Seasonal changes in the chemical and gelling characteristics of agar from Gracilaria verrucosa collected in Turkey

The chemical and gelling properties of agar from G. verrucosa collected from Izmit bay in Turkey at different months of the year were studied. Purification of agar was performed by using amylase treatment and isopropyl alcohol precipitation. The phycocolloid content was between 24.0–43.0% of the algal dry weight and was maximum in summer collected algae. Relative total sulfate and 3,6-anhydrogalactose content in the agar were determined from the ratios of infrared spectroscopy band intensities at 1250/2920 cm^–1 and 930/2920 cm^–1, respectively. 3,6-anhydrogalactose and sulfate contents were the highest in agar from algae collected from June until November and January until July, respectively. The gel strength of native agar were the highest from in autumn collected algae and increased to about 1250 N m^–2 after alkali treatment. Thus, this study demonstrated that G. verrucosa from Turkey produces an agar with optimal chemical and gelling properties after alkali-treatment in fall and winter collected algae and may be used for industrial agar production.     

Viability and dissemination of spermatia of Gracilaria verrucosa (Gracilariales,Rhodophyta)

The dissemination and viability of Gracilaria verrucosa spermatia were tested. Crosses were performed among three males and three females from Cape Gris Nez, northern France. Laboratory experiments show that spermatia have a mean fertile life of about five hours. Field studies show that spermatia are dispersed by stream and tidal currents and that fertilization can occur at least 80 m from a population.     

Determination of the composition of the fibrillar part of Gracilaria verrucosa (Gracilariales,Rhodophyta) cell wall in order to prepare protoplasts

The cell wall of Gracilaria verrucosa is composed of two fractions: a matrix made of agar and a skeleton whose composition is unknown. This fibrillar part was isolated using both physical and chemical techniques. Total hydrolysis followed by gas-liquid chromatography allowed us to establish the sugar composition. Enzymatic degradations were carried out with cellulases, xylanases, agarases and pectinases. Efficiencies of the enzymatic digestions were monitored by both chemical analysis and electron microscopy. Pectinases had no effect. The fibrillar part was composed mainly of a cellulosic network that was unmasked by the xylanase action and degraded after cellulase digestion. The results suggest that a cocktail composed of agarases and cellulases can be used successfully to prepare protoplasts from Gracilaria verrucosa.     

Nuclear-encoded protein-coding genes of the agarophyte Gracilaria verrucosa (Gracilariales,Rhodophyta)

Single-copy nuclear genes encoding cytosolic glyceraldehyde-3-phosphate dehydrogenase (GapC), triosephosphate isomerase (TPI1) and polyubiquitin (UBI6R), plastid-localized GAPDH (GapA), and mitochondrial aconitase (m-ACN), together with their corresponding cDNAs, have been cloned or PCR-amplified from Gracilaria verrucosa, sequenced, and characterized by genomic Southern hybridization. Three spliceosomal introns were found, one each near the 5 end of GapA, GapC, and m-ACN. Codon usage is biased, with third-position A's underrepresented. Nucleotide compositions of the genes are balanced except in TPI1. Upstream promoter structure, downstream poly(A) processing signals, intron splice junctions, and one translation initiation site were analyzed. Poly(A) processing features of these red algal genes resemble those of green plants more than those of animals.     

An Inositol-Containing Sphingolipid from the Red Alga Gracilaria verrucosa

An unusual polar lipid was isolated from the red alga Gracilaria verrucosa. Inositol, sphingosine bases, fatty acids, and phosphate were identified by GC and GC-MS analysis among the products of its acid methanolysis. On the basis of the lipid composition, chromatographic behavior, chemical properties, and mass spectra, the inositol phosphoceramide structure was proposed for this lipid. Similar lipids were previously found only in fungi and some protozoa.     

Effects of temperature and salinity on the growth of Gracilaria verrucosa and G. chorda, with the Potential for mariculture in Korea

Effects of temperature and salinity on the growth of the two agarophytes, Gracilaria verrucosa (Hudson) Papenfuss and Gracilaria chorda Holmes were examined in Korea. Both species grew over a wide range of temperatures (10–30 ^∘C) and salinities (5–35‰), and grew well at 17–30 ^∘C and a salinity of 15–30‰. In culture, G. verrucosa grew faster than G. chorda and their maximum growth rates were 4.95% day⁻¹ (30 ^∘C, 25‰) and 4.47% day⁻¹ (at 25 ^∘C, 25‰), respectively. In the field population the maximum growth and fertility of G. chorda were observed in summer. The growth rate of G. verrucosa was slightly higher than that of G. chorda for 2 weeks on the cultivation rope and in culture but it was much lower after being contaminated with epiphytes. The biomass of the epiphytes was 0.82 g dry wt. per host plant in G. verrucosa and 0.001 g in G. chorda. G. chorda exhibited resistance to epiphytism and grew 7 times in length and the dry weight increased 15 times after 55 days. In conclusion, G. chorda appears to be a good agarophyte with a fast growth rate and resistance to epiphytesm, and compared with G. verrucosa, has good potential for commercial cultivation.     

Isolation and characterisation of a fourth hemagglutinin from the red alga, Gracilaria verrucosa, from Japan

Isolation and characterisation of marine algal hemagglutinins or lectins are essential for their potential industrial application as specific carbohydrate affinity ligands. The phosphate buffer extract of the red alga, Gracilaria verrucosa (Huds.) Papenfuss (Gigartinales, Rhodophyta) from Japan is known to contain three different hemagglutinins. The extract of the alga collected in March 1993 from Kagawa Prefecture, Japan, was purified by ammonium sulphate fractionation, ion exchange and gel filtration chromatography. Using gel filtration, two peaks were obtained (hereafter Peak 1 and Peak 2) which differed in molecular size and hemagglutinating activity against horse erythrocytes. Peak 1 corresponded to the known high molecular weight hemagglutinin, H-GVH. Peak 2 contained large amounts of hexose and sulphate along with a small amount of protein. It had a low molecular weight (gel filtration) similar to that of two of the previously reported G.verrucosa hemagglutinins but differed in its electrophoretic behaviour. Peak 2 is therefore a fourth hemagglutinin. Its activity was not inhibited by any of the monosaccharides tested but by the complex glycoproteins such as asialofetuin and fetuin. It had no divalent cation requirement for hemagglutination. The properties of this novel hemagglutinin could prove useful in industrial applications. This revised version was published online in June 2006 with corrections to the Cover Date.     

Seasonal variation in agar composition and properties from Gracilaria gracilis (Gracilariales,Rhodophyta) of the Patagonian coast of Argentina

Seasonal variation of agar from specimens of a commercially exploited population of Gracilaria gracilis (Stackhouse) Steentoft, Irvine & Farnham in the Patagonian coast of Argentina was studied. For each seasonal harvest, random samples of plants were pooled for subsequent polysaccharide extraction at different water temperatures and agar physico‐chemical properties and composition were determined. Both spring and summer plants yielded 30% and 41% of agar, respectively, which differed slightly in their at rest rheological behavior. Spring and summer plants produced strong gels (238 and 218 g cm^?2, respectively), but the latter gels had nil adhesiveness. In autumn plants, agar yield decayed to 19%, though the product still maintained similar gel strength (210 g cm^?2). Adhesiveness in this product was at least an order of magnitude higher than in the others, concomitant with a peak in the formation of tetraspores and carpospores. This suggests a biological role for the galactan in the initial attachment of spores to the substrate. But since fall corresponds to the settling of reproductive structures, caution should be taken to harvest the algae once spores have been shed from mother plants.     

Use of the green alga Ulva rigida C. Agardh as an indicator species to reassess metal pollution in the Thermaikos Gulf, Greece, after 13 years

The concentrations of metals (Mn, Pb, Fe, Zn, Cu, Cd,Co, Ni, Cr, Na, K, Ca, Mg) were determined in thegreen alga Ulva rigida, in the sediment andseawater of Thermaikos Gulf (Greece) during monthlysamplings in 1994–1995. This Gulf is the recipientof domestic and industrial effluents. Pb, Fe, Cu, Coand Cr concentrations in U. rigida at the studyarea were higher than those 13 years earlier andapparently came from different sources than those forZn, Cd and Ni. The relative abundance of metals inthe alga decreased in the order: Mg > Na > K >Ca > Pb > Fe > Mn > Zn > Cr, Cu > Ni >Co > Cd. Only Cu concentrations in the alga fromKalochori and Cd ones from Viamyl showed significantseasonal changes. Cu and Cd concentrations ingeneral followed the same pattern of variation, withminimum values in winter-spring. This pattern isdiscussed in relation to growth dynamics and tissueage. Only Pb concentrations in the alga showed asignificant positive correlation with concentrationsin the seawater. There were both positive andnegative correlations among some metals in the alga. It is concluded that U. rigida can be used as anindicator species, especially for Pb.     

Differences in response between haploid and diploid isomorphic phases of Gracilaria verrucosa (Rhodophyta: Gigartinales) exposed to artificial environmental conditions

This study tests the responses of juvenile gametophytes and tetrasporophytes (holdfast stage) of the isomorphic alga Gracilaria verrucosa under different environmental conditions.Estimations of survival and growth of holdfasts of haploid and diploid juvenile individuals were performed in natural sea-water and artificial culture medium, and under stringent conditions using lead as a toxin and ultra violet radiation as a mutagen. Results indicate that (i) holdfasts of haploid juveniles grow better than diploids in non-optimal medium conditions; (ii) holdfasts of diploid juveniles have a better tolerance to lead than haploids; and (iii) slight advantage of holdfasts of diploid juveniles grow better than haploids under U.V. radiation.     

真江蓠(Gracilaria verrucosa)对网箱养殖海区的生态修复及生态养殖匹配模式

2006年8～9月,在浙江象山港花鲈(Lateolabrax japonicus)养殖网箱中吊养真江蓠(Gracilaria verrucosa)对网箱养殖造成的水体富营养化进行生态修复研究.通过45d内的平面监测、定点跟踪监测和断面监测,结果表明:该网箱养殖区水体呈严重富营养化状态,营养状态指数(E)为32.00,其营养盐分布由高浓度的中心区向周围150m非养殖水域扩散;真江蓠对养殖区的富营养化海水具有较好的修复效果:江蓠生态修复区及其相邻网箱中水体PO4-P、NO2-N、NH4-N和NO3-N含量显著低于非修复区(P＜0.01),修复区海水PO4-P、NO2-N、NH4-N和NO3-N浓度比非修复区分别降低22%～58%、24%～48%、22%～61%和24%～47%.养殖真江蓠45d后,修复区水体DO浓度和透明度显著高于非修复区(P＜0.05),DO平均提高28%,透明度平均提高30%;而修复区水体Chl-a浓度显著低于非修复区(P＜0.05),平均降低49%.通过建立基于N平衡的鱼藻生态养殖模式,每收获1kg花鲈至少需要匹配江蓠4.7 kg wet wt才可实现对鱼类排放N的完全吸收.因此网箱内栽培江蓠的混合生态养殖模式,可平衡因经济动物养殖所带来的额外营养负荷,有利于实现动物养殖环境的自我修复.     

Callose deposition and breakdown, followed by phytomelan synthesis in the seed coat ofGasteria verrucosa (Mill.) H. Duval

Summary In the seed coat ofGasteria verrucosa the deposition of phytomelan takes place during seed development in three stages. Phytomelan is a black cell wall material which is chemically very inert. First the radial walls and part of the transverse cell wall of the outer epidermis of the outer integument become thickened by exocytosis of dictyosome vesicles. Callose is deposited at the tangential plasma membrane against those walls. After the callose deposition about two thirds of the original cell volume is filled with callose. During the second stage the callose is broken down, probably into glucose monomers or small polymers. At the same time cellulose is deposited at the outer tangential plasma membrane, forming a wall between the dissolving callose and the plasma membrane. In the third phase small granules appear in the solution of dissolved callose. which grow out and finally fuse to form a block of phytomelan, consisting of spherical 15-nm units. Remarkable is the function of the callose: it determines the size of the phytomelan block, and it probably functions as carbohydrate source for the phytomelan synthesis and/or for the cellulose inner layer. In this study transmission electron microscopy and cryo scanning electron microscopy are used to study the three developmental stages of the formation of the phytomelan layer.     

Seasonal variation of metal accumulation and translocation in yellow pond-lily (Nuphar lutea)

Abstract

Heavy metal bioaccumulation and translocation properties of aquatic plants are interesting because of their potential use in phytoextraction. However, there is not enough knowledge about the seasonal changes of the metal distribution properties of aquatic plants. Our study focused on seasonal variation of some heavy metals in relation to their bioaccumulation and translocation in Nuphar lutea, a floating leaved, widespread plant that is important to wildlife. In this study, N. lutea, corresponding sediment and water samples were collected at different seasons from Lake Abant (Turkey) and analysed for their heavy metal content (Pb, Cr, Cu, Mn, Ni, Zn and Cd). Accumulation and translocation of heavy metal ratios were calculated seasonally. It was found that Cr and Zn were actively transported from sediment to the root, where they accumulated especially in summer; it was also shown that Cu, Mn and Zn were not only taken up from the sediment but also from the surrounding water. The investigations suggested that translocation ratios for leaf/root of Pb, Cr, Mn and Zn reached their highest levels in spring. It was found that the bioaccumulation and translocation of heavy metals at different parts of N. lutea changes with respect to season and the type of heavy metal.