Accompanying ions of ammonium sources and nitrate : ammonium ratios in tomato plants

The tomato (Solanum lycopersicum L.) cultivar Micro‐Tom (MT) is widely used in physiological studies, but the effects of nitrate ( ) and ammonium ( ) ratios ( : ratios) and, in particular, the effects of the accompanying ions in sources are unknown. To determine whether the accompanying ions in sources influence toxicity, the effects of : ratios on the physiology, electrolyte leakage index, nutrition, and dry weight were studied using hydroponics. The sources were ammonium chloride (NH₄Cl) or ammonium sulfate [(NH₄)₂SO₄], and five : ratios were used: 100 : 0, 75 : 25, 50 : 50, 25 : 75, and 0 : 100. The source was calcium nitrate [Ca(NO₃)₂], and the nitrogen (N) concentration was 15 mmol L^?1. The results indicate that NH₄Cl or (NH₄)₂SO₄ can be used in studies on toxicity because the accompanying ions did not influence the tomato plants. In addition, : ratios of 100 : 0 and 75 : 25 resulted in the highest dry weight of tomato plants, whereas ratios of 25 : 75 or 0 : 100 were toxic.     

Breeding systems in Coix lacryma-jobi populations

Summary Six populations of Coix lacryma-jobi with distinct characters were studied to evaluate the presence of autonomous apomixis and pseudogamy, and to determine its implications and effects in the calculations of the rate of breeding. For this reason, two types of genetic markers were used-morphological markers and isozymatic markers.The results show that autonomous apomixis does not seem to occur in these populations. Further experiments are necessary to prove the presence of pseudogamy in one of the populations. The rate of natural outcrossing in the grain types Rosario, Rosadlay and I-47 fluctuated around 35.9% using estimates based on isozymatic markers. The rate of natural outcrossing was 37.4% in the Adlay population using morphological markers. A population composed of tall individuals, named Tailândia, which has a greater vegetative mass and fewer grains, presented a high level of natural outcrossing at 72.8%. This information is important for many reasons, such as: 1) guiding sampling strategies of genetic material, 2) in the organization and upkeep of germplasm banks, and 3) for plant breeding programs.     

Assessing the use of erosion modeling to support payment for environmental services programs

Purpose

Payment for environmental services (PES) has assumed increasing importance in discussions about sustainable development strategies. Many of the PES programs are based on water erosion control and the corresponding environmental and economic benefits generated in the basins where they are implemented. The main objective of this study was to show how erosion susceptibility models can support PES programs.

Materials and methods

The application of the Universal Soil Loss Equation (USLE) in the Sarandi Experimental River Basin (32.7 km²), located in the Federal District, Brazil, was used as a study case. Then a scheme for organizing knowledge about ecosystem services related to erosion control and water resources was performed. Considering the generated scheme, the USLE results, the land use map, and the water use in the region, we evaluated how erosion modeling could support PES programs.

Results and discussion

The results show that a large part of the study basin (90%) presents “low” susceptibility to erosion, which is significant in terms of the use and conservation of ecosystem services, as well as being a limitation regarding the need for the implantation of PES programs for erosion control. Incentives for maintaining the natural vegetation in areas with higher erosion susceptibility have the greatest potential to justify PES programs in the study basin, and the sanitation company is the potential payer for erosion control in the Sarandi River Basin.

Conclusions

The application of the USLE in a spatially distributed form proved to be an important support tool for land management and the implementation of PES policies.     

Growth of juvenile common snook (Centropomus undecimalis Bloch, 1792) reared at different temperatures and salinities: Morphometric parameters,RNA/DNA,and protein/DNA ratios

We investigated the growth of juvenile common snook (Centropomus undecimalis) reared at 25°C and 28°C and salinities of 0.3, 15, and 32 g L^?1. Total length, weight, RNA/DNA, and protein/DNA ratios were determined after 90 days of experiment. Higher growth was observed at 28ºC compared with 25°C, at the same salinity. At 28°C and 15 g L^?1 salinity, the weight (25.14 g) of juveniles was twice that of the juveniles reared at the lower temperature. At different salinities, only higher temperature affected growth, with higher weight values obtained at 15 g L^?1 in comparison with 0.3 and 32 g L^?1. Length was similar at 0.3 and 15 g L^?1. The RNA/DNA ratio was greater in juveniles reared at a salinity of 15 g L^?1 when compared with 0.3 and 32 g L^?1. This study shows that the combination of higher temperature and intermediate salinity promotes better growth of common snook juveniles.     

Introduction of jundia Rhamdia quelen (Quoy & Gaimard) and Nile tilapia Oreochromis niloticus (Linnaeus) increases the productivity of carp polyculture in southern Brazil

Fish polyculture is based on the assumption that each species has its own feeding niche and may increase the maximum standing crop of a pond by exploring a wider range of available food and ecological niches. In order to identify the better species ratio and to introduce jundia (JN) (Rhamdia quelen Quoy & Gaimard) and Nile tilapia (NT) (Oreochromis niloticus Linnaeus) in to the carp polyculture practiced in South Brazil, a 162‐day experiment was conducted, in 12 250‐m² earthen ponds (1.2 m deep). Treatment I (T‐I) contained 35% common carp, Cyprinus carpio (L.) (CC); 35% grass carp, Ctenopharyngodon idella Valenciennes (GC); 15% silver carp, Hypophthalmichthys molitrix Valenciennes (SC); and 15% bighead carp, Aristichthys nobilis Richardson (BC). Treatment II (T‐II) consisted of three ponds stocked at the following ratio: 17.5% CC, 35% GC, 15% SC, 15% BC and 17.5% JN. Treatment III (T‐III) consisted of three ponds with 35% CC, 35% GC, 7.5% SC, 7.5% BC and 15% NT. Treatment IV (T‐IV) consisted of three ponds with 17.5% CC, 35% GC, 7.5% SC, 7.5% BC%, 17.5% JN and 15% NT. No significant correlation was found between the treatments with different species ratio and water quality parameters. The final weight of different species, in different treatments, was statistically different. The major result was the clear positive effect on growth parameters observed by the introduction of JN and/or NT in to the carp polyculture. The yield per hectare was 2083.33±183 kg ha^?1 for polyculture with carp species; 2476.67±139.88 kg ha^?1 following the introduction of JN only; 2801.67±111.42 kg ha^?1 for isolated introduction of NT; and 2506.67±422.31 kg ha^?1 for simultaneous introduction of JN and NT. The introduction of JN and/or NT had a positive effect on growth parameters when compared with carp‐only polyculture. The reduction in CC ratio also had a positive effect on growth parameters.     

Two epizootic Perkinsus spp. events in commercial oyster farms at Santa Catarina,Brazil

Perkinsus spp. have been detected in various bivalve species from north‐east Brazil. Santa Catarina is a South Brasil state with the highest national oyster production. Considering the pathogenicity of some Perkinsus spp., a study was carried out to survey perkinsosis in two oyster species cultured in this State, the mangrove oyster Crassostrea gasar and the Pacific oyster Crassostrea gigas. Sampling involved eight sites along the state coast, and oyster sampling was collected during the period between January 2013 and December 2014. For the detection of Perkinsus, Ray's fluid thioglycollate medium (RFTM) and histology were used, and for the identification of the species, PCR and DNA sequencing were used. Perkinsus spp. was found by RFTM in C. gigas and C. gasar from São Francisco do Sul. This pathology was also detected in C. gasar from Balneário Barra do Sul both, by RFTM and histology. Perkinsus marinus was identified in C. gigas and C. gasar from São Francisco do Sul and Perkinsus beihaiensis in C. gasar from Balneário Barra do Sul. This is the first report of P. marinus in C. gigas from South America. Results of this preliminary study suggest that both oyster species tolerate the species of Perkinsus identified, without suffering heavy lesions.