Competition between Salvinia minima and Spirodela polyrhiza mediated by nutrient levels and herbivory

We investigated the effects of initial biomass, nutrients, herbivory, and competition with Spirodela polyrhiza (L.) Schleid on Salvinia minima Baker biomass and density. S. minima populations were subjected to two levels of herbivory (control vs. two adults per plant) from the weevil Cyrtobagous salviniae Calder and Sands and eight levels of competition from S. polyrhiza, while growing in high (5 mg N l⁻¹) or low (0.5 mg N l⁻¹) nutrient conditions. Herbivory was the most important factor in S. minima biomass production while competition or fertility had no measurable impact. In contrast, S. polyrhiza biomass was mediated primarily by nutrients, not competition. There was no herbivory treatment for this plant. S. polyrhiza was superior to S. minima at converting nutrients to biomass but this did not give it a competitive advantage since S. minima biomass was unchanged when herbivory was absent. S. minima can generally overtop S. polyrhiza which, in turn, can form multiple layers within its mat. These characteristics may act to lessen competition between these species, thereby permitting their habitat sharing.     

Treatment of industrial wastewater with two-stage constructed wetlands planted with Typha latifolia and Phragmites australis

Industrial wastewater treatment comprises several processes to fulfill the discharge permits or to enable the reuse of wastewater. For tannery wastewater, constructed wetlands (CWs) may be an interesting treatment option. Two-stage series of horizontal subsurface flow CWs with Phragmites australis (UP series) and Typha latifolia (UT series) provided high removal of organics from tannery wastewater, up to 88% of biochemical oxygen demand (BOD₅) (from an inlet of 420 to 1000 mg L⁻¹) and 92% of chemical oxygen demand (COD) (from an inlet of 808 to 2449 mg L⁻¹), and of other contaminants, such as nitrogen, operating at hydraulic retention times of 2, 5 and 7 days. No significant (P < 0.05) differences in performance were found between both the series. Overall mass removals of up to 1294 kg COD ha⁻¹ d⁻¹ and 529 kg BOD₅ ha⁻¹ d⁻¹ were achieved for a loading ranging from 242 to 1925 kg COD ha⁻¹ d⁻¹ and from 126 to 900 kg BOD₅ ha⁻¹ d⁻¹. Plants were resilient to the conditions imposed, however P. australis exceeded T. latifolia in terms of propagation.     

Competitive effects of Phragmites australis on the endangered artesian spring endemic Eriocaulon carsonii

We investigated the relative importance of above- and below-ground competition by reeds (Phragmites australis (Cav.) Trin. ex Steud) on the growth rate of Eriocaulon carsonii F.Muell. subsp. carsonii, an endangered plant threatened by reeds on artesian springs in Australia. Soil-filled buckets containing E. carsonii were frequently watered to simulate artesian spring conditions and subject to three treatments: (1) no Phragmites (control), (2) Phragmites (ABG), and (3) Phragmites with shoots tied back (BG). After thirteen months, Phragmites mean below-ground biomasses had increased to c. 3 kg m⁻² and mean above-ground biomasses to c. 1 kg m⁻². After the same period, mean root biomass of E. carsonii plants was significantly lower in buckets subject to both Phragmites treatments compared with control plants, as was E. carsonii foliage area. Comparison of the two Phragmites treatments indicated that below-ground competition was the primary cause of this reduced growth in E. carsonii. The vulnerability of E. carsonii to competitive exclusion by P. australis is in part due to the highly synchronized phenologies of the two species.     

Benthic decomposition of Ulva lactuca: A controlled laboratory experiment

The degradation of an Ulva lactuca mat (0.2 kg dw m⁻²) was studied in a controlled flow-through mesocosm for 31 d. Sediment chambers without U. lactuca served as controls. Fluxes of ∑CO₂, O₂, inorganic nitrogen, and urea were determined during the incubation period in addition to sulfate reduction rates, POC and PON content, enumeration of specific bacterial populations and evaluation of the physiological state of the added U. lactuca thalli. After U. lactuca addition to the chambers, there was an immediate increase in the efflux of ∑CO₂ from 11 to 27 mmol-C m⁻² d⁻¹ and a concomitant increase in O₂ uptake from 11 to 23 mmol m⁻² d⁻¹. These effluxes remained elevated throughout the incubation period. In contrast, the NH₄⁺ efflux increased from 0.1 to 1.8 mmol NH₄⁺ m⁻² d⁻¹ during the first 3 d of incubation, followed by 6 d with a constant efflux rate, after which time it decreased gradually to 0.3 mmol NH₄⁺ m⁻² d⁻¹ by the end of the experiment. In total, NH₄⁺accounted for 83% of the total nitrogen efflux after addition of U. lactuca. During the 31 d incubation period there was a continuous colonization of the thalli by bacteria. Sulfate reducers associated with the thalli accounted for 3% of the carbon oxidation on day 31. The molar C:N ratio in mineralization products (the ratio between the efflux of ∑CO₂ and NH₄⁺ + NO₂⁻ + NO₃⁻) increased from 15 mol mol⁻¹ at day 11 after U. lactuca addition to >80 mol mol⁻¹ by the end of the incubation. Since the C:N ratio in the mineralization products was much higher than the original thallus material (8.9 mol mol⁻¹) it is probable that a preferential incorporation of NH₄⁺ into the increasing bacterial biomass occurred. The nitrogen for bacterial growth was most likely obtained from degradation of U. lactuca thalli as there was no stimulation of urea-N turnover in the sediment during incubation. The net increase in bacteria cell number in the 18-mm thick thallus layer was estimated to be 7.6 × 10⁹ to 2.4 × 10¹⁰ bacterial cells cm⁻³. In contrast, the bacterial cell number remained constant in the −Ulva incubations.     

Particle reworking and solute transport by the sediment-living polychaetes Marenzelleria neglecta and Hediste diversicolor

This experimental study quantified and compared particle-mixing and solute transport by the polychaetes Marenzelleria neglecta (2 g ww, 3200 ind. m^− 2) and Hediste diversicolor (2 g ww, 800 ind. m^− 2) in Baltic Sea sediments. Particle tracers (luminophores) were added to the sediment surface and their vertical distribution in the sediment was measured after 10 d. The rate of particle mixing was quantified using a gallery-diffusion model calculating the biodiffusion coefficient D_b and the non-local transport parameter r. Bioirrigation was measured by adding an inert solute tracer (bromide) to the overlying water 1, 1.5 and 2 d before the end of the experiment, and quantified by calculating the net bromide flux and fitting the bromide profiles to a 1D diffusion model providing an apparent biodiffusion coefficient D_a. The two polychaete worms displayed similar particle-mixing and solute transport efficiencies (based on total biomass) despite different modes of bioturbation. However, H. diversicolor was a more efficient particle-reworker and M. neglecta a more efficient bioirrigator, on an individual level. H. diversicolor buried a higher percentage (13%) of luminophores below the top 0.5 cm surface layer than M. neglecta (6%). D_b did not differ between the two species (2.4 × 10^− 3 cm² d^− 1) indicating a similar rate of diffusive mixing of the top sediment, however, the non-local transport parameter r was 2.5 y^− 1 for H. diversicolor and zero for M. neglecta, suggesting no significant particle-transport below the biodiffusive layer by M. neglecta. The average individual net bromide fluxes obtained were ca. 0.01 mL min^− 1 for H. diversicolor and 0.003 mL min^− 1 for M. neglecta, corresponding to an area-specific rate of ca. 12 L m^− 2 d^− 1 at the used densities. D_a did not differ between the two polychaetes, suggesting a higher individual solute exchange efficiency of M. neglecta considering the much higher ventilation rates reported for H. diversicolor than for Marenzelleria sp. The ongoing colonization of Baltic Sea sediments by M. neglecta at high densities may thus lead to an enhanced soluble release of both nutrients and contaminants. These results add information to the understanding of the potential effects of the invasion of M. neglecta on sediment biogeochemistry when competing with and/or replacing native species.     

Community metabolism and buffering capacity of nitrogen in a ruppia cirrhosa meadow

Fluxes of oxygen, inorganic nitrogen (DIN) and denitrification (isotope pairing) were measured from January 1997 to February 1998 via intact cores incubation in a shallow brackish area within the eutrophic Valli di Comacchio (northern Adriatic coast, Italy). Rates were measured in the light and in the dark in sediments colonized by the rooted macrophyte Ruppia cirrhosa and in adjacent sediments with benthic microalgae. Ruppia biomass (25-414 g DW m^− 2) exhibited a seasonal evolution whilst that of microphytobenthos (12-66 mg chl a m^− 2) was more erratic. Net (NP) and gross (GP) primary productivity was 1.15 and 6.89 mol C m^− 2y^− 1 for bare and 25.4 and 51.7 mol C m^− 2y^− 1 for Ruppia vegetated sediments. Nitrogen pools in Ruppia standing stock varied from 43.6 to 631.4 (annual average 201.2) mmol N m^− 2; the macrophyte N content was correlated with DIN concentration in the water column. Estimated N pool in microphytobenthos was one order of magnitude lower (from 2.4 to 14.5 mmol N m^− 2, annual average 7.2). Theoretical DIN assimilation calculated from NP was 127.8 and 1112.6 mmol N m^− 2y^− 1 whilst that calculated from GP was 765 and 2282 mmol N m^− 2y^− 1 for microphytobenthos and Ruppia respectively. Measured annual fluxes of DIN were 974.6 and − 577 mmol N m^− 2y^− 1 in bare and Ruppia vegetated sediments meaning that the two sites were a source and sink for DIN and that from 25 to 50% of Ruppia annual DIN requirements came from the water column. During the period of this study total denitrification was lower in the macrophyte colonized (92.3 mmol N m^− 2y^− 1) compared to bare sediments (163.3 mmol N m^− 2y^− 1) as a probable consequence of higher competition between denitrifiers and phanerogams. At both sites the ratio between denitrification of water column nitrate (D_W) and denitrification coupled to nitrification (D_N) was >1.6 due to little oxygen penetration in reducing sediments (< 1.2 mm) and scarce nitrification activity. D_W (0-35 µmol N m^− 2h^− 1) was significantly correlated with water column NO₃⁻  (2-16 µM). Theoretical DIN assimilation to denitrification ratio varied from 12.0 to 24.8 for Ruppia vegetated and from 0.8 to 4.7 for unvegetated sediments.At Valle Smarlacca, Ruppia may influence nitrogen cycling by incorporating large DIN pools in biomass which is scattered in surrounding areas and fuels intense bacterial activity. With increasing anthropogenic nutrient input and insignificant organic matter export in the open sea the already severe eutrophic conditions are enhanced and may accelerate the decline of the macrophyte meadow.     

Effect of a formulation of Bacillus firmus on root-knot nematode Meloidogyne incognita infestation and the growth of tomato plants in the greenhouse and nursery

Bacillus firmus, commercial WP formulation (BioNem) was evaluated against the root-knot nematode Meloidogyne incognita in a laboratory, greenhouse and under field conditions on tomato plants. In the laboratory tests, an aqueous suspension of BioNem at 0.5%, 1%, 1.5% and 2% concentration reduced egg hatching from 98% to 100%, 24-days after treatment. Treatment of second-stage juveniles with 2.5% and 3% concentration of BioNem, caused 100% inhibition of mobility, 24 h after treatment. In the green house trials, BioNem applied at 8 g/pot (1200 cc soil) planted with a tomato seedlings reduced gall formation by 91%, final nematode populations by 76% and the number of eggs by 45%. Consequently, plant height and biomass was increased by 71% and 50%, respectively, compared to the untreated control, 50-days after treatment application. Application of BioNem at 16 g/pot was phytotoxic to plants. In the field trails, BioNem applied at 200 and 400 kg ha⁻¹ was effective in reducing the number of galls (75-84%), and increased shoot height (29-31%) and weight (20-24%) over the untreated control, 45-days after treatment. Our results indicate that B. firmus is a promising microorganism for the biological control of M. incognita in tomato pots.     

Understanding the potential effects of water regime and salinity on recruitment of Melaleuca ericifolia Sm.

Although many emergent wetland plants may readily tolerate rapid changes in flooding and drying under freshwater conditions, their tolerance to dynamic water regimes may be compromised by salinity. Melaleuca-dominated woodlands occur naturally in Australia, south-east Asia and New Caledonia. Coastal wetlands dominated by Swamp paperbark (Melaleuca ericifolia) (Myrtaceae), native to south-east Australia, are commonly degraded as a consequence of altered water regime and salinity. This study simulates the release of M. ericifolia seeds from the aerial canopy under a range of water regime and salinity scenarios to determine conditions limiting sexual recruitment. Plant growth and survival were examined following seed release under two static water regimes (moist and flooded sediment) and two dynamic water regimes (simulated drawdown—“flooded-moist” and simulated re-flooding—“moist-flooded”). All water regimes, excluding the continuously flooded regime, were examined at three salinities: 0.1 dS m⁻¹ (fresh), 8 dS m⁻¹ and 16 dS m⁻¹, over a 50-day period commencing 44 days after the seeds were sown. The flooded treatment was examined at 0.1 dS m⁻¹ only, to confirm that flooding prohibits establishment of M. ericifolia. Seed and seedlings were positively buoyant and establishment was limited to moist soil. Flotation of seedlings in the flooded-moist treatment, however, did not inhibit subsequent establishment upon moist soil, even at the highest salinity of 16 dS m⁻¹. Growth, but not survival, was reduced by salinities of 8 dS m⁻¹ and 16 dS m⁻¹ in the moist treatment. Flotation of seedlings in saline water in the flooded-moist treatment did not reduce growth or survival compared with fresh water. Survival of seedlings in the moist-flooded treatment was lower in the freshwater and 16 dS m⁻¹ treatment compared with the moist treatment, but not at 8 dS m⁻¹. These findings suggest that water regime influences establishment of young M. ericifolia plants more strongly than does salinity, at least up to ∼1/3 seawater and in the short term (<2 months). Seedlings are likely to establish during a drawdown where the soil is exposed at salinities of ≤16 dS m⁻¹. In contrast, premature re-flooding of seedlings, even with fresh water, will compromise survival.     

Evaluation of selenite bioremoval from liquid culture by Enterococcus species

The genus Enterococcus belong to the genera of bacteria that produce lactic acid and can confer health benefits to living organisms. Selenium (Se) is an essential micronutrient for humans and animals. Thirty-six Enterococcus species isolated from dairy products were screened for Se(IV) sorption capacity for use as a probiotics in animal nutrition. Several isolates grew luxuriantly and significantly removed Se(IV) from Se(IV) amended medium. Two isolates, LAB 14 and LAB 18, identified by 16S rRNA gene sequence analysis as Enterococcus faecalis (98% nucleotide sequence similarity) and Enterococcus faecium (97% nucleotide sequence similarity), respectively, were selected for further studies. The two isolates grew optimally and removed selenium at initial pH 7.0. Optimum removal of Se(IV) from the medium was recorded at 25 °C. Time course studies showed that after 8 h of incubation LAB 14 and LAB 18 cultures displayed the highest biomass production and Se(IV) bioremoval and most selenite in culture depleted in 24 h. At initial concentrations of 10 mg L⁻¹ and 60 mg L⁻¹, E. faecium (LAB 18) removed 9.91 mg L⁻¹ and 59.70 mg L⁻¹, respectively after 24 h. Similar Se(IV) bioremoval capacity was recorded with E. faecalis (LAB 14). Substantial amount of Se was detected in biomass of E. faecium (0.4599 mg g⁻¹ of dry weight) and E. faecalis (0.4759 mg g⁻¹ of dry weight). The significant uptake and transformation of Se(IV) by the Enterococcus species observed in this study suggest that they can be used to deliver dietary Se through feed augmentation with Se(IV)-enriched Enterococcus biomass.     

Chemical profile of the North American native Myriophyllum sibiricum compared to the invasive M. spicatum

Myriophyllum spicatum L. is a nonindigenous invasive plant in North America that can displace the closely related native Myriophyllum sibiricum Komarov. We analyzed the chemical composition (including: C, N, P, polyphenols, lignin, nonpolar extractables, and sugars) of M. spicatum and M. sibiricum and determined how the chemistry of the two species varied by plant part with growing environment (lake versus tank), irradiance (full sun versus 50% shading), and season (July through September). M. spicatum had higher concentrations of carbon, polyphenols and lignin (C: 47%; polyphenols: 5.5%; lignin: 18%) than M. sibiricum (C: 42%; polyphenols: 3.7%; lignin: 9%) while M. sibiricum had a higher concentration of ash under all conditions (12% versus 8% for M. spicatum). Apical meristems of both species had the highest concentration of carbon, polyphenols, and tellimagrandin II, followed by leaves and stems. Tellimagrandin II was present in apical meristems of both M. spicatum (24.6 mg g⁻¹ dm) and M. sibiricum (11.1 mg g⁻¹ dm). Variation in irradiance from 490 (shade) to 940 (sun) μmol of photons m⁻² s⁻¹ had no effect on C, N, and polyphenol concentrations, suggesting that light levels above 490 μmol of photons m⁻² s⁻¹ do not alter chemical composition. The higher concentration of polyphenols and lignin in M. spicatum relative to M. sibiricum may provide advantages that facilitate invasion and displacement of native plants.     

Vermistabilization of primary sewage sludge

An integrated composting-vermicomposting process has been developed for utilization of primary sewage sludge (PSS). Matured vermicompost was used as bulking material and a source of active microbial culture during aerobic activated composting (AAC). AAC resulted in sufficient enrichment of bulking material with organic matter after 20 cycles of recycling and mixing with PSS and produced materials acceptable for vermicomposting. Vermicomposting caused significant reduction in pH, volatile solids (VS), specific oxygen uptake rate (SOUR), total organic carbon (TOC), C/N ratio and pathogens and substantial increase in electrical conductivity (EC), total nitrogen (TN) and total phosphorous (TP) as compared to compost. Environmental conditions and stocking density have profound effects on vermicomposting. Temperature of 20 °C with high humidity is favorable environmental condition for vermicomposting employing Eisenia fetida. Favorable stocking density range for vermiculture is 0.5-2.0 kg m⁻² (optimum: 0.5 kg m⁻²) and for vermicomposting is 2.0-4.0 kg m⁻² (optimum: 3.0 kg m⁻²), respectively.     

Vegetation patterns and spontaneous regression of Caulerpa taxifolia (Vahl) C. Agardh in Malinska (Northern Adriatic,Croatia)

The green alga Caulerpa taxifolia was recorded at Malinska in 1994 and this actually represents the highest northern latitude (45°7′30″N) at which this invasive alga has been found in the world. The alga was widespread at four sites from which it was eradicated by suction pumps during 1996 and 1997. However, it immediately and intensively recolonized all but one site. Throughout 1998 and 1999 the renewed vegetation showed consistent seasonal patterns. The alga nearly disappeared in April and May while regenerating from over-wintering parts of the thalli in summer. The maximum development occurred in autumn and winter with values of biomass (around 200 g dry weight m⁻²) and frond number (around 2000 m⁻²) generally lower than those reported for the north-western Mediterranean. Values for the frond length (10–18 cm) were in the same range as those in the north-western basin. Throughout 1998 and 1999 the biomass was closely correlated to frond number and length (adjusted R² = 0.90). During the following years C. taxifolia entered a phase of regression. The total colonized area, which amounted to several thousands of square metres in 1998, spontaneously declined in 2000 and 2001 so that only several thalli were found in 2004 during a detailed survey of the settlement. No major changes in winter seawater temperatures, ranging from 9.5 to 10.5 °C, were observed in the area from 1994 to 2004. Thus, other unknown processes could likely play a role on specific vegetation patterns of C. taxifolia in Malinska. Accordingly, it is difficult to explain why the still surviving thalli did not proliferate during the favourable summer–autumn period.     

Control of Grapholita molesta (Busck, 1916) (Lepidoptera: Tortricidae) with entomopathogenic nematodes (Rhabditida: Heterorhabditidae,Steinernematidae) in peach orchards

Oriental fruit moth Grapholita molesta (Busck, 1916) (Lepidoptera: Tortricidae) is considered a major pest in temperate fruit trees, such as peach and apple. Entomopathogenic nematodes (EPNs) are regarded as viable for pest management control due to their efficiency against tortricid in these trees. The objective of this study was to evaluate the effectiveness of native EPNs from Rio Grande do Sul state against pre-pupae of G. molesta under laboratory and field conditions. In the laboratory, pre-pupae of G. molesta were placed in corrugated cardboard sheets inside glass tubes and exposed to 17 different EPNs strains at concentrations of 6, 12, 24, 48 and 60 IJs/cm² and maintained at 25 °C, 70 ± 10% RH and photophase of 16 h. Insect mortality was recorded 72 h after inoculation of EPNs. Steinernema rarum RS69 and Heterorhabditis bacteriophora RS33 were the most virulent strains and selected for field application (LC₉₅ of 70.5 and 53.8 IJs/cm², respectively). Both strains were highly efficient under field conditions when applied in aqueous suspension directed to larvae on peach tree trunk, causing mortality of 94 and 97.0%, respectively.     

Growth and annual production of the brown alga Laminaria japonica (Phaeophyta, Laminariales) introduced into the Uwa Sea in southern Japan

The brown alga Laminaria japonica is distributed from southern Hokkaido to the northeastern Honshu in Japan. Recently, aquaculture of L. japonica has expanded to the southern coast of Japan and to China along the East China Sea. In order to elucidate the growth, biomass and productivity of L. japonica in a subtropical area, we cultivated and examined it in the Uwa Sea, in southwestern Japan over a period of 2 years. The seawater temperature ranged from 13.8 to 26.8 °C in 2001/2002 and from 13.1 to 27.2 °C in 2002/2003. In 2001/2002, the maximum density, maximum mean length and maximum mean wet wt. of L. japonica were 59.7 ± 28.0 ind. 50 cm^− 1 (mean ± S.D.), 187.5 ± 82.7 cm (360 cm in the largest individual) and 130.1 ± 94.6 g wet wt., respectively. In 2002/2003, these values were 94.7 ± 22.2 ind. 50 cm^− 1, 159.3 ± 74.4 cm (300 cm in the largest individual) and 95.2 ± 69.5 g wet wt., respectively. Thus, the length and weight increased when the density was low (2001/2002), and the length and weight decreased when the density was high (2002/2003). The maximum biomass was estimated to be 7200 ± 3400 g wet wt. 50 cm^− 1 in 2001/2002 and 7300 ± 2000 g wet wt. 50 cm^− 1 in 2002/2003. Annual production was estimated to be 33.3 kg wet wt. m^− 1 year^− 1 in 2001/2002 and 34.0 kg wet wt. m^− 1 year^− 1 in 2002/2003. The present study indicates that the annual production of L. japonica per rope of 1 m at Uwajima Bay, the Uwa Sea corresponded to 1.1-2.2 m² of that of Hokkaido in their native area. Thus, the present study indicates that L. japonica is highly adaptable because it is able to keep a high level of productivity when grown in water with a high temperature.     

Purification and characterization of two extracellular endochitinases from Massilia timonae

Two extracellular chitinases (designated as Chi-56 and Chi-64) produced by Massilia timonae were purified by ion-exchange chromatography, ammonium sulfate precipitation, and gel-filtration chromatography. The molecular mass of Chi-56 was 56 kDa as determined by both SDS-PAGE and gel-filtration chromatography. On the other hand, Chi-64 showed a molecular mass of 64 kDa by SDS-PAGE and 28 kDa by gel-filtration chromatography suggesting that its properties may be different from those of Chi-56. The optimum temperature, optimum pH, pI, K_m, and V_max of Chi-56 were 55 °C, pH 5.0, pH 8.5, 1.1 mg mL⁻¹, and 0.59 μmol μg⁻¹ h⁻¹, respectively. For Chi-64, these values were 60 °C, pH 5.0, pH 8.5, 1.3 mg mL⁻¹, and 1.36 μmol μg⁻¹ h⁻¹, respectively. Both enzymes were stimulated by Mn²⁺ and inhibited by Hg²⁺, and neither showed exochitinase activity. The N-terminal sequences of Chi-56 and Chi-64 were determined to be Q-T-P-T-Y-T-A-T-L and Q-A-D-F-P-A-P-A-E, respectively.     

Nutritional value and intake of aquatic ferns (Azolla filiculoides Lam. and Salvinia molesta Mitchell.) in sows

Aquatic ferns (AFs) such as Azolla filiculoides and Salvinia molesta are grown on swine lagoons in the tropics and used in diets for pigs. The present work is aimed at evaluating their potential as feed ingredients for sows. When presented with ad libitum AFs, gilts weighing 110 ± 14 kg (mean ± SD), were able to ingest 9.1–9.7 kg fresh AF per day (from 597 to 630 g dry matter (DM) per day) and from 1240 to 1428 g DM per day when presented in a dry, ground form. A digestibility study was conducted, using sows weighing 213 ± 9 kg (mean ± SD), which were fed diets containing maize, soybean meal and 0, 150 or 300 g AF kg⁻¹ diet. The presence of AFs had a negative impact on the faecal digestibility of the crude protein, NDF and energy content of the whole diet (P<0.001) and on the ileal protein digestibility, especially with 300 g AFs kg⁻¹ diet. The level of AFs in the diet had no effect on stomach weight (P>0.05) but increased the weight of the rest of the gastrointestinal tract (P<0.001). The rate of AF fibre fermentation in the pig large intestine was measured using an in vitro gas test. The rates were much lower than tropical tree foliage, which can also be used in pig diets in the tropics. This could partly explain the low apparent digestibility of AFs in pigs. In conclusion, the inclusion level of AFs in rations for sows should be limited to 150 g AFs kg⁻¹ diet due to the low digestibility and energy density, as well as the negative impact on the digestibility of the whole diet.     

Sorgoleone,a sorghum root exudate: Algicidal activity and acute toxicity to the ricefish Oryzias latipes

The discovery of natural and natural-based compounds has resulted in its application as an alternative to synthetic algicides to control harmful algae in aquatic systems. Of the many natural-product-based algicides, sorgoleone, a natural plant product from Sorghum bicolor root exudates has been investigated for its controlling effect on different algal species and its acute fish toxicity. Growth of the blue green algal species Microcystis aeruginosa Kützing was completely inhibited by the crude methanol extract of sorghum root at 20 μg mL⁻¹. The most noticeable inhibition was observed in the bioassay of n-hexane soluble extract, where 98% growth inhibition occurred in M. aeruginosa at the concentration of 1.25 μg mL⁻¹. Sorgoleone very effectively controlled blue green algae inhibiting 97% of M. aeruginosa at 0.5 μg mL⁻¹ and 99% of Anabaena affinis Lemmermann at 4 μg mL⁻¹. In contrast, inhibition of the green algae species Chlorella vulgaris Beijerinck and Scenedensmus spp. at 16 μg mL⁻¹ sorgoleone was 87 and 68%, respectively. There were no mortalities or adverse effects observed in any of the fish exposed to water control, solvent control, and a nominal concentration of 1 μg mL⁻¹ during the test period. The no observed effect concentration (NOEC) value was 1.5 μg mL⁻¹ for the tested fish (O. latipes). Sorgoleone can be considered as an effective and an ecologically and environmentally sustainable approach to controlling harmful algae.     

Temporary drought can selectively suppress Schoenoplectus mucronatus in rice

Outdoor pot experiments were conducted in California to quantify differences in rice and Schoenoplectus mucronatus susceptibility to drought and to identify morphological and physiological traits that would favor rice over S. mucronatus under drought. Plants were grown in flooded soil for approximately 5 weeks, and then subjected to different drought periods after which pots were re-flooded. Chlorophyll fluorescence assays revealed that rice and S. mucronatus Fv/Fm first became <0.8 after leaf water potential (Ψ_leaf) had decreased to approximately −4 MPa and −2 MPa, respectively. Thus, by suffering less photosynthetic damage from drought, rice had better recovery after re-flooding than S. mucronatus. When drought reduced Ψ_leaf to −3 MPa, S. mucronatus re-growth was nearly suppressed but that of rice was unaffected. Rice plants depleted soil moisture 1.6 faster than S. mucronatus due to larger and deeper roots and a high water-spending strategy (when Ψ_leaf decreased from approximately −0.5 MPa to −2.5 MPa, ¹³δ increased from −27.8 to −27.4 and from −28.1 to −26.0 for rice and S. mucronatus, respectively). Rice under interspecific competition sustained its Ψ_leaf by extracting more water from greater depths, while causing severe moisture stress and photosynthetic damage to S. mucronatus. Thus temporary drought enhanced rice competitiveness over S. mucronatus, supporting the concept of using brief drought as a tool for S. mucronatus suppression in rice. The Ψ_leaf developed by the end of the drought period predicted rice yields (R² = 0.77, P < 0.0001) and the capacity of S. mucronatus to recover from drought upon irrigation resumption (R² = 0.62, P < 0.001). Brief (8-10 d) drought imposed on 5-week-old rice did not significantly depress late-season rice biomass growth or grain yields, while S. mucronatus never fully recovered from drought. Rice yields were only reduced after Ψ_leaf reached values below approximately −2.5 MPa. Longer drought (∼20 d) delayed maturity and reduced rice yields by approximately 60-80%. The dry-down approach could help suppress weeds similar to S. mucronatus in organic rice where premium prices can compensate for lower grain yield.     

Continuous culture of the microalgae Schizochytrium limacinum on biodiesel-derived crude glycerol for producing docosahexaenoic acid

Crude glycerol is a major byproduct of the biodiesel industry; previous research has proved the feasibility of producing docosahexaenoic acid (DHA, 22:6 n − 3) through fermentation of the algae Schizochytrium limacinum on crude glycerol. The objective of this work is to investigate the cell growth kinetics, substrate utilization efficiency, and DHA production of the algae through a continuous culture. Steady-state biomass yield, biomass productivity, growth yield on glycerol, specific glycerol consumption rate, and fatty acid composition were investigated within the range of dilution rate (D) from 0.2 to 0.6 day⁻¹, and the range of feed crude glycerol concentration (S₀) from 15 to 120 g/L. The maximum specific growth rate was determined as 0.692 day⁻¹. The cells had a true growth yield of 0.283 g/g but with a relatively high maintenance coefficient (0.2216 day⁻¹). The highest biomass productivity of 3.88 g/L-day was obtained at D = 0.3 day⁻¹ and S₀ = 60 g/L, while the highest DHA productivity (0.52 g/L-day) was obtained at D = 0.3 day⁻¹ and S₀ = 90 g/L due to the higher DHA content at S₀ = 90 g/L. The biomass and DHA productivity of the continuous culture was comparable to those of batch culture, while lower than the fed-batch culture, mainly because of the lower DHA content obtained by the continuous culture. Overall, the results show that continuous culture is a powerful tool to investigate the cell growth kinetics and physiological behaviors of the algae growing on biodiesel-derived crude glycerol.     

Physiological,morphological and anatomical trait variations between winter and summer leaves of Cistus species

Morphological, anatomical and physiological summer and winter leaf traits of Cistus incanus subsp. incanus, C. salvifolius and C. monspeliensis growing at the Botanical garden of Rome were analyzed. With regard to differences between summer and winter leaves of the considered species, leaf thickness (L) was 21% higher in summer than in winter leaves (mean of the considered species) and this increase was mostly the result of the increased palisade parenchyma thickness over the spongy parenchyma one (24 and 16% higher in summer than in winter leaves, respectively). Leaf mass area (LMA) and leaf tissue density (LTD) were 38% and 17% higher in summer than in winter leaves, respectively (mean of the considered species). The photosynthetic rate (P_N), stomatal conductance (g_s) and chlorophyll content (Chl) of summer leaves were 54%, 17% and 14% lower, respectively, than in winter leaves. C. monspeliensis summer leaves had the highest LMA, LTD, adaxial cuticle thickness (14.6 ± 1.8 mg cm⁻², 1091 ± 94 mg cm⁻³, and 5.8 ± 1.7 μm, respectively) and the lowest mesophyll intercellular spaces (f_ias 38 ± 3%). Moreover, C. monspeliensis had the highest P_N in summer (2.6 ± 0.1 μmol m⁻² s⁻¹) and C. incanus the highest P_N and WUE (84% and 59% higher than the other species) in the favorable period, associated to a higher f_ias (42 ± 2%). C. salvifolius had the highest P_N (54% higher than the other species) in winter. The plasticity index could allow a better interpretation of the habitat preference of the considered species. The physiological plasticity (PI_p = 0.39, mean value of the considered species) was higher than the morphological (PI_m = 0.22, mean value) and anatomical (PI_a = 0.13, mean value) plasticity. Moreover, among the considered species, C. salvifolius and C. incanus are characterized by a larger PI_a (0.14, mean value) which seems to be correlated with their wider ecological distribution and the more favorable conditions of the environments where they naturally occur. The highest PI_m (0.29) of C. monspeliensis indicates that it can play a high adaptive role in highly stressed environments, like fire degraded Mediterranean areas in which it occurs.