Influence of plant growth regulators, polyamines and glycerol interaction on growth and morphogenesis of carposporelings of Grateloupia cultured in vitro

The influence of the plant growth regulators 2,4-D, GA₃, BA and kinetin, and the polyamines putrescine, spermidine and spermine were tested on axenic in vitro cultures of carposporelings of Grateloupia doryphora. The auxin 2,4-D (10^-3 M) and the polyamine spermine (10^-6 M and 10^-3 M) induced a callus (disorganised cell mass that arose from the organised tissue of the carposporeling, as demonstrated by microscopic monitoring of the tissue). Putrescine and spermidine (10^-3 M) transformed the carposporelings into cell masses that produced shoots. BA (10^-3 M) and kinetin (10^-6 M and 10^-3 M) were inhibitory. In 10^-1 M glycerol-containing culture medium, which is known to induce the formation of morphogenic cell masses, the addition of GA₃ M) resulted in the inhibition of the morphogenesis (i.e. shoot emission) in the cell mass. The kinetin at 10^-6 M inhibited morphogenesis, whilst at 10^-3 M inhibited even the formation of the cell masses. The combination of glycerol (10^-1 M) and the auxin 2,4-D (10^-6 and 10^-3 M) or the polyamines putrescine, spermidine and spermine (10^-6 and 10^-3 M) resulted in a bigger size of the cell masses that led to a higher amount of shoots per cell mass than in glycerol alone. This revised version was published online in June 2006 with corrections to the Cover Date.     

磷限制下大型海藻与微藻间资源竞争理论的实验验证

用一次性培养法结合Monod方程测得海洋微藻-亚心型扁藻(Tetraselmis subcordiformis (Wile) Hazen)与大型海藻-孔石莼(Ulva pertusa Kjellm.)磷限制下的生长动力参数.孔石莼具有较低的半饱和生长常数及最大生长率,其分别为0.016 μmol/L和0.16 d-1,而亚心型扁藻的半饱和生长常数和最大生长率分别是0.021 μmol/L 和0.83 d-1. 两种藻类间的营养竞争实验采用半连续培养法在磷限制条件下进行,实验过程中,分别对两者施予相同或不同的去除率,使两者享有相同或不同的资源需求值R*.由Monod方程所作的竞争预测与实验观察结果的比较显示:仅在两种藻类间的资源需求值R*差异显著(t检验,P＜0.01)时,Monod方程才能对竞争结果作出较为准确的预测;在两种藻类享有相同的资源需求值R*时,亚心型扁藻在竞争中取代孔石莼.Monod模型仅能部分预测大型海藻与海洋微藻间的竞争结果.     

Stabilisation of ‘Green tides’ Ulva by a method of composting with a view to pollution limitation

85 000 m³ of Ulva sp. is harvested each year in Brittany (France) during a 3–4-month season. Spreading is often impossible and the alga does not keep for more than a few days. Storage results in objectionable odours and release of a liquified fraction. Such pollution can be suppressed by composting the alga with the lowest possible quantity of ligno-cellulosic substrates. This results in the stabilisation of the seaweed, and its use can thereby be delayed. This system of processing the seaweed decreases the cost of treatment by composting and the product can be used either as a substrate for later composting or as an organic enhancing and fertilising agent. (*author for correspondence)     

Composition,uniqueness and variability of the epiphytic bacterial community of the green alga Ulva australis

Green Ulvacean marine macroalgae are distributed worldwide in coastal tidal and subtidal ecosystems. As for many living surfaces in the marine environment, little is known concerning the epiphytic bacterial biofilm communities that inhabit algal surfaces. This study reports on the largest published libraries of near full-length 16S rRNA genes from a marine algal surface (5293 sequences from six samples) allowing for an in-depth assessment of the diversity and phylogenetic profile of the bacterial community on a green Ulvacean alga. Large 16S rRNA gene libraries of surrounding seawater were also used to determine the uniqueness of this bacterial community. The surface of Ulva australis is dominated by sequences of Alphaproteobacteria and the Bacteroidetes, especially within the Rhodobacteriaceae, Sphingomonadaceae, Flavobacteriaceae and Sapropiraceae families. Seawater libraries were also dominated by Alphaproteobacteria and Bacteroidetes sequences, but were shown to be clearly distinct from U. australis libraries through the clustering of sequences into operational taxonomic units and Bray–Curtis similarity analysis. Almost no similarity was observed between these two environments at the species level, and only minor similarity was observed at levels of sequence clustering representing clades of bacteria within family and genus taxonomic groups. Variability between libraries of U. australis was relatively high, and a consistent sub-population of bacterial species was not detected. The competitive lottery model, originally derived to explain diversity in coral reef fishes, may explain the pattern of colonization of this algal surface.     

The polyamine spermine induces cystocarp development in the seaweed <Emphasis Type="Italic">Grateloupia</Emphasis> (Rhodophyta)

Polyamines such as putrescine, spermidine and spermine are ubiquitous aliphatic amines involved in reproductive events in plants and algae, and first become evident through changes in endogenous levels during reproductive development. To examine whether the differences observed in polyamines, during carposporogenesis, in the red alga Grateloupia, followed a specific pattern as is seen in other organisms, infertile axes (i.e. not showing cystocarps) were excised from the same holdfast of female fertilized individuals (i.e. showing cystocarps in other axes), and cultivated until the cystocarps became visible. Changes in the endogenous levels of free putrescine, spermidine and spermine were monitored over the 8 days of culture. The activity of enzymes related to polyamine metabolism, such as l-ornithine decarboxylase (ODC), diamine oxidase and polyamine oxidase, was measured at the beginning and end of the experimental period. Up to 50% of the infertile axes became fertile and produced cystocarps at a density of 1.91 ± 0.1 cystocarps mm⁻² after 8 days. The endogenous content of spermine increased markedly over the first 5 days of culture, then decreased to the initial level by day 8. Spermidine followed a similar pattern to spermine, whereas putrescine remained at high levels, until day 5 when it decreased abruptly. The activity of ODC was less on day 8 than on day 0, whereas the activities of diamine oxidase and polyamine oxidase increased. In parallel experiments with explants from infertile axes, exogenously added spermine (10⁻⁶ M) increased the number of cystocarps, and reversed the effect of cyclohexylamine (CHA), which is known to inhibit polyamine synthesis in Grateloupia. Serial sectioning and microscopic observation of specimens from explants cultivated in 10⁻⁶ M spermine indicated that cystocarp development was induced. The results suggest that, during transition from infertile to fertile spermine is accumulated, thus favouring the development of cystocarps, given the presumed role of spermine as an inducing agent.     

Suspension culture of gametophytes of transgenic kelp in a photobioreactor

Transgenic Laminaria japonica gametophytes producing a recombinant tissue-type plasminogen activator (rtPA) protein, which is an effective third-generation thrombolytic agent for acute myocardial infarction (AMI), were cultured in an illuminated bubble column bioreactor. A maximum final dry cell weight of 1120 mg l⁻¹ was obtained in batch culture with an initial dry cell weight of 126 mg l⁻¹ and with aeration rate of 1.2 l air min⁻¹ l⁻¹ culture, nitrate at 1.5 mM and phosphate at 0.17 mM. The yield of rtPA was 56 μg g⁻¹ dry cell wt. This is the first report regarding cultivation of a transgenic macroalga in a bioreactor.Revisions requested 27 January 2005 and 14 April 2005; Revisions received 6 April 2005 and 17 May 2005     

ONTOGENETIC CHANGES IN BUOYANCY,BREAKING STRENGTH,EXTENSIBILITY, AND REPRODUCTIVE INVESTMENT IN A DRIFTING MACROALGA TURBINARIA ORNATA (PHAEOPHYTA)1

Turbinaria ornata (Turner) J. Agardh is a tropical alga that disperses by detached, reproductively mature floating fronds. Material properties (breaking stress, breaking extension), buoyancy, and the proportion of reproductive tissue per frond were measured for juvenile, adult, and old fronds of T. ornata. Correlations between these factors indicate that as fronds age and become more reproductively mature, the tissue in their stipes (where they break) becomes weaker, more brittle, and the overall buoyancy of the frond increases. Measurement of drag force experienced by fronds from each ontogenetic stage allowed calculation of the environmental stress factor (ESF), which indicates the likelihood of detachment of a frond in the flow environment of its habitat. The ESF for fronds of each ontogenetic stage predicted that reproductively mature fronds (adult and old) break more readily than immature (juvenile) fronds. Increased proportions of reproductively mature fronds in floating rafts following storms compared with the proportion of mature fronds attached to the substratum support the ESF predictions. This combination of ontogenetic changes in material properties, buoyancy, and reproductive maturity in combination with the life history of T. ornata may contribute to the dispersal of this alga throughout French Polynesia.     

磷限制下大型海藻与微藻间资源竞争理论的实验验证(英文)

用一次性培养法结合Monod方程测得海洋微藻_亚心型扁藻 (Tetraselmissubcordiformis (Wile)Hazen)与大型海藻_孔石莼 (UlvapertusaKjellm .)磷限制下的生长动力参数。孔石莼具有较低的半饱和生长常数及最大生长率 ,其分别为 0 .0 16 μmol/L和 0 .16d-1,而亚心型扁藻的半饱和生长常数和最大生长率分别是 0 .0 2 1μmol/L和 0 .83d-1。两种藻类间的营养竞争实验采用半连续培养法在磷限制条件下进行 ,实验过程中 ,分别对两者施予相同或不同的去除率 ,使两者享有相同或不同的资源需求值R 。由Monod方程所作的竞争预测与实验观察结果的比较显示 :仅在两种藻类间的资源需求值R 差异显著 (t检验 ,P <0 .0 1)时 ,Monod方程才能对竞争结果作出较为准确的预测 ;在两种藻类享有相同的资源需求值R 时 ,亚心型扁藻在竞争中取代孔石莼。Monod模型仅能部分预测大型海藻与海洋微藻间的竞争结果。     

Some observations on polarity and regeneration in Enteromorpha

The regeneration of two types of Enteromorpha has been investigated. Small tubular sections cut from the thallus develop rhizoids along the basal cut edge and papillae from the apical cut edge. The capacity for regeneration is greatest in segments from the middle and base of the thallus and least in apical sections. Regeneration in various liquid culture media at different light intensities and temperatures and on solid agar media has been tested. The addition of growth substances and extracts from Enteromorpha thalli always stimulate regeneration but in no way alter the polarity. The results are compared with previous conflicting accounts of regeneration of Enteromorpha.