<Emphasis Type="Italic">Ulva lactuca</Emphasis>: A potential seaweed for tumor treatment and immune stimulation

This is the first report on the antitumor and immunostimulating activities ofUlva lactuca. Using the WSM (water-soluble fraction of a methanol extract fromUlva lactuca), a concentration of 140 g/mL was found to inhibit 50% of the human leukemia cell line U937 in growth, while splenocyte growth was stimulated up to a concentration of 100 μg/mL. In addition, NO production by a macrophage cell line (RAW 264.7) and alkaline phosphatase activity in mouse splenocytes were both stimulated with 10 μg/mL of WSM. Dose-dependent patterns were observed on all three cell-lines. Accordingly, the current results indicate thatUlva lactuca may be useful as a natural antitumor and immunostimulating agent.     

Effects of pH on NaCl tolerance of American elm (<Emphasis Type="Italic">Ulmus americana</Emphasis>) seedlings inoculated with <Emphasis Type="Italic">Hebeloma crustuliniforme</Emphasis> and <Emphasis Type="Italic">Laccaria bicolor</Emphasis>

In the present study, we investigated the effects of pH treatments on NaCl tolerance in mycorrhizal and non-mycorrhizal American elm. American elm (Ulmus americana) seedlings were inoculated with Hebeloma crustuliniforme, Laccaria bicolor or with both mycorrhizal fungi and subsequently subjected to different pH solutions (pH 3, 6 and 9) containing 0 mM (control) and 60 mM NaCl for 4 weeks. Inoculation with the mycorrhizal fungi did not have a large effect on seedling dry weights when the pH and NaCl treatments were considered independently. However, when the inoculated seedlings were treated with 60 mM NaCl at pH 3 or 6, shoot to root ratios and root hydraulic conductivity were higher compared with non-inoculated plants, likely reflecting changes in seedling water flow properties. At pH 6, transpiration rates were about twofold lower in non-inoculated plants treated with NaCl compared with non-treated controls. For NaCl-treated H. crustuliniforme- and L. bicolor-inoculated plants, the greatest reduction of transpiration rates was at pH 9. Treatment with 60 mM NaCl reduced leaf chlorophyll concentrations more in non-inoculated compared with inoculated plants, with the greatest, twofold, decrease occurring at pH 6. At pH 3, root Na concentrations were higher in inoculated than non-inoculated seedlings; however, there was no effect of inoculation on root Na concentrations at pH 6 and 9. Contrary to the roots, the leaves of inoculated plants had lower Na concentrations at pH 6 and 9, but not at pH 3. The results point to an interaction between ECM fungi and root zone pH for salt tolerance of American elm.     

Expression of <Emphasis Type="Italic">cspH</Emphasis> upon nutrient up-shift in <Emphasis Type="Italic">Salmonella enterica</Emphasis> serovar Typhimurium

The gene cspH , which encodes one of the cold-shock proteins in Salmonella enterica serovar Typhimurium, has previously been reported to be induced during early exponential phase at 37°C. In the present study, the expression of cspH upon nutrient up-shift at 37°C was investigated and found to be affected by DNA gyrase and DNA-binding protein Fis. When cells at stationary phase were subcultured into a rich medium, the mRNA level of cspH increased dramatically prior to the first cell division. However, when the cells were treated with DNA gyrase inhibitors, cspH mRNA was not induced upon nutrient up-shift. The low level of DNA superhelical density at the cspH promoter in part affected the expression of cspH mRNA in vitro. In addition, a fis-deficient strain had a lower level of cspH mRNA than the wild-type upon nutrient up-shift. Finally, a cspH–lacZ construct, in which the putative binding region for Fis was deleted in the cspH promoter, expressed a low level of LacZ, in contrast to the native cspH–lacZ construct.This revised version was published online in July 2004 with corrections to Fig. 4.     

The effects of nutrient addition on floral characters and pollination in two subalpine plants, <Emphasis Type="Italic">Ipomopsis aggregata</Emphasis> and <Emphasis Type="Italic">Linum lewisii</Emphasis>

The availability of soil and pollination resources are main determinants of fitness in many flowering plants, but the degree to which each is limiting and how they interact to affect plant fitness is unknown for many species. We performed resource (water and nutrients) and pollination (open and supplemental) treatments on two species of flowering plants, Ipomopsis aggregata and Linum lewisii, that differed in life-history, and we measured how resource addition affected floral characters, pollination, and reproduction (both male and female function). We separated the direct effects of resources versus indirect effects on female function via changes in pollination using a factorial experiment and path analysis. Resource addition affected I. aggregata and L. lewisii differently. Ipomopsis aggregata, a monocarp, responded to fertilization in the year of treatment application, increasing flower production, bloom duration, corolla width, nectar production, aboveground biomass, and pollen receipt relative to control plants. Fertilization also increased total seed production per plant, and hand-pollination increased seeds per fruit in I. aggregata, indicating some degree of pollen limitation of seed production. In contrast, fertilization had no effect on growth or reproductive output in the year of treatment on L. lewisii, a perennial, except that fertilization lengthened bloom duration. However, delayed effects of fertilization were seen in the year following treatment, with fertilized plants having greater aboveground biomass, seeds per fruit, and seeds per plant than control plants. In both species, there were no effects of resource addition on male function, and the direct effects of fertilization on female function were relatively stronger than the indirect effects via changes in pollination. Although we studied only two plant species, our results suggest that life-history traits may play an important role in determining the reproductive responses of plants to soil nutrient and pollen additions.     

Differential growth response of <Emphasis Type="Italic">Ulva lactuca</Emphasis> to ammonium and nitrate assimilation

Controlled cultivation of marine macroalgal biomass such as Ulva species, notably Ulva lactuca, is currently studied for production of biofuels or functional food ingredients. In a eutrophic environment, this macrophyte is exposed to varying types of nutrient supply, including different and fluctuating levels of nitrogen sources. Our understanding of the influences of this varying condition on the uptake and growth responses of U. lactuca is limited. In this present work, we examined the growth response of U. lactuca exposed to different sources of nitrogen (NH₄⁺; NO₃⁻; and the combination NH₄NO₃) by using photo-scanning technology for monitoring the growth kinetics of U. lactuca. The images revealed differential increases of the surface area of U. lactuca disks with time in response to different N-nutrient enrichments. The results showed a favorable growth response to ammonium as the nitrogen source. The NH₄Cl and NaNO₃ rich media (50 μM of N) accelerated U. lactuca growth to a maximum specific growth rate of 16.4 ± 0.18% day⁻¹ and 9.4 ± 0.72% day⁻¹, respectively. The highest biomass production rate obtained was 22.5 ± 0.24 mg DW m⁻²·day⁻¹. The presence of ammonium apparently discriminated the nitrate uptake by U. lactuca when exposed to NH₄NO₃. Apart from showing the significant differential growth response of U. lactuca to different nitrogen sources, the work exhibits the applicability of a photo-scanning approach for acquiring precise quantitative growth data for U. lactuca as exemplified by assessment of the growth response to two different N-sources.     

Antibacterial activity of<Emphasis Type="Italic">Ulva lactuca</Emphasis> against methicillin-resistant<Emphasis Type="Italic">Staphylococcus aureus</Emphasis> (MRSA)

Thein vitro antimicrobial activity of the marine green algaeUlva lactuca was examined against gram-positive bacteria, gram-negative bacteria, and a fungus. The ethyl-ether extract of algae exhibited a broad-spectrum of antibacterial activity. but not antifungal activity againstCandida albicans. In particular, theU. lactuca extract showed strong activity aganst the bacterium methicillin-resistantStaphylococcus aureus (MRSA). This result confirms the potential use of seaweed extracts as a source of antibacterial compounds or as a health-promoting food for aquaculture.     

Potential of <Emphasis Type="Italic">Eichhornia crassipes</Emphasis> for biomass refining

Here we explore the utilization of Eichhornia crassipes, commonly known as water hyacinth, as a competitive source of biomass for conversion to fuel. Ecologically, E. crassipes is the most undesirable of a class of noxious and invasive aquatic vegetation. Water hyacinth grows rapidly on the surface of waterways, forming a dense mat which depletes the surrounding environment of essential nutrients. These properties, rarely encountered in other plant systems, are features of an ideal feedstock for renewable biomass. The high characteristic water content limits the range over which the material can be transported; however it also makes E. crassipes a natural substrate for rapid microbial metabolism that can be employed as a potentially effective biological pretreatment technology. We show through a life cycle analysis that water hyacinth is a competitive feedstock with the potential to be produced at a cost of approximately 40 dollars per ton of dry mass.     

Compensatory function for water transport by adventitious roots of <Emphasis Type="Italic">Ipomoea pes-caprae</Emphasis>

To determine the role of adventitious roots in supplying water to Ipomoea pes-caprae (L.) Sweet (Convolvulaceae), we examined the effects of water deficit on water uptake and the growth patterns of leaves and shoots. After stopping the water supply from the primary root or adventitious roots, the water-uptake rate of the other root system increased steeply within 90–100 min to a level of 90% of the pretreatment water-uptake rate of the whole plant. Thus, the primary and adventitious roots can compensate for a decrease in the water-uptake rate of the whole plant caused by dehydration. The continuous growth of leaves and shoots after dehydration suggests that an increase in the water-uptake rate by either root system can support plant growth, although the growth rates of immature leaves in plants with no water supply from the primary or adventitious roots were lower than in controls. We conclude that the water supply from adventitious roots contributes to the survival and growth of plants, and will be important for vegetative propagation.     

The parameters of grain filling and yield components in common wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) and durum wheat (<Emphasis Type="Italic">Triticum turgidum</Emphasis> L. var. <Emphasis Type="Italic">durum</Emphasis>)

Final grain dry weight, a component of yield in wheat, is dependent on the duration and the rate of grain filling. The purpose of the study was to compare the grain filling patterns between common wheat, (Triticum aestivum L.), and durum wheat, (Triticum turgidum L. var. durum), and investigate relationships among grain filling parameters, yield components and the yield itself. The most important variables in differentiating among grain filling curves were final grain dry weight (W) for common wheat genotypes and grain filling rate (R) for durum wheat genotypes; however, in all cases the sets of variables important in differentiating among grain filling curves were extended to either two or all three parameters. Furthermore, in one out of three environmental conditions and for both groups of genotypes, the most important parameter in the set was grain filling duration (T). It indicates significant impact of environmental conditions on dry matter accumulation and the mutual effect of grain filling duration and its rate on the final grain dry weight. The medium early anthesis date could be associated with further grain weight and yield improvements in wheat. Grain filling of earlier genotypes occurs in more temperate environments, which provides enough time for gradual grain fill and avoids the extremes of temperature and the stress of dry conditions.     

Swift recovery of <Emphasis Type="Italic">Sphagnum</Emphasis> nutrient concentrations after excess supply

Although numerous studies have addressed the effects of increased N deposition on nutrient-poor environments such as raised bogs, few studies have dealt with to what extent, and on what time-scale, reductions in atmospheric N supply would lead to recovery of the ecosystems in question. Since a considerable part of the negative effects of elevated N deposition on raised bogs can be related to an imbalance in tissue nutrient concentrations of the dominant peat-former Sphagnum, changes in Sphagnum nutrient concentration after excess N supply may be used as an early indicator of ecosystem response. This study focuses on the N and P concentrations of Sphagnum magellanicum and Sphagnum fallax before, during and after a factorial fertilization experiment with N and P in two small peatlands subject to a background bulk deposition of 2 g N m(-2) year(-1). Three years of adding N (4.0 g N m(-2) year(-1)) increased the N concentration, and adding P (0.3 g P m(-2) year(-1)) increased the P concentration in Sphagnum relative to the control treatment at both sites. Fifteen months after the nutrient additions had ceased, N concentrations were similar to the control whereas P concentrations, although strongly reduced, were still slightly elevated. The changes in the N and P concentrations were accompanied by changes in the distribution of nutrients over the capitulum and the stem and were congruent with changes in translocation. Adding N reduced the stem P concentration, whereas adding P reduced the stem N concentration in favor of the capitulum. Sphagnum nutrient concentrations quickly respond to reductions in excess nutrient supply, indicating that a management policy aimed at reducing atmospheric nutrient input to bogs can yield results within a few years.     

A direct comparison of the performance of the seaweed biofilters, <Emphasis Type="Italic">Asparagopsis armata</Emphasis> and <Emphasis Type="Italic">Ulva rigida</Emphasis>

The tetrasporophyte of Asparagopsis armata has been previously established as a novel seaweed biofilter for integrated land-based mariculture. The species growth and biofiltration rates were much higher than the values described in the literature for Ulva spp., the most common seaweed biofilter. However, a validation of the advantage of one species over the other requires a study of the performances of these two species in the same system at the same time. In this work, we compared the biofiltration performance and biomass yield of A. armata and Ulva rigida cultivated in the effluents of a fish farm in southern Portugal. Comparisons were performed at different water renewal rates and in two seasons of the year. The maximum total ammonia nitrogen (TAN) removal rates were similar for both species in December (2.7 and 2.8 g TAN m^–2 day^–1 for U. rigida and A. armata, respectively) and higher for A. armata (6.5 g TAN m^–2 day^–1) than for U. rigida (5.1 g TAN m^–2 day^–1) in May. Higher differences were observed when estimating the nitrogen biofiltration through the organic nitrogen yield (N yield) of the biomass produced, particularly in May. This estimate is directly related with the biomass yield and the N content in the tissue which were always higher for A. armata than for U. rigida. In December, the maximum biomass yields were 71 g dry weight (DW) m^–2 day^–1 for A. armata and 44 g DW m^–2 day^–1 for U. rigida, while in May, the yield of A. armata was 125 g DW m^–2 day^–1 and of U. rigida was 73 g DW m^–2 day^–1. This study confirmed that A. armata is indeed a more efficient biofilter than U. rigida. To the best of our knowledge, the production rates reported here are the highest ever reported for macroalgae cultivated in tanks.     

Chromium uptake,retention and reduction in photosynthetic <Emphasis Type="Italic">Euglena gracilis</Emphasis>

Photosynthetic Euglena gracilis grown with different K₂CrO₄ concentrations was analyzed for its ability to take up, retain and reduce Cr(VI). For comparison, cells were also exposed to CrCl₃. Cellular Cr(VI) uptake at pH 7.2 showed a hyperbolic saturation pattern with K _m of 1.1 mM, V _m of 16 nmol (h × 10⁷ cells)⁻¹, and K _i sulfate of 0.4 mM. Kinetic parameters for sulfate uptake were similar, K _m = 0.83 mM, V _m = 15.9 nmol (h × 10⁷cells)⁻¹ and K _i chromate = 0.3 mM. The capacity to accumulate chromium depended on the ionic species, external concentration and pH of the incubation medium. Cr(VI) or Cr(III) accumulation was negligible in the acidic (pH 3.5) culture medium, in which Cr(VI) was abiotically reduced to Cr(III). At pH 7.2 Cr(VI) was fully stable and high accumulation (>170 nmol/1 × 10⁷ cells at 1 mM K₂CrO₄) was achieved; surprisingly, Cr(III) accumulation was also significant (>35 nmol/1 × 10⁷ cells at 1 mM CrCl₃). Cr(VI) was reduced by cells at pH 7.2, suggesting the presence of an external reductive activity. Cr(VI) induced an increased cysteine and glutathione content, but not in phytochelatins suggesting that chromium accumulation was mediated by monothiol compounds.     

Host physiological condition regulates parasitic plant performance: <Emphasis Type="Italic">Arceuthobium vaginatum</Emphasis> subsp. <Emphasis Type="Italic">cryptopodum</Emphasis> on <Emphasis Type="Italic">Pinus ponderosa</Emphasis>

Much research has focused on effects of plant parasites on host-plant physiology and growth, but little is known about effects of host physiological condition on parasite growth. Using the parasitic dwarf mistletoe Arceuthobium vaginatum subsp. cryptopodum (Viscaceae) and its host Pinus ponderosa, we investigated whether changes in host physiological condition influenced mistletoe shoot development in northern Arizona forests. We conducted two studies in two consecutive years and used forest thinning (i.e., competitive release) to manipulate host physiological condition. We removed dwarf mistletoe shoots in April, before the onset of the growing season, and measured the amount of regrowth in the first season after forest thinning (Study I: n=38 trees; Study II: n=35 trees). Thinning increased tree uptake of water and carbon in both studies, but had no effect on leaf N concentration or δ¹³C. Mistletoe shoot growth was greater on trees with high uptake of water and carbon in thinned stands than trees with low uptake in unthinned stands. These findings show that increased resource uptake by host trees increases resources to these heterotrophic dwarf mistletoes, and links mistletoe performance to changes in host physiological condition.     

<Emphasis Type="Italic">Arabidopsis HOG1</Emphasis> gene and its petunia homolog <Emphasis Type="Italic">PETCBP</Emphasis> act as key regulators of yield parameters

Plant hormones influence the key parameters that contribute to crop yield, including biomass, branching and seed number. We tested manipulation of cytokinin signaling as an avenue for influencing these growth parameters. Here we report a full-length cDNA coding for a cytokinin binding protein, Petunia cytokinin binding protein (PETCBP) from Petunia hybrida cv. Mitchell. PETCBP encodes for a protein that exhibits high sequence similarity to S-adenosyl-L: -homocysteine hydrolase (SAHH). Transgenic petunia plants expressing this gene in antisense orientation displayed profuse branching, delayed flowering and delayed shoot bud induction from leaf explants in vitro. Homologs were also isolated from Arabidopsis thaliana homology-dependent gene silencing 1 (HOG1) and Orzya sativa (OsCBP). Arabidopsis HOG1 showed high affinity cytokinin binding activity and modified plant architecture similar to PETCBP. Transgenic Arabidopsis plants overexpressing HOG1 showed early flowering with a significantly reduced plant biomass and number of leaves. In contrast, profuse branching, delayed flowering, increased leaf size and higher seed yield were the major phenotypes observed in the antisense suppression lines. These results suggest that genetic manipulation of this cytokinin binding protein or its orthologs could be used for improving crop biomass and seed yield.     

Arbuscular mycorrhizal fungi colonize decomposing leaves of<Emphasis Type="Italic"> Myrica parvifolia</Emphasis>,<Emphasis Type="Italic"> M. pubescens</Emphasis> and<Emphasis Type="Italic"> Paepalanthus</Emphasis> sp.

Hyphae and vesicles of arbuscular mycorrhizal fungi (AMF) were found within the decomposing leaves of Myrica parvifolia, M. pubescens and Paepalanthus sp. at three montane sites in Colombia. Hyphae, vesicles, and arbuscule-like structures were also found within scale-like leaves of the rhizomes of Paepalanthus sp. The litter found in the vicinity of the roots was divided into three decomposition layers. The highest AMF colonization occurred in the most decomposed leaves, which were in close association with roots. In contrast, there were no differences in AMF colonization of roots present in the different decomposition layers. Colonization of decomposing leaves by AMF did not differ between the two closely related species M. parvifolia and M. pubescens, nor between two sites (Guatavita and Zipacón, Colombia) differing in soil fertility. Occurrence of vesicles in decomposing leaves was correlated with abundant AMF extraradical hyphae among the leaves. We propose that AMF enter decomposing leaves mechanically through vascular tissue. As a consequence, AMF are well positioned to obtain and efficiently recycle mineral nutrients released by decomposer microorganisms before their loss by leaching or immobilization in soil.     

The Asian red seaweed <Emphasis Type="Italic">Grateloupia turuturu</Emphasis> (Rhodophyta) invades the Gulf of Maine

We report the invasion of the Gulf of Maine, in the northwest Atlantic Ocean, by the largest red seaweed in the world, the Asian Grateloupia turuturu. First detected in 1994 in Narragansett Bay, Rhode Island, south of Cape Cod, this alga had expanded its range in the following years only over to Long Island and into Long Island Sound. In July 2007 we found Grateloupia in the Cape Cod Canal and as far north (east) as Boston, Massachusetts, establishing its presence in the Gulf of Maine. Grateloupia can be invasive and may be capable of disrupting low intertidal and shallow subtidal seaweeds. The plant's broad physiological tolerances suggest that it will be able to expand possibly as far north as the Bay of Fundy. We predict its continued spread in North America and around the world, noting that its arrival in the major international port of Boston may now launch G. turuturu on to new global shipping corridors.     

<Emphasis Type="Italic">Nepenthes</Emphasis> group <Emphasis Type="Italic">Montanae</Emphasis> (Nepenthaceae) in Indo-China,with <Emphasis Type="Italic">N. thai</Emphasis> and <Emphasis Type="Italic">N. bokor</Emphasis> described as new

Summary  A key is presented to the Nepenthes group Montanae in Peninsular Malaysia, Thailand and Cambodia. Nepenthes bokor Cheek is described from Cambodia and Nepenthes thai Cheek from peninsular Thailand. The affinities of both taxa are discussed and their conservation status assessed.