million years) of morphologically complex fungiform microorganisms and red algae in a shallow-water biotope where environmental conditions favorable for life were created as a result of submarine volcanic eruptions.

Cytochemical, Structural and Ultrastructural Characterization of Tetrasporogenesis in Bostrychia radicans (Ceramiales, Rhodophyta) from the Mangroves of Itacorubi and Rio Ratones, Santa Catarina, Brazil

Little is known about the morphology and location of macromolecules, especially proteins and carbohydrates, in vegetative and reproductive structures of mangrove species, including Bostrychia radicans. Therefore, to gain a better understanding of tetrasporogenesis in B. radicans, cytochemical, structural and ultrastructual analyses were performed. Thalli were collected from mangroves in Florianópolis, Santa Catarina, Brazil. Fertile branches were fixed and processed for light microscopy (LM), confocal microcopy and transmission electron microscopy (TEM) observations. The LM sections were stained with toluidine blue, periodic acid-Schiff and Coomassie brilliant blue. Tetrasporogenesis occurs in the pericentral cells of the terminal branches. This process is initially characterized by an increase in cell volume, resulting from the proliferation of organelles. The young tetrasporangia remain connected to the basal cell by pit connections. After a considerable increase in volume, the tetrasporocytes divide tetrahedrally, giving rise to haploid spores. During this process, there is an increasing production of starch grains, causing the organelles to group. As the organelles proliferate, the plasma membrane undergoes simultaneous invaginations toward the tetrasporangium center. The most conspicuous organelle throughout tetrasporogenesis was the Golgi complex. Polysaccharidic components are predominant in the tetrasporangium cell wall throughout tetrasporogenesis. Although protein components prevail in the cytoplasm of younger tetrasporangia, there is a predominance of reserve material with maturation. In the initial phase, there is an increase in the number of chloroplasts and a significant increment of Golgi bodies which contribute to the formation of the amorphous portion of the cell wall and possibly the biosynthesis of starch grains.