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The possibility of successful invasion by phytoplankton assemblages in the ballast water of twelve international commercial ships was investigated. Various scenarios of port water dilution rates with a time delay for the exponenti...
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The possibility of successful invasion by phytoplankton assemblages in the ballast water of twelve international commercial ships was investigated. Various scenarios of port water dilution rates with a time delay for the exponential growth of the plankton were considered. Most of the phytoplankton in the ballast water samples originated in countries such as Japan and China, and diatoms dominated (>90% abundance) these phytoplankton communities. To assess their survival after discharge in seawater under various conditions, the phytoplankton were reintroduced into ballast water, pier-side water, and nutrient-enriched f/2 medium and incubated at various water temperatures and salinities for 2 weeks. The growth of the invading phytoplankton was influenced by the time delay for regrowth when introduced in the new seawater conditions. The results also suggest that once introduced by ballast water, the growth of a phytoplankton community may depend more on the nutrient levels and the water temperature and less on the salinity. Although we did not consider parameters such as competition with native species and predation, both high nutrient concentrations and water temperatures may significantly shorten the period before exponential growth occurs, which increases the invasion potential.
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Four lucerne cultivars from Ukraine (Zornitsa, Mne od, Eva-ssp. varia, Raduga-ssp. sativa) and three accessions from Bulgaria (cv. Dara-ssp. sativa, selection number № 2A. № 3AS-ssp. varia) in a field experiment were studied at ...
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Four lucerne cultivars from Ukraine (Zornitsa, Mne od, Eva-ssp. varia, Raduga-ssp. sativa) and three accessions from Bulgaria (cv. Dara-ssp. sativa, selection number № 2A. № 3AS-ssp. varia) in a field experiment were studied at the Institute of Forage Crops. Pleven during 2007-2010.The highest dry matter yield (DMY) was obtained from the Bulgarian variety Dara. The Ukrainian varieties (Zornitsa Mrie od and Eva) originating from ssp. varia had a higher DMY than the variety Raduga (ssp. sativa), but inferior to Dara.The strongest differentiation between subspecies is found for the regrowth rate after harvesting. A representative of ssp sativa is a statistically proven faster regrowth rate and greater length of the stemsCharacterization performed shows that selection number № 2A features a light purple color (subclass 13 E), high dense sward and good regrowth rate. For № 3AS was found to be medium dark purple color (subclass 1.2 D), high dry matter yield, good dense sward, very good rate of regrowth.Both numbers confirm basic characteristics of the level of progeny, such as stems crawling on the soil surface during the late autumn, high stem density and rapid regrowth rate. Suitable in the field of alfalfa pasture use.
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Clonally propagated crop collections such as yams (Dioscorea spp.), and cassava (Manihot esculenta Crantz) are maintained at the Genetic Resources Centre of the International Institute of Tropical Agriculture (IITA). However, clon...
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Clonally propagated crop collections such as yams (Dioscorea spp.), and cassava (Manihot esculenta Crantz) are maintained at the Genetic Resources Centre of the International Institute of Tropical Agriculture (IITA). However, clonal diversity is at risk of loss because of several negative factors such as adverse environmental conditions, pests, diseases, and genetic contaminations of field material, or plant ageing, data handling errors, pathogen contaminations, and higher epigenetic variations in material conserved in vitro. Using liquid nitrogen at -196°C, cryopreservation is the most reliable and cost-effective conservation means for the long-term safeguarding of clonal crop collections. It also allows effective and standard germplasm safety duplication. Cryopreservation requires, among other criteria, an optimal protocol and reliable procedure that can ensure high standards and consistent plantlets recovery, on which the efficiency of any cryopreservation project is evaluated. This study aimsto optimise cryopreservation parameters for cassava and yam meristem cryobanking. Experiments on selected cassava and yam accessions were carried out to improve meristem regrowth rate via culture media optimisation using antioxidants (lipoic acid, ascorbic acid and glutathione). Also, cryogenic methods (droplet vitrification and V cryo-plate) were evaluated to determine the most efficient one for optimal meristem regrowth rate. This study showed the favourable effect of antioxidants, incorporated in thepre-culture and meristem regrowth culture media, on cryopreserved yam meristem regrowth. It was also observed that the V cryo-plate cryogenic method allowed a better cassava meristem regrowth rate. These results led to optimised protocols and were the basis of a 4-steps procedure for cassava and yam collections cryobanking at IITA since 2017. The implementation of cassava and yam cryobanking is integrated into the institute's global clonal crop conservation strategy for sustainable use in more resilient and productive agriculture.
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Carbohydrate and N reserves are important for perennial grass regrowth after defoliation. The objective of this study was to quantify the effects of N fertilization on dynamics of reserve accumulation and utilization for regrowth ...
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Carbohydrate and N reserves are important for perennial grass regrowth after defoliation. The objective of this study was to quantify the effects of N fertilization on dynamics of reserve accumulation and utilization for regrowth of a C-4 perennial grass. A field study was conducted at Gainesville, FL, on established 'Tifton 85' bermudagrass (Cynodon spp.) in 2006 and 2007. Treatments were N rates of 0, 45, 90, and 135 kg N ha(-1) regrowth period(-1). Total nonstructural carbohydrate (TNC) and N concentrations, leaf area index (LAI), and canopy carbon exchange rate (CER) were measured weekly during 28-d regrowth periods. Stem and rhizome TNC concentrations decreased with increasing N rate, ranging from 20 to 80 mg g(-1) for stem and 45 to 145 mg g(-1) for rhizome, and followed quadratic time trends, with minima between 7 and 14 d of regrowth, suggesting reserve utilization up to 2 wk after defoliation. Leaf, stem, rhizome, and root N concentrations increased with N rate. Leaf and stem N concentrations followed quadratic time trends, with maxima between 7 and 14 d of regrowth, and ranged from 15 to 50 mg g(-1) for leaf and 10 to 40 mg g(-1) for stem. Rhizome N concentrations were constant throughout regrowth. Canopy CER and LAI followed logistic time trends within each 28-d regrowth period, with upper asymptotes raised by increased N rate. Nitrogen fertilization increased TNC reserve utilization, LAI, and canopy CER, thereby increasing shoot regrowth at rates up to 90 kg N ha(-1) period(-1).
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The high concentration of crude protein in the forage is one of the primary requirements for alfalfa varieties A best balance between quantity and quality in forage crops is the most important target of the breeding research, sinc...
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The high concentration of crude protein in the forage is one of the primary requirements for alfalfa varieties A best balance between quantity and quality in forage crops is the most important target of the breeding research, since these traits are generally inversely correlated.The experiment was carried out during 2009 to 2012 at the Experimental field of Institute of Agriculture and Seed Science 'Obraztsov chiflik' - Rousse. Seven synthetic population and Prista 2 variety - standart were included. .The objective of this studywas to determine crude protein content in dry matter of new germplasm and using th4 methods of correlative and regressive analysis to evaluate its relationship with some agronomic traits - dry matter yield, grass stand height and regrowth rate after cutting.The synthetic population SP_(05)-26 was characterized with the highest protein content in dry matter (19.46%). The strongest complex interaction (R=0.82) of the studied traits on the crude proteira content in the second year of alfalfa growing was found The data indicate that there was strong negative correlation between crude protein content and both grass stand height and regrowth rate after cutting (r=-0.80) and 收起
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Perennial grain has been proposed to provide an effective means of ensuring both food and ecological security. The newly released cultivar of perennial rice 23 (PR23) represents a new rice production system that is based on no-til...
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Perennial grain has been proposed to provide an effective means of ensuring both food and ecological security. The newly released cultivar of perennial rice 23 (PR23) represents a new rice production system that is based on no-tillage. Nevertheless, how perennial rice responds to this new system remains unclear. Two field experiments were conducted over four successive seasons from 2016 to 2017 in Jinghong, Yunnan Province, Southern China. Field experiment 1 showed perennial rice is an economically viable and environmentally safe cropping system compared to annual rice, and could obtain a stable and sustainable grain yield economically for successive seasons across years. In the perennial rice cropping system, N fertilizer had some negative effects on the regrowth of perennial rice. Field experiment 2 with four N rates N0, N1, N2 and N3 with 0, 120, 180 and 240 kg N ha(-1), respectively and three planting densities D1, D2 and D3 with 10, 16.7 and 22.6 plants m(-2), respectively on perennial rice was conducted to assess and ameliorate these negative effects of N fertilizer on the regrowth of perennial rice. The results showed that: (1) the N2D3 treatment (180 kg N ha(-1) integrated with 22.6 plants m(-2)) resulted in a stable and high grain yield across three successive regrowth seasons (6.93 t ha(-1)) and optimized yield components (panicle no. m(-2), spikelet no. panicle(-1), grain weight) and root activity (10.81 g h(-1) m(-2)); (2) the regrowth of perennial rice 23 was significantly limited by N fertilizer (P<0.05), and the N0D2 treatment had the best regrowth ability (97.8 %) across the three regrowth seasons; (3) additionally, the N2D3 treatment had the best N net productivity (27 kg N kg(-1)), profit (79 CNY kg(-1)) and sustainable production capacity (0.59), and could obtain more economic profit in successive perennial rice production. Perennial rice was able to be sustainably and economically produced for successive regrowth seasons across years, and the N2D3 treatment provided optimal conditions, which enhanced the regrowth rate, N productivity, economic benefit and yield potential. The use of less chemical N fertilizer and a higher planting density could enhance the sustainability of the grain yield and reduce fertilizer loss via a novel crop management scheme for perennial rice.
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Twigs of Salix species are candidates for cryopreservation procedures because they become tolerant of freezing temperatures during mid-winter. We examined several variables in developing a two-step cryopreservation procedure for s...
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Twigs of Salix species are candidates for cryopreservation procedures because they become tolerant of freezing temperatures during mid-winter. We examined several variables in developing a two-step cryopreservation procedure for sections from these twigs. Samples of Salix triandra cooled to -30degreesC or -35degreesC and then transferred to the vapor phase over liquid nitrogen gave the greatest percent shoot formation. Cooling rate to -35degreesC had a major influence on shoot formation. Samples cooled at rates greater than 10degreesC/hr showed no shoot formation. The highest percent of shoot formation was achieved by cooling at 0.21degreesC/hr. Cooling rate from -35degreesC to liquid nitrogen did not influence shoot formation. Warming procedures affected shoot formation. Transferring samples from -160degreesC either to a +2degreesC cold room or to -3degreesC methanol gave similar levels of shoot formation. No shoot formation occurred either with warming in +40degreesC water or very slowly in a Styrofoam box. Eight of eleven Salix taxa tested using the established protocol had significant levels of shoot formation after cryogenic treatment. [References: 14]
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Ozonation of the return activated sludge (AS) flow is an emerging option for excess-sludge reduction. This study aimed to evaluate the potential changes suffered by some kinetic parameters of the activated sludge models (ASMs) in ...
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Ozonation of the return activated sludge (AS) flow is an emerging option for excess-sludge reduction. This study aimed to evaluate the potential changes suffered by some kinetic parameters of the activated sludge models (ASMs) in the combined ozone-AS process. The heterotrophic maximum specific growth rate (mu(Hmax)) was determined by respirometry in three model-sludges (S1 to S3) treated in batch with different O-3 doses. S1 was a fresh synthetic biosolid composed by only two particulate fractions. S2 was a digestate of S1 almost made by the endogenous residues. S3 was from a municipal wastewater treatment plant. mu(Hmax) increased significantly from 3.5 d(-1) originally, to more than 10 d(-1) in the ozonated sludges. Ozonation promoted the selection of fast-growing bacteria in the activated sludges, after transitory inactivation and long lag times. Some microorganisms survived to 3 months of digestion and subsequent ozonation, and then regrow faster than before, once fed again with acetate. The research is of interest from the point of view of the application of the ASM models to the ozone-AS process, but also for wastewater disinfection in general. (C) 2017 Elsevier Ltd. All rights reserved.
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