Diversification of African tree frogs (genus Leptopelis) in the highlands of Ethiopia

The frog genus Leptopelis is composed of ~50 species that occur across sub‐Saharan Africa. The majority of these frogs are typically arboreal; however, a few species have evolved a fossorial lifestyle. Most species inhabit lowland forests, but a few species have adapted to high elevations. Five species of Leptopelis occupy the Ethiopian highlands and provide a good opportunity to study the evolutionary transition from an arboreal to a fossorial lifestyle, as well as the diversification in this biodiversity hot spot. We sequenced 14 nuclear and three mitochondrial genes, and generated thousands of SNPs from ddRAD sequencing to study the evolutionary relationships of Ethiopian Leptopelis. The five species of highland Leptopelis form a monophyletic group, which diversified during the late Miocene and Pliocene. We found strong population structure in the fossorial species L. gramineus, with levels of genetic differentiation between populations similar to those found between arboreal species. This could indicate that L. gramineus is a complex of cryptic species. We propose that after the original colonization of the Ethiopian highlands by the ancestor of the L. gramineus group, episodes of vicariance fragmented the ancestral populations of this group. We also report the re‐evolution of arboreality in L. susanae, which evolved from a fossorial ancestor, a rare ecological switch in frogs that had previously been reported only once.     

修复白洋淀镉污染水体的沉水植物筛选试验

为了筛选出适宜修复白洋淀镉(Cd)污染水体的沉水植物,该研究通过室内模拟试验,分析了四种沉水植物黑藻、狐尾藻、金鱼藻和菹草对Cd的耐受性及对底泥Cd的富集和迁移能力。结果表明:(1)通过毒性测试研究,Cd对黑藻、狐尾藻、金鱼藻及菹草的4 d-EC₅₀(半数抑制浓度)分别为0.51、0.81、0.03、0.12 mg·L^-1,狐尾藻对Cd的耐性最强,黑藻次之,金鱼藻对Cd的耐性最低; 四种沉水植物对Cd的最大富集量分别为27.89、15.28、22.54、32.74 g·kg^-1,菹草对Cd的富集能力最强,黑藻次之,狐尾藻对Cd的富集能力最低。(2)通过Cd污染底泥修复研究,黑藻、狐尾藻和菹草体内Cd富集量整体表现为根>叶片和茎(P<0.05); 地上部、根对Cd的富集能力分别表现为黑藻>菹草>狐尾藻,菹草>黑藻>狐尾藻; 三种沉水植物对Cd的迁移能力则表现为黑藻>狐尾藻>菹草。总之,黑藻对底泥中Cd富集和迁移能力均较强,且耐性较高,是最适合修复白洋淀Cd污染水体的沉水植物。     

Comparison of sperm viability with seminal plasma metal levels

This study compares the semen levels of lead (Pb), cadmium (Cd), and aluminum (Al) in relation to live sperm in semen samples from 64 apparently healthy men. The measured levels were separated into live sperm count tertiles (<25% [18 subjects], 25–50% [26 subjects], and >50% [20 subjects]). The mean ± SD for each group was calculated, and the difference between the means of the high and low tertiles were compared by ANOVA. Significant differences were observed between the high and low live sperm groups for Pb (p < 0.01) and Al (p < 0.05), but not Cd. Spearman’s rank correlation between sperm viability and the semen plasma metal levels showed a direct relation to Mg (p < 0.05). However, there was an inverse relation to lead (p < 0.001), cadmium (p < 0.01), and aluminum (p < 0.01). There was no significant correlation between Ca and Zn. Linear regression between the live sperm counts and semen level of the three metals show that metal levels were inversely correlated with the percentage of live sperm (p < 0.001, <0.01). Apparently, the presence of these metals in the environment and in seminal plasma exerts a toxic effect on sperm.     

IN SITU ALLELOPATHIC POTENTIAL OF MYRIOPHYLLUM VERTICILLATUM (HALORAGACEAE) AGAINST SELECTED PHYTOPLANKTON SPECIES1

The potential allelopathic impact of Myriophyllum verticillatum L. under in situ conditions was determined in a series of field and laboratory experiments. Coexistence experiments were performed in a lake dominated by M. verticillatum (Van Goor) Meffert where we exposed three unialgal phytoplankton cultures in dialysis tubes to macrophyte exudates regularly during the vegetated period. Plant content and exudation of polyphenolic compounds were determined, and the inhibitory activity of polyphenol‐containing extracts was tested in bioassays with cyanobacteria. To account for possible resource interference, we monitored growth and photosynthesis of phosphorus‐limited and unlimited cyanobacterium Limnothrix redekei in dialysis tubes exposed to M. verticillatum in aquaria. A high allelopathic potential of M. verticillatum was concluded from high tissue concentrations of total phenolic compounds of 6%–12% of dry matter, the demonstrated release of bioactive polyphenols into the surrounding medium, and the inhibition of cyanobacteria by extracts. We could not unambiguously demonstrate the exudation of polyphenols by M. verticillatum in situ due to interference with allochthonous humic compounds. In laboratory experiments, L. redekei exhibited significantly reduced maximum relative electron transport rates when co‐cultivated in dialysis tubes with M. verticillatum. The field dialysis tube experiment confirmed this result, accompanied by a decline of chl a and PSII activity for L. redekei and the diatom Stephanodiscus minutulus (Kütz.) Greve et Möller, but not for the green alga Scenedesmus armatus Chodat in August. At other times, either no effects or stimulatory effects were observed with all species. Nutrient limitation of the target species may have masked allelopathic effects, and M. verticillatum may have enhanced phytoplankton growth due to phosphorus leakage.     

Consumer-driven nutrient release to the water by a small omnivorous fish enhanced ramet production but reduced the growth rate of the submerged macrophyte Vallisneria denseserrulata (Makino) Makino

Small fish are highly associated with submerged macrophytes but may potentially hamper their growth due to nutrient excretion that stimulate growth of phytoplankton and periphyton growth. We conducted a mesocosm experiment to elucidate the effects of the small omnivore Chinese bitterling Acheilognathus macropterus on the growth of phytoplankton, periphyton and the submerged macrophyte Vallisneria denseserrulata. The treatments were fishless as well as low (LF) and high (HF) fish density. We found that the concentrations of nutrients and the phytoplankton biomass increased substantially in both fish treatments, leading to a significantly higher light attenuation compared with the control. Moreover, bitterling substantially enhanced the biomass of periphyton on plant leaves. Consequently, the relative growth rate (RGR) of V. denseserrulata was significantly suppressed in HF, while RGR in the LF treatment did not differ significantly from the controls. However, the bitterling also stimulated the ramet production of V. denseserrulata, significantly. Our results indicate that Chinese bitterling reduce the RGR of V. denseserrulata under high fish density condition. Therefore, the density of Chinese bitterling should be kept low in order to reduce the negative effects of the fish on the RGR of submerged macrophytes (e.g. V. denseserrulata), when restoring lakes by plant transplantation.

     

Biomass allocation and nutrient use in fast-growing woody and herbaceous perennials used for phytoremediation

This study assessed the suitability of two deciduous woody perennials (Salix spp. and Populus spp.) and two summer green herbaceous perennials (Phragmites australis and Urtica dioica) for purification of nutrient enriched wastewater. The main hypothesis tested was that species with a particular trait combination of high relative growth rate (RGR), low nutrient productivity (A) and high mean residence time (MRT) of nutrients would be most effective in accumulating nutrients. The nitrogen and phosphorus use efficiency at the whole plant level was analysed. Four treatments comprising two possible phytoremediation substrates (municipal wastewater and landfill leachate) and two control plant nutrition situations (balanced nutrient solution and pure water) were applied in four replications to the four plant species. Generally, all four species studied showed a high RGR and a low P productivity in the balanced nutrient solution treatment, while the opposite (low RGR and high P productivity) was seen in the phytoremediation substrate and pure water treatments. The general conclusion is that if P is present in marginal proportions in the wastewater, a vegetation filter with Phragmites would have an advantage since biomass and nutrient accumulation in Phragmites does not decrease as much during phytoremediation as that in deciduous woody perennials.     

Competition between two submersed aquatic macrophytes, Potamogeton pectinatus and Potamogeton gramineus, across a light gradient

Competitive abilities of Potamogeton pectinatus L. and Potamogeton gramineus L. were estimated using additive series experiments at across a gradient of total daily irradiance ranging from 1.2 to 9.7 mol m⁻² day⁻¹. Results for P. gramineus showed that its mean weight per plant was reduced more by the presence of other P. gramineus plants than by changes in the density of P. pectinatus. However, the difference was statistically significant only at the higher light levels examined. In the case of P. pectinatus, P. gramineus exerted a stronger impact on P. pectinatus plants than did other P. pectinatus plants. Coefficients representing interspecific competition were significantly greater than those representing intraspecific competition at higher light levels. These results indicate that P. gramineus was a stronger competitor when light levels were high. They further indicate that at low light levels, there was little evidence that competition was a strong force in determining either species performance. These results support a theory offered by Grime. However, it was possible to predict that P. gramineus would be a stronger competitor based on its light compensation point which was lower than the one for P. pectinatus. This demonstrates the utility of the R* approach proposed by Tilman. Aspects of both approaches may aid ecologists in understanding community structure.     

Accumulation of selenium by different plant species grown under increasing sodium and calcium chloride salinity

High levels of naturally occurring selenium (Se) are often found in conjunction with different forms of salinity in central California. Plants considered for use in phytoremediation of high Se levels must therefore be salt tolerant. Selenium accumulation was evaluated for the following species under increasing salt (NaCl and CaCl) conditions:Brassica napus L. (canola),Hibiscus cannibinus L. (kenaf),Festuca arundinacea L. (tall fescue), andLotus tenuis L. (birdsfoot trefoil). The experimental design was a complete randomized block with four salt treatments of <1, 5, 10, and 20 dS m^-1, four plant species, three blocks, and six replicates per treatment. Ninety days after growing in the respective salt treated soil with a Se concentration of 2 mg Se kg^-1 soil, added as Na₂SeO₄, all plant species were completely harvested. Among the species tested, shoot and root dry matter yield of kenaf was most significantly (p<0.001) affected by the highest salt treatment and tall fescue and canola were the least affected species. Generally there was a decrease in tissue accumulation of Se with increasing salt levels, except that low levels of salinity stimulated Se accumulation in canola. Canola leaf and root tissue accumulated the highest concentrations of Se (315 and 80 mg Se kg^-1 DM) and tall fescue the least (35 and 7 mg Se kg^-1 DM). Total soil Se concentrations all harvest were significantly (p<0.05) lower for all species at all salt treatments. Removal of Se from soil was greatest by canola followed by birdsfoot trefoil, kenaf and tall fescue. Among the four species, canola was the best candidate for removing Se under the tested salinity conditions. Kenaf may be effective because of its large biomass production, while tall fescue and birdsfoot trefoil may be effective because they can be repeatedly clipped as perennial crops.     

Control of Myriophyllum verticillatum L. in Irish canals by turion removal

Myriophyllum verticillatum L. is the single most obstructive aquatic plant in Irish canals. Because of the importance of these canals as national amenities, considerable resource has been directed towards the long-term control of this aggressive plant. A combination of mechanical harvesting and chemical treatment has traditionally been employed to control Myriophyllum growth but these methods have only provided short-term control. Myriophyllum verticillatum reproduces by producing turions between September and November each year. These over-wintering propagules sink to the canal bed where they remain dormant until February. At a trial site on the Royal Canal turions were harvested in November 1994 and 1995, significantly reducing the number of propagules present. Biomass and plant cover with M. verticillatum throughout the 1995 and subsequent growing seasons was dramatically reduced. The implications for weed control programmes, habitat development and amenity usage are discussed.     

Use of Clonostachys rosea against sheep nematodes developing in pastures

The fungus Clonostachys rosea f. rosea has the potential to control gastrointestinal nematodes (GIN) of sheep. A study was conducted using adult Merino sheep. Gender, egg count and initial body weights (BWs) were used to categorise animals into four groups which were randomly assigned to one of four C. rosea dietary treatments. Treatments were mixed with a complete diet and fed to sheep once daily for 10 weeks. There was no effect of treatment on eggs per gram of faeces. However, treatments reduced the number of larvae per gram in faecal cultures (P < 0.001) and larval development (LD) time (P < 0.001). Efficacy of treatments increased (P < 0.001) with time. On Day 70, treatments of 0.25, 0.5 and 1.0 g of C. rosea chlamydospores per kilogram BW reduced LD time by 33, 72 and 89%, respectively, whereas in the control, LD was reduced by only 2.6%. C. rosea significantly (P < 0.001) reduced numbers of third-stage larvae (L₃) found in pastures. Our findings suggest that daily feeding with C. rosea has a potential to reduce larval stages of GIN in pastures.     

Feeding value of field beans (Vicia faba L. var. minor) with and without enzyme containing tannase,pectinase and xylanase activities for broilers

Effects of field beans with various tannin content and exogenous enzyme mixture containing tannase, pectinase and xylanase activities on N-corrected dietary apparent metabolisable energy (AMEn), coefficients of dry matter (DMR) and nitrogen retention (NR), fat digestibility, gastrointestinal tract (GIT) development, jejunal villus morphometry, ileal digesta viscosity and sialic acid were examined. Birds’ growth performance and energy conversion ratio (ECR) were also measured. Birds were fed one of eight mash diets. The Control diet contained as major ingredients wheat (400 g/kg) and soybean meal (SBM) (127 g/kg and 221 g crude protein/kg and 12.83 MJ AMEn/kg. To reduce nutrient density, the Control diet also contained washed sand at 119 g/kg. Another three diets containing 300 g/kg of each of three experimental field bean cultivar samples in replacement for SBM and sand were also mixed. Each diet was fed to nine pens with two male Ross 308 broilers. Diets high in tannin had low AMEn, ECR, DMR and NR (p < 0.001). Feeding field beans increased (p < 0.001) the weights of the pancreas and the proventriculus and gizzard (PG) of the birds. Supplementing diets with the enzyme mixture improved (p < 0.001) feed conversion efficiency, AMEn and all nutrient utilisation coefficients despite the tannins in diets. The enzyme mixture reduced ileal digesta viscosity (p < 0.001) and the weight of pancreas, total GIT and PG (p < 0.05) of the birds. It can be concluded that the feeding value of field beans with different tannin contents may vary when fed to broilers. The supplementation of the enzyme mixture improved the feeding value of diets for broilers. The beneficial effect of the addition of the enzyme mixture seems to be mediated through reduced ileal digesta viscosity and improved nutrient availability.     

Temperature Controls a Dependence of Barley Plant Growth on Mineral Nutrition Level

The effect of temperature regime on growth and other morphological characteristics of barley plants (Hordeum distichum L., cv. Andrei) as dependent on the level of mineral nutrition was investigated in a controlled experiment. Plants were raised hydroponically at a high (0.22 g/(g day)) and low (0.05 g/(g day)) relative rates of the addition of mineral nutrients (R _A). Mineral nutrients were daily added to the nutrient solutions in exponentially increased amounts to provide steady-state plant growth. At the optimum temperature regime (21/17°C, day/night), the plant relative growth rate (RGR) was proportional to the preset R _A during the entire exponential period. Low R _A led to a decrease in the nitrogen content in plants, plant weight, and respiratory activity, as well as to the increase in the relative root weight. Biomass accumulation at lowered temperature regime (13/8°C) and a high R _A was 1.8-fold lower than at optimum temperature regime. Although under these conditions, the ratio of respiration to gross photosynthesis reduced threefold due to the decrease in the respiration rate, RGR of plants was equal to 0.11 ± 0.02 g/(g day), which was twice lower than the preset R _A. These pointed to the decrease in plant ability to maintain a certain ratio of photosynthesis to respiration within a day. At a deficiency of mineral nutrition and low temperature, RGR reached the preset R _A. Plants adapted to lowered temperature by a shift of the temperature optimum of their metabolism (heat production) to lower values. As a whole, a low variability of such growth parameters as RGR, C/N, and root to shoot weight ratio at different R _A and lowered temperatures testified to the lessening of growth limitation by the mineral nutrition.__________Translated from Fiziologiya Rastenii, Vol. 52, No. 3, 2005, pp. 384–391.Original Russian Text Copyright © 2005 by Garmash.     

Using banana to generate lactic acid through batch process fermentation

We evaluated the usefulness of waste banana for generating lactic acid through batch fermentation, using Lactobacillus casei under three treatments. Two treatments consisted of substrates of diluted banana purée, one of which was enriched with salts and amino acids. The control treatment comprised a substrate suitable for L. casei growth. When fermentation was evaluated over time, significant differences (P<0.05) were found in the three treatments for each of five variables analyzed (generation and productivity of lactic acid, and consumption of glucose, fructose, and sucrose). Maximum productivity was (in g l^–1 h^–1) 0.13 for the regular banana treatment, 1.49 for the enriched banana, and 1.48 for the control, with no significant differences found between the latter two treatments. Glucose consumption curves showed that L. casei made greater use of the substrate in the enriched banana and control treatments than in the regular banana treatment. For fructose intake, the enriched banana treatment showed significantly better (P<0.05) results than the regular one. Sucrose consumption was insignificant (P<0.05), probably because fermentation time was too short. Even when enriched, diluted banana purée is an ineffective substrate for L. casei, probably because it lacks nutrients.     

Effect of certain herbicide treatments on pasture composition and inoculum of the take-all fungus

The improvement of pastures by the use of a range of herbicides to eliminate grasses, and their effect on populations of the take-all fungus (Gaeumannomyces graminis vartritici=Ggt) were studied in the field (at Esperance Downs, on the south-coast of Western Australia) from 1982 to 1985. Field trials were conducted to evaluate three herbicide treatments (2,4-D amine+propyzamide; 2,4-D amine+paraquat; paraquat/ diquat) and an unsprayed control. A pot trial involving these treatments with two levels of nitrogen was undertaken to confirm treatment effects observed in the field trial. All herbicide treatments resulted in reduced grass composition of pastures, in both the year of spraying and in the second year of pasture, but reduced dry matter production in the year of spraying. In the year of spraying, however, inoculum ofGgt was reduced (P<0.1) only following the 2,4-D amine+propyzamide treatment and was greater (P<0.1) after 2,4-D amine+paraquat treatment than the unsprayed treatment. Despite reduced grass levels in the herbicide-treated plots in the second year of pasture,Ggt inoculum did not differ between treatments, nor did it after a wheat crop which followed a second year pasture. There was high correlation (P<0.001) between disease levels and dry weights of grasses in the pot trial. There was significantly less (P<0.001) grass in pots treated with herbicides compared to the unsprayed control but no difference (P>0.05) was evident between treatments. Inoculum levels were lower (P<0.05) in the treated pots than the unsprayed control with no evidence of differences among treatments (P>0.05). Nitrogen level had no effect on disease (P>0.05). All herbicide treatments tested reduced grass level and total dry matter, both in the field and in pots. Whereas in the pot trial reduced grass levels resulted in reducedGgt inoculum, in the field such a reduction occurred only with the 2,4-D amine+propyzamide treatment and only in the year of spraying. Herbicide treatments had no effect onGgt inoculum in second year of pasture or crop. Unknown soil and environmental factors in the field precluded a simple relationship between grass level in pasture and subsequent level ofGgt inoculum, and where such a relationship did occur (2,4-D amine+propyzamide treatment) it appeared to be shortlived.     

The effects of copper additives on the quantity and cell viability of adherent Staphylococcus epidermidis in silicone implants

This in vitro study evaluated the antibacterial effect of copper additives in silicone implants. Specimens of a standard silicone material used in breast augmentation and modified copper-loaded silicone specimens were prepared and incubated in a Staphylococcus epidermidis suspension (2 h, 37°C). After the quantification of adhering staphylococci using a biofluorescence assay (Resazurin), the viability of the adhering bacterial cells was quantified by live or dead cell labeling in combination with fluorescence microscopy. In the Resazurin fluorometric quantification, a higher amount of adhering S. epidermidis cells was detected on pure silicone (4612 [2319/7540] relative fluorescence units [rfu]) than on silicone with copper additives (2701 [2158/4153] rfu). Additionally, a significantly higher amount of adhering bacterial cells (5.07% [2.03%/8.93%]) was found for pure silicone than for silicone with copper additives (1.72% [1.26%/2.32%]); (p < 0.001). Calculations from live or dead staining showed that the percentage of dead S. epidermidis cells adhered on pure silicone (52.1%) was significantly lower than on silicone with copper additives (79.7%); (p < 0.001). In vitro, silicone material with copper additives showed antibacterial effects against S. epidermidis. Copper-loaded silicone may prevent bacterial colonization, resulting in lower infection rates of silicone implants.     

Effects of nicotine and vitamin E on glucose 6-phosphate dehydrogenase activity in some rat tissues in vivo and in vitro

Effects of nicotine, and nicotine + vitamin E on glucose 6-phosphate dehydrogenase (G-6PD) activity in rat muscle, heart, lungs, testicle, kidney, stomach, brain and liver were investigated in vivo and in vitro on partially purified homogenates. Supplementation period was 3 weeks (n = 8 rats per group): nicotine [0.5 mg/kg/day, intraperitoneal (ip)]; nicotine + vitamin E [75 mg/kg/day, intragastric (ig)]; and control group (receiving only vehicle). The results showed that nicotine (0.5 mg/kg, ip) inhibited G-6PD activity in the lungs, testicle, kidney, stomach and brain by 12.5% (p < 0.001), 48% (p < 0.001), 20.8% (p < 0.001), 13% (p < 0.001) and 23.35% (p < 0.001) respectively, and nicotine had no effects on the muscle, heart and liver G6PD activity. Also, nicotine + vitamin E inhibited G-6PD activity in the testicle, brain, and liver by 32.5% (p < 0.001), 21.5% (p < 0.001), and 16.5% (p < 0.001) respectively, and nicotine + vitamin E activated the muscle, and stomach G-6PD activity by 36% (p < 0.05), and 20% (p < 0.001) respectively. In addition, nicotine + vitamin E did not have any effects on the heart, lungs, and kidney G-6PD activity. In addition, in vitro studies were also carried out to elucidate the effects of nicotine and vitamin E on G-6PD activity, which correlated well with in vivo experimental results in lungs, testicles, kidney, stomach, brain and liver tissues. These results show that vitamin E administration generally restores the inactivation of G-6PD activity due to nicotine administration in various rat tissues in vivo, and also in vitro.     

Diel observation on the distribution of the sea urchin Strongylocentrotus intermedius under different food availability and shelter conditions in the laboratory

The present study investigated the diel distribution of Strongylocentrotus intermedius in different laboratory food availability and shelter conditions. The diel rhythm of sheltering behaviour was similar between sea urchins in groups 1 (food inside shelter) and 3 (no food available), but significantly different to group 2 (food outside shelter). Among the three treatments, we found significantly more urchins outside shelter in group 2 than in groups 1 and 3 (p?<?0.05), while no significant difference was found between sea urchins in groups 1 and 3 (p?>?0.05). Kruskal–Wallis test confirmed this conclusion. When food was inside shelter, we found significantly more sea urchins staying on food than at other places inside the shelter (p?<?0.001). When food was outside shelter, significantly more individuals chose to stay in shelter rather than on food outside shelter (p?=?0.001). The present study provides new insights into the trade-off of sea urchins between foraging and sheltering behaviours.     

Relative growth rate in relation to physiological and morphological traits for northern hardwood tree seedlings: species,light environment and ontogenetic considerations

The influence of ontogeny, light environment and species on relationships of relative growth rate (RGR) to physiological and morphological traits were examined for first-year northern hardwood tree seedlings. Three Betulaceae species (Betula papyrifera, Betula alleghaniensis and Ostrya virginiana) were grown in high and low light and Quercus rubra and Acer saccharum were grown only in high light. Plant traits were determined at four ages: 41, 62, 83 and 104 days after germination. In high light (610 mol m^–2 s^–1 PPFD), across species and ages, RGR was positively related to the proportion of the plant in leaves (leaf weight ratio, LWR; leaf area ratio, LAR), in situ rates of average canopy net photosynthesis (A) per unit mass (A_mass) and per unit area (A_area), and rates of leaf, stem and root respiration. In low light (127 mol m^–2 s^–1 PPFD), RGR was not correlated with A_mass and A_area whereas RGR was positively correlated with LAR, LWR, and rates of root and stem respiration. RGR was negatively correlated with leaf mass per area in both high and low light. Across light levels, relationships of CO₂ exchange and morphological characteristics with RGR were generally weaker than within light environments. Moreover, relationships were weaker for plant parameters containing a leaf area component (leaf mass per area, LAR and A_area), than those that were solely mass-based (respiration rates, LWR and A_mass). Across light environments, parameters incorporating the proportion of the plant in leaves and rates of photosynthesis explained a greater amount of variation in RGR (e.g. LWR^*A_mass, R²=0.64) than did any single parameter related to whole-plant carbon gain. RGR generally declined with age and mass, which were used as scalars of ontogeny. LWR (and LAR) also declined for seven of the eight species-light treatments and A declined in four of the five species in high light. Decreasing LWR and A with ontogeny may have been partially responsible for decreasing RGR. Declines in RGR were not due to increased respiration resulting from an increase in the proportion of solely respiring tissue (roots and stems). In general, although LWR declined with ontogeny, specific rates of leaf, stem, and root respiration also decreased. The net result was that whole-plant respiration rates per unit leaf mass decreased for all eight treatments. Identifying the major determinants of variation in growth (e.g. LWR^*A_mass) across light environments, species and ontogeny contributes to the establishment of a framework for exploring limits to productivity and the nature of ecological success as measured by growth. The generality of these relationships both across the sources of variation we explored here and across other sources of variation in RGR needs further study.     

Enterocin M and Sage Supplementation in Post-weaning Rabbits: Effects on Growth Performance,Caecal Microbiota,Fermentation and Enzymatic Activity

The effects of enterocin (Ent) M and sage extract applied separately and in combination were investigated. EntM (E 50 μL/animal/day in water) and sage extract (S 10 μL/animal/day in water) were applied individually and in combination (E+S) to rabbits during 21 days of treatment. The rabbits’ growth was not significantly influenced by the additives. Lower feed conversion (FC) was noted in the experimental groups compared with controls, with the lowest data detected in E. The antimicrobial activity of EntM was noted (in E+S: lactic acid bacteria—P < 0.01; in E, E+S: enterococci, enterobacteria—P > 0.05; in E: clostridia—P > 0.05). The most significant changes in fermentation between weaned and older rabbits were noted in amylolytic activity at day 21 (E P < 0.05; E + S P < 0.05); prolonged reduction effect of sage extract on amylolytic activity was observed. The activity of cellulase, pectinase and xylanase was higher in older than in younger animals. Decrease in lactic acid and volatile fatty acids was noted during EntM administration, with significant effect on propionic acid concentration (E P < 0.05; E+S P < 0.001). The sage extract reduced propionic acid (S P < 0.001) and butyric acid levels (S P < 0.05) and increased the concentrations of butyric, iso-valeric, valeric, caproic acids and lactic acid (P < 0.001). It seems to be that EntM and sage supplementation may improve the economy of rabbit farms (increased FC) and the health status of rabbits (reduction of spoilage microbiota, enhanced enzymatic activities in caecum).