Effects of thermal acclimation on tissue fatty acid composition of freshwater alewives (Alosa pseudoharengus)

In this study, we examine changes in fatty acid composition of polar and neutral lipids in gill, liver, and muscle of freshwater alewives (Alosa pseudoharengus) after temperature challenges in the laboratory. Alewives experienced either a warm or cold challenge in which temperatures were raised or lowered 0.5°C day⁻¹ over 4–6 weeks. In alewives experiencing the cold challenge, gill polar lipids showed evidence of significant remodeling, including decreases in palmitic acid and saturated fatty acids and increases in n-3 and n-6 highly unsaturated fatty acids including docosahexaenoic acid (DHA) and arachidonic acid. In alewives experiencing the warm challenge, we observed significant increases in saturated fatty acids (due mainly to increased palmitic acid) and decreases in polyunsaturated fatty acids in polar lipids of muscle and liver tissue. Fish that died during the cold challenge had significantly higher levels of palmitic acid in muscle polar lipids compared to fish that survived; fish that died during the warm challenge displayed complex changes in fatty acid composition. Based on theoretical considerations, the changes in polar lipids we observed during thermal acclimation are likely to promote appropriate membrane fluidity under each thermal regime. The increased incorporation of highly unsaturated fatty acids during cold acclimation could have significant physiological and ecological implications. In particular, since highly unsaturated fatty acids are typically scarce in freshwater food webs, dietary deficiencies in these essential fatty acids may be a significant factor in winter mortality of freshwater alewives.     

Redox Stratification and Salinization of Three Kettle Lakes in Southwest Michigan,USA

Redox stratification, especially hypolimnetic anoxia resulting from eutrophication, and salinization resulting from application of salts for road deicing is investigated in three kettle lakes in southwest Michigan. Two of the lakes (Asylum and Woods Lakes) are located in urban Kalamazoo, Michigan, and the third (Brewster Lake) is located in rural Hastings, Michigan. In summer, the water columns of all three lakes are distinctly redox stratified, with anoxic hypolimnia and significant accumulation of reduced solutes (e.g., Mn(II), Fe(II), ammonia) in the lake bottom waters. Extremely elevated conductivity, chloride, sodium, and potassium levels are observed in the urban Asylum and Woods Lakes compared to the rural Brewster Lake, presumably due to runoff of road salt deicers applied in the surrounding watershed. These significant changes in water quality are of concern because they may detrimentally impact lake mixing, biodiversity, and ecosystem function in the urban lakes.     

茶园防霜机不同时间尺度作用效果研究

在发生晚霜的茶园中,试验研究了防霜机不同时间尺度启闭的防霜效果。在茶树萌芽前不同天数、降霜前和日出后不同时间,分别设定开始启用和启闭防霜机的处理,测定其对茶树生长、冠层温度和防霜范围的影响。结果表明：在茶树萌芽前20、15、7 d开始启用防霜机,使新梢长度、芽密度和百芽质量均比对照增加20%以上;防霜机在降霜前2.0、1.5、1.0 h启动,对茶树防霜效果更显著,作用半径比对照增大60%以上;防霜机在日出后2.0、1.5、1.0 h延停,在开始的1 h内可平均减缓冠层温升45.76%,并减小茶树叶片光合强度的降幅。所以,晚霜时为保持茶树较好的长势和产量,应在茶树萌芽前不少于7 d开始启用防霜机,且合适的启动和延停时机分别为降霜前1.0 h和日出后1.0 h。     

Associations Between Dioxins/Furans and Dioxin-Like PCBs in Estuarine Sediment and Blue Crab

The objective of the present study was to evaluate the relationships between the quantity, toxicity, and compositional profile of dioxin/furan compounds (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) in estuarine sediment and in the blue crab (Callinectes sapidus). Sediment and blue crab samples were collected in three small urban estuaries that are in relatively close proximity to each other. Results show that differences between PCDD/F and DL-PCB mass concentrations and total toxic equivalents (TEQ) toxicity in sediments of the three estuaries are reflected in those of the blue crab. TEQs are higher in the hepatopancreas of the crabs than in the sediment, but the concentration factor is inversely proportional to the TEQ in the sediments. Congener profiles in the crabs are systematically different from those in the sediments, and the difference is more pronounced for PCDD/Fs than for DL-PCBs, possibly due to differences in metabolization rates. Compared with sediment profiles, more lesser-chlorinated PCDD/Fs that have higher TEFs accumulate in crab hepatopancreas. This selective bioaccumulation of PCDD/Fs results in a TEQ augmentation in crab hepatopancreas compared with sediments. The bioaccumulation in the blue crab is also selective for PCDD/Fs over DL-PCBs.     

Variable silicon content of rice cultivars grown on everglades histosols 1

Two experiments were conducted to investigate silicon (Si) content in a group of rice cultivars. Ten cultivars were grown in the greenhouse under three levels pf Si fertilization on a Si‐deficient Histosol. In a second experiment, 18 ‘cultivars were grown at three field locations which varied in plant‐available soil Si. In both experiments, cultivars varied in their percentage of Si in rice straw. There was no significant (P > 0.10) genotype by environment interaction. The genotypes with the greatest and lowest percentage of Si were consistently so over all Si environments and treatments.     

Leaf Phosphorus Diagnosis of Sugarcane on Organic Soils

ABSTRACT

Most of the sugarcane (interspecific hybrids of Saccharum sp.) production in Florida is on organic soils. Supplemental phosphorus (P) fertilizer is often applied for optimum yields, but producers are required to reduce P levels in farm drainage waters. The objectives of this study were to relate optimum leaf P tissue concentration with yield in organic soil, and to determine optimum leaf sampling dates during the summer. Eight genotypes were planted at two locations, eight additional genotypes were planted at a third location, and eight more genotypes were planted at a fourth location. Crops were grown for three years. Measurements of leaf P concentration were repeated during growth seasons and over crop years for a total of six sampling dates at each location. Three fertilizer P treatments (0, 24, and 48 kg ha^?1 yr?1) were applied to all genotypes at each location. Leaf samples were partitioned into early-, mid-, and late-summer dates. Early-leaf samples had the widest range in leaf P concentrations compared with mid- and late-season leaf samples. Correlation analyses of yield vs. leaf P concentration across all treatments in early- and mid-summer were statistically significant (P < 0.05), but coefficients were low (r = 0.14 and 0.26, respectively). No consistent relationship across locations described the effect of leaf P tissue concentration on yield. Leaf P concentrations could not provide accurate P fertilization rates that will give maximum sugarcane yields and prevent over-fertilization of P. The highest potential for relating leaf P concentrations with yield appears to be from early leaf samples.     

Identification of 12 EST-derived SSR markers in Lumbricus rubellus

While many species of earthworms are globally distributed, very little is known about the genetic population dynamics of this diverse group. We present the characterization of novel simple sequence repeat (SSR) markers, including primer information, number of alleles, repeat motif, and approximate size ranges, to be used in population genetic analyses of the earthworm Lumbricus rubellus Hoffmeister 1843. Specifically, we designed and characterized 12 novel, polymorphic markers derived from published expressed sequence tags (EST) for amplification in L. rubellus. The mean number of alleles per locus was 6.25 ± 1.91, indicating these markers will be sufficiently polymorphic for population genetic studies of this species.