Nursery performance of Pacific white shrimp (Litopenaeus vannamei Boone, 1931) cultivated in a biofloc system: the effect of adding different carbon sources

Effect of different carbon sources on nursery performance of Pacific white shrimp (Litopenaeus vannamei) cultivated in biofloc system was investigated. Shrimp postlarvae (98.47 ± 8.6 mg) were fed for 32 days in tanks with water volume of 130 L and density of 1 individual L^?1. One control treatment and four biofloc treatments (BFT1, BFT2, BFT3 and BFT4) with adding different carbon sources including molasses, starch, wheat flour and mixture of them, respectively, were considered at equal weight ratios. According to the results, salinity, dissolved oxygen and pH were not significantly different among the biofloc treatments (P > 0.05). Maximum pH (8.27) and maximum dissolved oxygen (6.35 mg L^?1) were recorded in the control. Maximum (0.43 mg L^?1) and minimum (0.09 mg L^?1) ammonia were recorded in the control and BFT2, respectively (P < 0.05). Using simple carbohydrates (molasses and starch) lowered the ammonia concentration significantly. The highest increase in body weight (1640.43 ± 231.28 mg), growth rate, specific growth rate (8.97 ± 0.42% per day) and biomass (190.29 ± 26.83 mg) were found in BFT1 and the highest survival (90 ± 0.77%) was found in BFT4. The highest feed conversion (1.52 ± 0.23) and the lowest feed efficiency (66.81 ± 7.95) were observed in the control (P < 0.05). The proximate composition analysis revealed an increase in lipid and ash in biofloc treatments. Results indicated that using biofloc technology with zero‐water exchange system and adding carbon sources could help to recycle waste and improve the water quality. Moreover, the type of carbonaceous organic matter as a substrate for heterotrophic bacteria would be effective in degradation and metabolization of ammonia and nitrite.     

Genotype-Dependent Differential Responses of Three Forage Species to Calcium Supplement in Saline Conditions

Salt toxicity comprises of osmotic and ionic components both of which can severely affect root and shoot growth. In many crop species, supplemental calcium (Ca) reduces the inhibition of growth typical of exposure to salt stress. The objective of this study was to compare whole plant growth and physiological responses to interactive effect of salinity and Ca level on three forage species [African millet (AM), tall wheat grass (TW), and perennial ryegrass (PR)] differing in tolerance to sodium chloride (NaCl) salinity. Plants were grown under glasshouse condition and supplied with nutrient solution containing 0, 100, and 250 mM NaCl supplemented with 0.5, 5, or 10 mM calcium chloride (CaCl₂). Plant growth, ionic concentration, water relations, and solute (proline and glycinebetaine) concentrations of the plants were determined two weeks after the salinity treatments. At 100 mM NaCl, there was a moderate reduction in dry matter (DM) production of all three species. A drastic decrease in DM occurred at 250 mM NaCl. Supplemental Ca reduced the adverse effects of salinity on all three species. The TW showed higher shoot and root growth in 100 and 250 mM NaCl than AM and PR. It also showed the highest DM at 5 and 10 mM Ca supplement. The shoot and root DM of TW increased by about 45 and 15%, respectively compared to the control. Chemical analysis indicated that in TW, Ca restricted both uptake and transport of sodium (Na) from root to shoot. It also increased Ca and potassium (K) concentrations in both organs. The transport of K and Ca from root to shoot of AM and PR were decreased by NaCl, but were restored with increasing Ca in the medium. The opposite occurred for Na. In PR, more K uptake was observed in shoot at 250 mM NaCl with 10 mM Ca supplement. The sap osmotic potential (Ψ_S) was the highest in TW at 10 mM Ca in the presence of 250 mM NaCl. Contribution of various solutes to the difference in Ψ_S among the species from the control and 250 mM salt treatment differed greatly. Supplemental Ca induced decline in the leaf Ψ_S of TW which was predominately due to K, glycinebetaine, Na and proline accumulation. Addition of 10 mM Ca to the growth medium maintained a low Na and a high K level. Accumulation of glycinebetaine and proline in leaf contributed the NaCl tolerance of TW. The presented results suggest that supplement Ca, not only improved ionic relations but also induced plant ability in production of compatible solutes (glycinebetaine and proline) and osmotic adjustment. Accordingly, genotype dependent capacity could be found using supplemental Ca.     

Elucidate Genetic Diversity and Population Structure of Bread Wheat (Triticum Aestivum L.) Cultivars Using IRAP and REMAP Markers

Journal of Crop Science and Biotechnology - Analysis of genetic diversity and population structure in bread wheat is an essential step in their conservation, utilization, and breeding....     

Effects of dietary fish oil substitution with mixed vegetable oils on growth and fillet fatty acid composition of juvenile Caspian great sturgeon (Huso huso)

The objective of this study was to determine the effects of fish oil replacement with dietary vegetable oils on growth performance, chemical composition and fatty acids profiles in fillets of farmed Caspian great sturgeon juveniles Huso huso (26.97 ± 0.49 g). Five isonitrogenous and isolipidic diets were formulated, containing 10 % of added oil. The diet with 100 % kilka fish oil (Caspian tyulka, Clupeonella caspia) was the control. Fish oil was substituted by 50 % of vegetable oils consisting of an equal share of sunflower and soybean oils (diet A), sunflower and canola oils (diet B) and soybean and canola oils (diet C). In diet D, 100 % of fish oil was replaced with vegetable oil (1:1:1 ratio of sunflower oil, soybean oil and canola oil). Significant differences (P > 0.05) were not detected during 60 days feeding trial in final body weight, weight gain, condition factor, specific growth rate, feed conversion rate, protein efficiency ratio and the chemical composition of fillet (crude protein, crude lipid, moisture and ash). Generally, the fatty acids composition of fish fillets was reflective of the dietary lipid sources. These results indicate the feasibility of substituting fish oils with the mixture of vegetable oils in diets of juvenile H. huso without negative influence on growth providing optimum ratios of n-3/n-6 and n-3/18:1n-9 is met in the diet.     

Compensatory growth,plasma hormones and metabolites in juvenile Siberian sturgeon (Acipenser baerii,Brandt 1869) subjected to fasting and re‐feeding

A 7‐week study was conducted to investigate the effect of different fasting and re‐feeding regimes on compensatory growth and some physiological parameters of juvenile Siberian sturgeon (Acipenser baerii). Fish (46.5 ± 0.5 g) were fed on a diet (containing 450 g/kg crude protein and 20 MJ/kg digestible energy) according to four feeding regimes in triplicate including: control group (C, fed everyday), W1 (2 weeks of feeding followed by 1 week of fasting and 4 weeks of re‐feeding), W2 (1 week of feeding followed by 2 weeks of fasting and 4 weeks of re‐feeding) and W3 (3 weeks of fasting followed by 4 weeks of re‐feeding). The fasted groups including W1 (119.6 ± 2.1 g), W2 (118.0 ± 1.7 g) and W3 (108.5 ± 4.8) significantly lost their weights during fasting phase and did not attain the final weight of the C (137.3 ± 1.7 g) after re‐feeding phase. The re‐feeding phase increased the specific growth rate in the fasted groups compared to the C (p < .05). After the fasting phase, concentrations of T₃, T₄, glucose, total protein and triglyceride in plasma of fasted groups were decreased, but levels of total cholesterol, aspartate aminotransferase, alkaline phosphatase and lactate dehydrogenase increased compared to the C. After re‐feeding phase, except for glucose level, all mentioned metabolites were restored in the plasma of W1 group, but total protein level and aspartate aminotransferase concentrations in plasma were not restored in W2 and W3 groups. Overall, our finding demonstrated 4 weeks of re‐feeding was too short to induce full compensatory growth in A. baerii juveniles.     

Metallothionein biosynthesis as a detoxification mechanism in mercury exposure in fish,spotted scat (<Emphasis Type="Italic">Scatophagus argus</Emphasis>)

It is of crucial importance to study on the biomarkers types to assess the specification of the pollutants and health status of marine ecosystems in environmental evaluation projects. In this respect, total metallothionein biosynthesis and mercury bioaccumulation in the liver and gills under acute mercury exposure were investigated in fish, Scat (Scatophagus argus). Spotted scat was exposed to different mercury concentrations (0, 10, 20, 30) for 24, 48, 72 h. Total MT levels were determined by enzyme-linked immunosorbent assay (ELISA) method. Mercury contents were determined through cold vapor atomic absorption spectrometry (CVAAS). Induction of MT during exposure was tissue specific, displaying different response pattern in gills and liver. Mercury accumulated in liver much higher than in gills and the latter also showed lower MT level (P < 0.05). MT biosynthesis in liver showed a significant (P < 0.05) increase after exposure to different mercury concentration with increase in exposure time, whereas total MT content did not significantly (P > 0.05) change in gills except for 72 h exposure at 30 μg l⁻¹. Nonetheless, the relationship between MT biosynthesis and Mercury bioaccumulation in both tissues was significant (P < 0.05). The results suggest that this form of MT in S. argus was Hg inducible and could be extended as a biomarker of mercury pollution in marine ecosystems.     

Perspective: root exudation of herbicides as a novel mode of herbicide resistance in weeds

The evolution of resistance to herbicides in weeds has become a great challenge for global agricultural production. Weeds have evolved resistance to herbicides through many different physiological mechanisms. Some weed species are known to secrete herbicide molecules from roots into the rhizosphere upon being treated. However, root exudation of herbicides as a mechanism of resistance has only recently been identified in two weed species. Root exudation pathways have been investigated in Arabidopsis, and this work suggested that ATP‐binding cassette (ABC) and multidrug and toxic compound extrusion (MATE) transporters play a role in the secretion of primary and secondary plant products from roots. We hypothesize that the mechanisms involved in root exudation of herbicides that result in resistance are mediated by overactive or overexpressed transporters, probably similar to those found for the exudation of primary and secondary compounds from roots. Elucidating the molecular and physiological basis of root exudation in herbicide‐resistant weeds would improve our understanding of the pathways involved in herbicide root secretion mediated by transporters in plants. © 2020 Society of Chemical Industry     

Effects of soil tillage,canola (Brassica napus L.) cultivars and planting date on canola yield,and oil and some biological and physical properties of soil

Determination of different agronomical properties including soil-related parameters for enhanced canola (Brassica napus L.) production can be of great significance. Hence, the objectives were to determine the effects of different tillage systems, canola cultivars and different planting dates on: (i) canola yield and oil, and (ii) soil moisture and microbial carbon (C) and nitrogen (N). Two field experiments were planned as split-plot experiments in three replicates. The main plots were different tillage systems including no-tillage (NT), minimum tillage (MT) and conventional tillage (CT), and the subplots were the combination of different canola cultivars (PF and Hyola 401) and different planting dates (PD): 8 and 23 September and 7 October. Soil moisture under CT and PF was significantly less than that of MT and NT, and Hyola 401, respectively. Carbon and N microbial biomass was the highest at NT and on the first PD. The tillage method and planting date also significantly affected canola yield, oil content and the amount, and the number of earthworms. We may conclude that although the amount of yield was the highest at CT, it may be more agronomically sustainable to plant canola under NT or MT earlier during the autumn growing season.     

Kinetic Study of BTEX Removal Using Granulated Surfactant-Modified Natural Zeolites Nanoparticles

Increasing release of organic pollutants to the environment has caused one of the largest world crises for water resources. Volatile organic compounds are toxic monoaromatic pollutants of soil and water. In this research, natural zeolite nanoparticles were produced mechanically by means of a milling technique, modified using two cationic surfactants of hexadecyltrimethylammonium chloride and n-cetyl pyridinium bromide and formed as granules using a novel technique already developed by our group. The granulated adsorbents were used to uptake benzene, toluene, ethylbenzene, and xylenes (BTEX) from contaminated water. Two intra-particle diffusion models (i.e., Weber and Morris and Vermeulen models) and three surface reaction models (i.e., pseudo-first order, pseudo-second order, and Elovich) were applied to evaluate the kinetics of adsorption and the best fitted model was chosen. Results of the adsorption kinetic evaluations were shown that uptake of granulated nanozeolites are higher than natural zeolites (in the order of four). Kinetic results revealed that the adsorption follows a pseudo-second order indicating existence of chemisorption in the studied conditions. It was noticed that the intra-particle diffusion is prevailing in the first stage of adsorption for a relatively short time (i.e., first 25 min).