蜈蚣草中砷与磷、钾、钙等营养元素的交互作用

砷污染对植物、动物和人体均产生毒害作用。研究砷元素与磷、钾、钙等元素的交互作用,结果表明:在蜈蚣草体内磷的浓度会随着培养液中砷浓度的增加而增加,两者并不存在拮抗关系;蜈蚣草羽叶表皮细胞中砷和钾浓度呈显著正相关;蜈蚣草中砷的累积量会同时受介质中砷水平和钙水平的限制。在提高介质中的砷浓度时,蜈蚣草根部的镁浓度逐渐降低,但对叶柄和羽叶中的镁浓度无显著影响。     

不同氮磷浓度对蛋白核小球藻砷富集和转化的影响

氮(N)、磷(P)是影响蛋白核小球藻生长的重要因素,通过改变培养液中N、P的浓度,可能实现对蛋白核小球藻富集砷(As)进行调控。为探讨N、P浓度对这种微藻吸收As的影响是否与其生长变化有关,采用室内培养实验,首先研究不同N、P浓度对蛋白核小球藻生长的影响;进而选择不影响小球藻生长的N(247、24.7 mg·L-1)、P(6、0.6 mg·L-1)浓度组合,设置0.8、8 mg·L-1的亚砷酸盐(As3+)和砷酸盐(As5+)处理3 d,研究N、P浓度对小球藻As富集和转化的影响。结果表明,当P浓度为6 mg·L-1时,N浓度降低到24.7 mg·L-1不会影响小球藻对As3+和As5+的富集及其胞内As形态的转化;而当N浓度为247 mg·L-1时,P浓度降低到0.6 mg·L-1则会显著增加小球藻对As3+和As5+的吸收和富集,藻细胞内As5+还原、甲基化和外排也显著增强。因此,在不影响小球藻细胞生长的条件下,P对其As富集和转化过程的影响比N更为显著。     

基于注意力机制的小样本啤酒花病虫害识别

为提高啤酒花产业的品质和产量,针对于传统人工识别鉴定难度大,效率低和客观性不够,以及啤酒花病虫害识别无大型公开数据集等问题.本文提出一种基于软注意力机制的小样本啤酒花病虫害识别方法,对传统深度残差网络ResNet模型进行改进,并使用图像增强技术-直方图均衡化处理图片得到新的数据集.实验结果表明,在小样本情况下,相比于传...     

食品添加剂磷酸氢二铵中砷含量的测定

运用原子荧光光谱法对进出口食品添加剂磷酸氢二铵中砷含量进行了测定,通过线性范围、检出限、精密度、回收率和实验室间比对测试,证明了原子荧光光谱法能快速、准确地检测出进出口食品添加剂中砷的含量。该方法线性关系良好,检出限低,准确度高,重复性和再现性好,可广泛用于进出口食品添加剂中砷含量的检测。     

梨幼树到结果初期春施15N–尿素的利用及其在土壤的残留与损失

2014—2016年,以‘黄冠’梨为材料,采用15N示踪技术研究了从幼树期到结果初期梨树对春季施用氮素的吸收利用及土壤残留与损失情况。研究结果表明,幼树期(2014—2015年)梨树生长以中心干和粗根等树体骨干结构建立为主,生长量相对较小;进入结果初期(2016年)后树体生长表现为树体骨干结构建立为主,枝梢等营养器官生长与产量形成并存,生长量大幅增加。整个试验期间,树体贮藏器官的标记氮素吸收量较大,其中幼树期中心干吸收量最大,结果初期粗根吸收量最大。0~100 cm土层标记氮素残留量随土层深度和施用年限增加逐渐降低,其中,施用标记氮素后第1年(2014年),土壤标记氮素残留量较高,残留率达63.61%,梨幼树对标记氮素利用率仅为3.25%。随后两年(2015—2016年)土壤残留量较低,树体对标记氮素利用率仅为0.51%和0.80%。试验结束时,幼树期到结果初期梨树对标记氮素的累计利用率为4.57%,土壤标记氮素残留量为20.34%,损失率达75.07%。     

残膜回收机带式卷膜装置设计与试验

为解决现有残膜回收机集膜装置在集膜和卸膜过程中残膜质地松散、作业效率低等问题,设计了一种带式卷膜装置.阐述了该带式卷膜装置的基本结构和工作原理,通过理论分析确定了关键部件结构参数,分析了卷膜作业过程,经过计算分析得到可卷收残膜膜卷的最大直径、卷膜速比范围、卷膜倾角范围.采用三因素三水平Box-Behnken试验设计方法...     

超高效液相色谱-质谱/质谱法同时测定蔬菜中7种磺胺的残留量

为建立超高效液相色谱-质谱/质谱法(UPLC-MS/MS)同时测定蔬菜中7种磺胺残留量的方法。样品用1%乙酸乙腈提取，以C18色谱柱分离待测物，采用多反应监测(MRM)离子扫描模式，外标法进行定量，线性良好，相关系数均大于0.999。结果显示：7种磺胺的检出限为0.000 4～0.000 6 mg/kg，样品添加回收率为67.5%～94.1%，相对标准偏差均少于5.3%(n＝6)。该方法简单快捷、定量准确，可满足多种蔬菜中7种磺胺的残留检测要求。     

Fertilizer value of nitrogen in hen and broiler manure after application to spring barley using different application timing

The nitrogen (N) fertilizer effect of layer hen and broiler manure applied at different times on spring barley yield was studied in seven Swedish field experiments during 2005–2008. Two experiments had parallel field incubations to study N release after fertilizer application. The effect of total N in manure on N offtake was 30–40% that of mineral N, except in a dry year, when the effect was very low. Although the relative proportions of ammonium N, uric acid N and other N differed between the hen and broiler manure, the effect of total N was similar for both. In field incubations, mineral N decreased from 75 to 60% of total N applied in hen manure, whereas it increased from 20 to 50% in broiler manure, because of net immobilization and release, respectively. The limited fertilizer nitrogen replacement value, corresponding to only 30–40% of total N, could be as a result of ammonia volatilization after rather shallow incorporation with harrow. Net N release from broiler manure lasted for 6–8 weeks after application, after which it generally ceased. In some cases, manure application in early spring gave better yield effects than application at sowing, probably because of better synchronization of the N release with crop N requirements. The residual N effect on the N offtake in crop in the year after manure application was on average 3% of the total N applied, equivalent to a fertilizer replacement value of about 6%.     

Importance of Noncrystalline Hydroxide Phases in Sequential Extractions to Fractionate Antimony in Acid Soils

Abstract

Sequential extraction techniques have been used to make inferences about speciation of phosphorus (P) and to a lesser extent arsenic (As) in soils. However, sequential extraction studies on the less‐abundant group V element, antimony (Sb), are limited. In this work, a widely used P sequential extraction scheme was modified and used to extract P, As, and Sb from two acidic soils from the Macleay River floodplain, NSW, that were enriched with Sb (26.9 and 23.0 mg kg^?1). An ammonium oxalate–oxalic acid step was included in the extraction sequence to dissolve the noncrystalline iron (Fe) and aluminium (Al) hydroxide phase. It extracted 30 to 47% of Sb, indicating the importance of this fraction, which may be mobilized in the floodplain by acid sulfate soil processes and periodic waterlogging. The original method overestimated P, As, and Sb in the residual fraction (30–71%). Relative efficiency values of extracts for P, As, and Sb were compared, and inferences about phase distributions were made. The results suggest some potential in using extractions to assess bioavailability of Sb in soil.     

Genetic potential for residual feed intake and diet fed during early- to mid-gestation influences post-natal DNA methylation of imprinted genes in muscle and liver tissues in beef cattle

Discovery of epigenetic modifications associated with feed efficiency or other economically important traits would increase our understanding of the molecular mechanisms underlying these traits. In combination with known genetic markers, this would provide opportunity to improve genomic selection accuracy in cattle breeding programs. It would also allow cattle to be managed to improve favorable gene expression. The objective of this study was to identify variation in DNA methylation between beef cattle of differential pre-natal nutrition and divergent genetic potential for residual feed intake (RFI). Purebred Angus offspring with the genetic potential for either high (HRFI) or low (LRFI) RFI were prenatally exposed to either a restricted maternal diet of 0.5 kg/d average daily gain (ADG) or a moderate maternal diet of 0.7 kg/d ADG from 30 to 150 d of gestation. We performed DNA methylation analysis of differentially methylated regions (DMR) of imprinted genes (Insulin-like growth factor 2 (IGF2) DMR2, IGF2/H19 imprinting control region (ICR) and IGF2 receptor (IGF2R) DMR2) using post-natal samples of longissimus dorsi (LD) muscle taken from male and female calves at birth and weaning, and of LD muscle, semimembranosus (SM) muscle, and liver samples collected from steers at slaughter (17 months of age). Interestingly, for all three DMR investigated in liver, LRFI steers had higher levels of methylation than HRFI steers. In LD muscle, IGF2/H19 ICR methylation differences for heifers at birth were due to pre-natal diet, while for steers at birth they were mostly the result of genetic potential for RFI with LRFI steers again having higher levels of methylation than HRFI steers. While results from repeated measures analysis of DNA methylation in steers grouped by RFI revealed few differences, in steers grouped by diet, we found higher methylation levels of IGF2 DMR2 and IGF2R DMR2 in LD muscle of restricted diet steers at weaning and slaughter than at birth, as well as increased methylation in LD muscle of restricted diet steers compared with moderate diet steers at weaning and/or slaughter. Our results suggest that differential pre-natal nutrition, and divergent genetic potential for RFI, induces tissue- and sex-specific alterations in post-natal IGF2 and IGF2R methylation patterns and that these patterns can vary with age in Angus beef cattle.