Biomass allocation and leaf chemical defence in defoliated seedlings of Quercus serrata with respect to carbon-nitrogen balance

BACKGROUND AND AIMS: Both nutrient availability and defoliation affect the carbon-nutrient balance in plants, which in turn influences biomass allocation (e.g. shoot-to-root ratio) and leaf chemical composition (concentration of nitrogen and secondary compounds). In this study it is questioned whether defoliation alters biomass allocation and chemical defence in a similar fashion to the response to nutrient deficiency. METHODS: Current-year seedlings of Quercus serrata were grown with or without removal of all leaves at three levels of nutrient availability. KEY RESULTS: Plant nitrogen concentration (PNC), a measure of the carbon-nutrient balance in the plant, significantly decreased immediately after defoliation because leaves had higher nitrogen concentrations than stems and roots. However, PNC recovered to levels similar to or higher than that of control plants in 3 or 6 weeks after the defoliation. Nitrogen concentration of leaves produced after defoliation was significantly higher than leaf nitrogen concentration of control leaves. Leaf mass per plant mass (leaf mass ratio, LMR) was positively correlated with PNC but the relationship was significantly different between defoliated and control plants. When compared at the same PNC, defoliated plants had a lower LMR. However, the ratio of the leaf to root tissues that were newly produced after defoliation as a function of PNC did not differ between defoliated and control plants. Defoliated plants had a significantly lower concentration of total phenolics and condensed tannins. Across defoliated and control plants, the leaf tannin concentration was negatively correlated with the leaf nitrogen concentration, suggesting that the amount of carbon-based defensive compounds was controlled by the carbon-nutrient balance at the leaf level. CONCLUSIONS: Defoliation alters biomass allocation and chemical defence through the carbon-nutrient balance at the plant and at the leaf level, respectively.     

Is Method 1664A Silica Gel Treated N-Hexane Extractable Material (SGT-HEM: Non-Polar Materials) a Measure of Total Petroleum Hydrocarbons?

Total Petroleum Hydrocarbons (TPH) is a non-specific parameter defined by EPA Method 418.1. The method is simple, inexpensive and straightforward. Freon 113 is used to extract petroleum from the matrix. The Montreal Protocol precludes the production and importation of Freon 113 into the United States. The search for a cost–effective replacement is underway. US EPA method 1664A Silica Gel Treated N-Hexane Extractable Material (SGT-HEM; Non-Polar Materials) has been considered as a replacement for Method 418.1 by some persons. No comparison data has been provided.

The Tosco Corp. Bayway Refinery has a wastewater discharge permit for Petroleum Hydrocarbons (Oil & Grease) that specifies the use of Method 418.1. The intent of this study was to determine if Method 1664A could replace Method 418.1. Method 418.1 is a direct instrumental measurement of the dried extract. Method 1664A is a gravimetric measurement that requires heating the extract to remove the solvent. Also, a key question to be answered is what carbon range petroleum hydrocarbons does heating the extracts lose? Several evaporation procedures and temperatures were studied.

The study showed that the recovery of petroleum hydrocarbons by method 1664A is temperature dependent and that under the study conditions the method 1664A Silica Gel Treated N-Hexane Extractable Material (SGT-HEM; Non-Polar Materials) can be a replacement for method 418.1.     

Antioxidant and antibacterial capacity of stingless bee honey from Borneo (Sarawak)

Stingless honey bees form a large group of bees that lack of a sting and are found among Meliponinae species indigenous to various tropical and subtropical regions. They are able to produce “stingless bee honey” that contains divergent categories of phenolic and flavonoid compounds and have been associated with antioxidant and antibacterial activity. This study examines the physicochemical properties, antioxidant-activity and anti-microbial activity of stingless bee honey from Malaysia that was produced by Geniotrigona thoracica, Heterotrigona itama and Heterotrigona erythrogastra. The results show that G. thoracica honey has the highest concentration of the total phenolic context (99.04?±?5.14?mg/ml) and the greatest reducing power (19.05?±?0.79%), while flavonoids (17.67?±?0.75?mg/ml), reducing power (18.10?±?0.35%), DPPH (47.40?±?3.18%) and FRAP (50.66?±?5.77?mM of Fe²⁺/100?g) of H. itama honey is significantly higher than those of the other honeys. In addition, G. thoracica honey has the highest antibacterial activity against Staphylococcus xylosus (2.10?±?0.10?cm), which is Gram-positive bacterium, and against Pseudomonas aeruginosa (1.60?±?0.10?cm) and Vibrio parahaemolyticus (2.03?±?0.06?cm), which are Gram-negative bacteria. These results suggest that stingless bee honeys possess useful amounts of phenolic and flavonoid compounds that are able to act as natural anti-oxidants and also have significant anti-microbial activity.     

前外侧肌间隙入路式微创全髋关节置换术对患者髋关节功能及炎性细胞因子水平的影响

目的:探讨前外侧肌间隙入路式微创全髋关节置换术对患者髋关节功能及炎性细胞因子水平的影响。方法:选取2015年1月至2017年1月间在我院行全髋关节置换术的98例患者作为此次研究的研究对象。采用随机数字表法对患者进行分组,其中49例患者作为对照组,行传统全髋关节置换术治疗;49例患者作为观察组,行前外侧肌间隙入路式微创全髋关节置换术治疗。观察并比较两组患者围术期指标,包括切口长度、手术时间、术中失血量、术后1 d引流量。检测并比较两组患者手术前及术后24 h检测血清炎症因子TNF-α、IL-1、IL-6水平。术前及术后3个月和6个月均采用Harris评分评价所有患者髋关节功能。记录并比较两组患者治疗及随访过程中的不良反应发生情况。结果:观察组术中失血量及术后1 d引流量均明显低于对照组,切口长度明显短于对照组,但手术时间明显长于对照组(P0.05)。术后24 h,观察组血清TNF-α、IL-1、IL-6水平明显降低,且明显低于对照组(P0.05)。术后3个月、6个月,两组患者的Harris评分逐渐升高(P0.05),且与同时期的对照组患者比较,观察组患者的Harris评分明显较高(P0.05)。观察组不良反应发生率为8.16%,明显低于对照组的28.57%(P0.05)。结论:前外侧肌间隙入路式微创全髋关节置换术能明显改善患者的围术期指标、降低手术早期的炎性反应,同时能明显促进患者髋关节功能恢复,且安全性良好,值得临床推广。     

Dynamics of intertidal marshes near shallow estuaries in Louisiana

A three-year (1991–1993) field investigation was conducted to quantify the hydrodynamics of intertidal marshes adjacent to tidal channels and shallow bays within two Louisiana coastal regions: (1) the sediment-rich Atchafalaya Basin, and, (2) the sediment-poor Terrebonne Basin with relatively minor riverine inflow. The Terrebonne Basin marsh is regularly inundated and flooding is characterized by sporadic draining interspersed by prolonged flooding events. The maximum water depth on the marsh surface exceeds 50 cm, the flow velocity across marsh surface reaches 10 cm sec^–1, and the sediment deposition rate varies from 10 to 90 g m^–2 per tidal cycle. This rather high sediment deposition rate occurs during winter storms with strong southerly winds. In contrast, the marsh site within the sediment-rich Atchafalaya Basin is irregularly inundated and characterized by sporadic flooding interspersed by prolonged draining. There the marsh flooding depth rarely exceeds 25 cm, the over-marsh flow velocity barely reaches 2.5 cm sec^–1, and the sediment deposition rate ranges from 5 to 50 g m^–2 per tidal cycle. The surprisingly low rate of sediment deposition in a marsh within a sediment-rich region is largely due to the man-made canals that alter the hydrologic regime in the upper reaches of the tidal channel.     

Seasonal variation of phytoplankton community in Thale Sap Songkhla, a lagoonal lake in southern Thailand

The phytoplankton in Thale Sap Songkhla was investigated at 2–3 month intervals from August 1991 to October 1993. The abundance of phytoplankton ranged from 1.4×10⁶ to 1.3×10⁹ cells m^–3. A total of 6 divisions with 103 genera were identified as Bacillariophyta: 49 genera, Chlorophyta: 21 genera, Pyrrhophyta: 15 genera, Cyanophyta: 12 genera, Chrysophyta: 3 genera and Euglenophyta: 3 genera. Although phytoplankton abundance was distinctly greater in the first year of study (August 1991–June 1992) than in the second year (August 1992–October 1993), their patterns are similar: 2 peaks yearly. The peaks of phytoplankton occurred in the heavy rainy season (northeast monsoon) and the light rainy season (southwest monsoon). The main bloom was found during December–January, with a predominance of blue-green algae (e.g. Aphanizomenon andPhormidium) and green algae (e.g. Eudorina). Their species composition also increased, an effect of the large amount of rainfall resulting in low salinity during the northeast monsoon. The minor bloom was produced by diatoms during June–July when water salinity was moderate to seawater. Both phytoplankton numbers and species composition were high. However, unpredictably heavy rainfall during the southwest monsoon period may reduce diatom production due to rapid immediate replacement by blue-green species. Besides salinity concentration, a low total nitrogen: total phosphorus (TN: TP) ratio tended to support the growth of blue-green algae. The diversity of phytoplankton was lowest in the heavy rainy period.     

Feeding rates and productivity of the copepod Acartia bifilosa in a highly turbid estuary; the Gironde (SW France)

Acartia spp. are the dominant copepod species in the Gironde estuary, seaward of the turbidity maximum area. Acartia bifilosa develop a large population in spring and early summer whereas Acartia tonsa appear in late summer. High values and high variability of chlorophyll a/suspended particulate matter ratio are found seaward of the turbidity maximum area. Feeding rates of A. bifilosa were measured by fluorometry. Phytoplankton ingestion was found to be highly variable, between 8 to 80% of copepod carbon body weight. Except for adult females, copepods were heavier in summer than in winter. PB ratios, estimated by the instantaneous growth rate method, varied from 0.03 d^–1 to 0.14 d^–1. The gut contents and P/B ratios of Acartia bifilosa were related to chl a/SPM ratio. From those data, and a few obtained for A. tonsa, it is concluded that only in summer months phytoplankton ingestion is enough to maintain secondary production.     

Degradation of arsenobetaine to inorganic arsenic by bacteria in seawater

The substances suspended in seawater were fractionated by membrane filtration into three fractions. Fraction 1 was collected on a membrane filter of 0.22 µm pore-size, fraction 2 on a 5 µm pore-size and fraction 3 on 0.22 µm pore-size from the filtrate passed through the 5 µm membrane filter. Arsenobetaine was incubated with each of these fractions in two media (ZoBell 2216E and a solution of inorganic salts) at 25 °C in the dark under aerobic conditions. The mixture added with fraction 3 was considered to contain only bacteria. In every case, in the inorganic salt medium, inorganic arsenic(V) was derived from arsenobetaine via trimethylarsine oxide. In the ZoBell medium, arsenobetaine was not degraded to inorganic arsenic, although trimethylarsine oxide was derived in every case. We conclude that the degradation of arsenobetaine to trimethylarsine oxide or inorganic arsenic can be accomplished in seawater by bacteria alone.     

Chemical compositions and physical states of chloroplast lipids related to atrazine resistance in Conyza canadensis L.

A comparison of the chemical composition and physical states of chloroplast lipids, of atrazine-resistant (R) and sensitive (S) biotypes of Conyza canadensis L. (horseweed), in the rosetta stage showed: (1) the R biotype contains lower amounts of polar lipids in its thylakoids, as expressed on a chlorophyll basis, than the S biotype. (2) The chloroplasts of the R biotype have higher contents of monogalactosyl diacylglycerol (MGDG) and lower contents of digalactosyl diacylglycerol (DGDG) and phosphatidylglycerol (PG), than those of the S biotype. (3) The chloroplast total lipids exhibit a higher degree of unsaturation in the R biotype. This is due to a higher level of linolenic acid, and a lower level of palmitic acid in the glycolipids. The fatty acid compositions of the phospholipids, except that of PG, do not differ significantly. (4) The lipid matrix of the thylakoid membranes of the R biotype is more fluid than that of the S biotype, as measured by the fluorescence polarization technique. The results are discussed in terms of whether these differences are responsible for the herbicide resistance.