Effect of number of meals and frequency of feeding on voluntary feed intake of Colossoma macropomum (Cuvier)

Juvenile, 0.87 g Colossoma macropomum (Cuvier) were submitted to different ad libitum feeding regimes. Feeding frequency ranged from one to five meals per day and intervals between meals from 3 h to 24 h. Higher feeding frequencies resulted in higher feed uptake, a higher growth rate and a decreased feed utilization efficiency. Feed consumption was lower at 0700 h than at 1900 h. The amount of feed from different meals persisting in the digestive tract was determined with chromic-oxide-marked feed. This method revealed that with ad libitum feeding, about 21% of the feed remained uneaten. Feed losses did not differ significantly between feeding regimes. Feed accumulated in the digestive tract in the morning and early afternoon. In the late afternoon most feed rests disappeared from the digestive tract and feed consumption increased. It is suggested that feed uptake and growth of C. macropomum can be improved by extending the feeding period after 1900 h.     

Gummy stem blight resistance of cucumbers (Cucumis sativus L.)

Summary A start was made with breeding for resistance to gummy stem blight in cucumber. A method has been development for screening plants in a young stage. Using this method a distinct level of resistance was found in plants of Leningradsky, Wjarnikovsky,a P.I. entry from Birma, Rheinische Vorgebirge and a P.I.entry from Turkey. Lines developed from this material show a higher level of resistance than Dutch slicing and pickling cucumber varieties.     

Factors influencing red expression in autumn foliage of sugar maple trees

We evaluated factors influencing the development of autumn red coloration in leaves of sugar maple (Acer saccharum Marsh.) by measuring mineral nutrient and carbohydrate concentrations, water content, and phenology of color development of leaves from 16 mature open-grown trees on 12 dates from June through October 1999. Mean foliar nutrient and carbohydrate concentrations and water content were generally within the range published for healthy sugar maple trees. However, foliar nitrogen (N) concentrations were near deficiency values for some trees. The timing and extent of red leaf coloration was consistently correlated with both foliar N concentrations and starch or sugar concentrations, which also varied with N status. Leaves of trees with low foliar N concentrations turned red earlier and more completely than those of trees with high foliar N concentrations. Low-N trees also had higher foliar starch concentrations than high-N trees. During the autumn development of red leaf coloration, foliar starch, glucose and fructose concentrations were positively correlated with red leaf color expression. At peak red expression, the concentrations of glucose, fructose, sucrose and stachyose were all positively correlated with red color expressed as a percent of total leaf area.     

Electrical stunning followed by decapitation or chilling of African catfish (Clarias gariepinus): assessment of behavioural and neural parameters and product quality

The objective of this study was to assess neural and behavioural responses in farmed African catfish (Clarias gariepinus) upon electrical stunning in combination with decapitation or chilling. To assess the possibility of scaling up one or both experimental methods, two trials were performed in an experimental setting. The product quality of the collected samples was compared with the currently applied industrial method: live chilling. After electrical stunning in combination with decapitation, the fish showed spikes alternated with theta and delta waves on the EEG, followed by minimal brain activity after 20±10 s. The same traces on the EEGs were observed after electrical stunning in combination with chilling. Here, minimal brain activity occurred after 22±11 s. Within a confidence level of 95%, the percentage of African catfish that was effectively stunned after administration of an electrical current of 1.5 A dm⁻², 300 V (50 Hz a.c.), followed by decapitation or chilling was above 91%. The analysis yield and evolution of liquid loss showed significant (P<0.05) differences among the batches, which could be explained by the stunning method used. The course values of the pH in the different batches were significantly (P<0.05) dependent on the stunning method, sex and location (visceral or skin side). It is concluded that African catfish can be stunned effectively using electrical stunning in a water tank, followed by decapitation or chilling in ice. Dutch commercial processors prefer to combine electrical stunning with chilling in flake ice in a rotating tumbler, as the outer slime layer is then removed, which facilitates further processing.     

A review of carbon isotopes of phytoliths: implications for phytolith-occluded carbon sources

Journal of Soils and Sediments - Phytolith-occluded carbon (PhytOC) is mainly derived from the products of photosynthesis, which can be preserved in soils and sediments for hundreds-to-thousands of...     

Parentage assignment in Haliotis midae L.: a precursor to future genetic enhancement programmes for South African abalone

The establishment and evaluation of family lines using pedigree information provides an advanced understanding of the variability that exists for complex, economically valuable traits and is a necessary step in the execution of an effective breeding programme. The aim of this study was to assign parentage to mass‐spawned Haliotis midae juveniles using species‐specific microsatellite markers. Screening of wild abalone individuals revealed that the nine loci selected complied with the minimum requirements for parentage analyses: a null allele frequency <5% as well as a high number and frequency of alleles per locus. A total of 598 individuals were genotyped (198 breeding individuals and 400 F1 progeny) from two farms, with parentage results yielding 91% and 90% successful assignment for Farms A and B respectively. This study, therefore, provided the necessary pedigree information required for controlled breeding of individual adult abalone and indicated the usefulness of the panel of microsatellite markers selected for parentage assignment.     

基于ANUSPLIN的时间序列气象要素空间插值

【目的】介绍ANUSPLIN在黄土高原多沙粗沙区时间序列气象要素的空间插值过程,为相关人员在ANUSPLIN的参数设置、误差分析和协变量要素选择等方面提供参考。【方法】以薄盘样条函数为插值理论,以专用气象数据插值软件ANUSPLIN为实现工具,并引入一个或多个协变量线性子模型,来实现多个气象要素的空间插值。【结果】完成了黄土高原多沙粗沙区时间序列(1980~2000年)多个气象要素月平均数据的栅格化,计算了气象要素随其影响因子变化的关系。【结论】ANUSPLIN以薄盘光滑样条函数为理论基础,引入协变量线性子模型,能较好地提高气象要素空间插值精度,且能反映气象要素随其影响因子变化的比率关系。在大多数情况下,该区模型选择以样条次数为3次的局部薄盘光滑样条函数模型为最佳。温度的空间插值相对比较容易,且误差较小,1995-07平均相对误差为1%;风速、水汽压的误差中等;日照时数和降雨量的误差较大,个别情况相对误差可超过50%。     

甜瓜属野生种Cucumis hystrix Chakr.胞质葡萄糖-6-磷酸脱氢酶基因的克隆与启动子结构分析

根据植物葡萄糖-6-磷酸脱氢酶(G6PDH,EC1.1.1.49)氨基酸保守区域,设计简并引物,采用RT-PCR技术克隆得到甜瓜属野生种Cucumis hystrix Chakr.(2n=24)G6PDH基因cDNA片段;随后基于该序列设计特异引物,PCR方法筛选野生种BAC文库,获得2个BAC阳性单克隆。测序后获得了G6PDH基因全序列及其上游启动子序列,GenBank登录号:JQ771576。序列分析显示:G6PDH基因全长约6.5 kb,由15个外显子和14个内含子组成;内含子序列均符合5’-gt-ag-3’结构。外显子拼接后获得了G6PDH基因的开放阅读框(ORF)序列,序列全长1 551 bp,编码516个氨基酸,与黄瓜基因组网站公布的G6PDH基因核苷酸序列和氨基酸序列同源性分别为98.71%和99.03%。野生种G6PDH氨基酸序列N端缺少转运肽序列,确定为野生种胞质G6PDH。氨基酸序列与烟草、马铃薯、荷兰芹、猕猴桃、拟南芥、大豆、小麦、玉米、葡萄、杨树等植物胞质G6PDH同源性高达77%以上。系统发育树分析发现,甜瓜属胞质G6PDH与茄科植物最先聚类,植物胞质G6PDH在分子进化水平上与物种进化相符。启动子结构分析表明:序列含有启动子基本元件TATA-box、CAAT-box,还含有丰富的光响应元件,与环境胁迫响应相关的不同顺式作用元件,促进高水平转录的5UTR Py-rich stretch元件和提高表达的CAT-box元件等。     

Foliar Nitrogen Uptake from Wet Deposition and the Relation with Leaf Wettability and Water Storage Capacity

This study assessed the foliar uptake of ¹⁵N-labelled nitrogen (N) originating from wet deposition along with leaf surface conditions, measured by wettability and water storage capacity. Foliar ¹⁵N uptake was measured on saplings of silver birch, European beech, pedunculate oak and Scots pine and the effect of nitrogen form (NH ₄ ⁺ or NO ₃ ^? ), NH ₄ ⁺ to NO ₃ ^? ratio and leaf phenology on this N uptake was assessed. Next to this, leaf wettability and water storage capacity were determined for each tree species and phenological stage, and the relationship with ¹⁵NH ₄ ⁺ and ¹⁵NO ₃ ^? uptake was examined. Uptake rates were on average five times higher (p?<?0.05) for NH ₄ ⁺ than for NO ₃ ^? and four times higher for deciduous species than for Scots pine. Developing leaves showed lower uptake than fully developed and senescent leaves, but this effect was tree species dependent. The applied NH ₄ ⁺ to NO ₃ ^? ratio did only affect the amount of N uptake by senescent leaves. The negative correlation between measured leaf contact angles and foliar N uptake demonstrates that the observed effects of tree species and phenological stage are related to differences in leaf wettability and not to water storage capacity.