The cause of death of juvenile Pacific bluefin tuna (Thunnus orientalis) reared in sea net cages

Although the survival rate of juvenile Pacific bluefin tuna Thunnus orientalis (PBT) during 30 days after stocking in sea net cages has been as low as approximately 50%, the reason for this high mortality is not clear. The dead fish were collected and counted during 30 days after stocking in a sea net cage, and the growth performance, stomach contents, and bone injury were investigated. Nearly half (47.9%) had died within the first 4 days. The total length and body weight of the dead fish were significantly smaller than those of the live fish, and the weight of the dead fish did not increase during the first 7 days. Approximately one-third of the dead fish (21.9–42.9% per day) had ingested inorganic matter such as wood or Styrofoam waste during the first 7 days, and 25.0–45.0% of the dead fish sampled per day showed poor growth. The daily ingestion rate of inorganic matter decreased dramatically from the eighth day, when the daily mortality rate decreased. The percentage of dead fish with bone injuries due to collision or contact was low (less than 15%). These results suggest that one of the causes of high mortality during several days after stocking in a sea cage was accidental ingestion of inorganic matter by juvenile PBT. Improvement in feeding method can increase the survival rate of juveniles in sea net cages.     

Weed control with pre-emergence herbicides in vegetable soybean (Glycine max L. Merrill)

Field and laboratory experiments were conducted in the early and late rainy seasons in Thailand to evaluate the effect of pre-emergence application of herbicides and determine the herbicide residues on vegetable soybean (Glycine max L. Merrill cv. No. 75) production. No visible crop injury was observed after application of alachlor 469 g a.i./ha, clomazone 1080 g a.i./ha, metribuzin 525 g a.i./ha, pendimethalin 1031.25 g a.i./ha, tank-mixed clomazone 960 g a.i./ha + pendimethalin 928 g a.i./ha, or tank-mixed metribuzin 350 g a.i./ha + pendimethalin 928 g a.i./ha. However, acetochlor 1875 g a.i./ha, isoxaflutole 75 g a.i./ha, and oxadiazon 1000 g a.i./ha caused visible crop injury. Plant bioassay of herbicide residues in the soil after harvest showed no phytotoxic effect on baby corn (Zea mays Linn. cv. Suwan 3), cucumber (Cucumis sativus L. cv. Pijit 1), pak choi (Brassica chinensis Jusl. cv. Chinensis), and soybean (G. max L. Merrill cv. CM 60). Gas Chromatography-Mass Spectrometry (GC–MS) analysis showed no significant herbicide residues on crop yield (or MRLs < 0.01 ppm) for all herbicides used in this study. The application of metribuzin at 525 g a.i./ha was sufficient to provide satisfactory full-season control of several weed species and gave the highest crop yield. In addition, pendimethalin at 1031.25 g a.i./ha, and tank-mixed metribuzin at 350 g a.i./ha + pendimethalin at 928 g a.i./ha can provide a similar level of weed control as an alternative to reduce herbicide dosage thereby increasing food and environmental safety in vegetable soybean production.     

发生氢化物－原子吸收光谱法测定树叶中痕量砷的研究

该文研究的用ＫＩ－ＶＣ预还原ＨＡＡＳ直接测定树叶中痕量砷的分析方法，测定工厂多种树叶中砷的含量，并同时与无污染区同类树种进行对比．这对于工厂正确选择抗污染绿化树种，净化空气，美化环境提供了科学依据．     

Distribution of solanesol in Nicotiana tabacum

Solanesol is an important secondary metabolite in Nicotiana tabacum. Distribution of solanesol in Nicotiana tabacum was investigated by High Performance Liquid Chromatography （HPLC） method. The quantitative distribution of solanesol in various organs and tissues of N. tabacum showed that solanesol content, obviously different in all organs, was 6.8, 18.3, 27.5, 45.8, and 68.0 times higher in leaves than that in the stalks, flowers, seeds, fruits and roots, respectively. The contents of solanesol in various parts of leaf, stalk and flower were determined. The content of solanesol in top leaf, middle leaf and bottom leaf gradually decreased （6.124, 5.813 and 5.687 mg.g^-1, respectively） and the content of solanesol in various leaf-parts （leaf apex, leaf middle and leaf base） also gradually decreased. The content of solanesol in top stalk was 1.19 times and 1.92 times higher than that in the middle stalk and the bottom stalk, respectively. The content of solanesol in various tissues of stalk （epidermis, cortex and stele） dramatically decreased. The sepal contained higher concentration of solanesol （1.192 mg·g^-1） compared to any other parts in flower. The study will provide the base data for the regulation and control of solanesol, moreover, it will provide the scientific evidences for the rational development and utilization of N. tabacum resources.     

火焰原子吸收光谱法测定黄花菜中微量元素含量

[目的]测定黄花菜中微量元素的含量。[方法]采用火焰原子吸收光谱法对黄花菜中7种金属元素(K、Ca、Mg、Zn、Fe、Cu、Mn)含量进行测定。[结果]黄花菜中K、Ca、Mg、Zn、Fe、Cu、Mn含量分别为14 118.75、27 480.83、1 212.08、479.58、23.54、18.75、45.88μg/g。该方法的加标回收率为94.56%～114.23%。[结论]黄花菜中含有丰富的与健康密切相关的微量元素,具有较高的食用和药用价值。     

Assessing turnover of microbial biomass phosphorus: Combination of an isotopic dilution method with a mass balance model

Microbial biomass phosphorus (P) can play an important role in P cycling and availability to plants by acting as a source (remineralization) or sink (immobilization) of phosphate ions (iP). To assess the role of the microbial P pools, both the dynamics (i.e. the turnover) and the size of the microbial P pools were studied in forest soils. Combining an isotopic dilution method with a modelling approach, we showed the existence of two pools of microbial P with different dynamics and therefore of different importance in soil P availability and cycling. In particular, we showed that the largest pool of microbial P (80%) had a fast turnover (nine days). Microbial P increased with an increase in soil organic matter and represented up to 53% of total P in contrasting forest soils. By combining these results with the turnover times of microbial P obtained in the modelling study, we evaluated that 8.5-17.3 kg P ha⁻¹ of microbial P could turn over in a few days. This suggests that microbial biomass P is a potentially significant source of available iP, and that micro-organisms can play a major role in P cycling in the forest studied here. However, microbial biomass can also be in competition with the trees since most of the remineralized P could be immobilized again in the microbial turnover.     

紫海胆黄脂肪酸的气相色谱-质谱分析

为了了解紫海胆黄中脂肪酸的组成,采用Bligh-Dyer提取法对样品中脂肪油进行提取,甲酯化后利用气相色谱-质谱联用仪进行分析测定。结果发现,从紫海胆黄中共鉴定出14种脂肪酸,饱和脂肪酸6种,相对百分含量占总检出量的32.89%;不饱和脂肪酸8种,相对百分含量占总检出量的67.11%,其中,5,8,11,14,17-二十碳五烯酸(EPA)和4,7,10,13,16,19-二十二碳六烯酸(DHA)的相对百分含量分别为12.73%和1.21%。     

美国公理会与民国保定乡村建设述论

在二十世纪二三十年代中国开展的乡村建设运动中,除以往被学界重视的民间乡建团体外,关注较少的近代来华传教团体也起了非常重要的作用,尤其是在乡建开展较为出色的保定地区,美国公理会可谓翘楚。该会针对保定乡村落后的现状,在此开办平民学校,推广农业改良并提倡农业教育。这些乡村建设活动虽然带有宗教性的功利动机,在开展过程中也遇到了世俗与宗教相冲突的两难境地,但在部分地区的确改进了民众的生活水平,一定程度上缓解了当地乡村社会面貌。     

中国赤眼蜂研究和应用的历史与现状

简要回顾了赤眼蜂在我国研究和应用的历史，并从赤眼蜂的分类、寄生行为、生态特性、大量繁殖和大面积应用几个方面对我国赤眼蜂研究和应用的现状进行了综述。     

弓形体抗原的纯化与分析

对几种提纯弓形体抗原的方法进行了比较。结果,分别经５０００ｒ、１００００ｒ、１５０００ｒ／ｍｉｎ离心３０分钟的粗抗原,用于检测弓形体抗体的Ｐ／Ｎ值依次为５．０５、５．６０、６．４３。用１００００ｒ／ｍｉｎ３０分钟处理的粗抗原（Ｒ１００００）,经凝胶柱层析分离洗脱,呈现２个蛋白峰（Ｆ１、Ｆ２）,经免疫学测定,其主要的抗原活性部分存在于Ｆ１中。Ｒ１００００抗原用５０％硫酸铵沉淀（Ｓ５０）的蛋白质得率达６４％;用７０％硫酸铵沉淀（Ｓ７０）的蛋白质率为３５％。Ｒ１００００与Ｆ１、Ｆ２、Ｓ５０、Ｓ７０５个抗原,经ＥＬＩＢ后用高免兔血清识别的条带数：Ｆ１和Ｆ２各１条、Ｓ５０Ｚ条、Ｓ７０和Ｒ１００００各３条。除Ｆ２之外,３９～４０ＫＤ为４种抗原的共同反应区带。用上述５种抗原致敏反应检测弓形体抗体,以Ｓ５０具有更高的敏感性和特异性。