延迟收获对长江中游春玉米农艺性状及机收质量的影响

为探明长江中游玉米籽粒机械直收适宜品种与配套农艺措施，2018—2019年选用不同玉米品种，测定不同机收时间下玉米关键农艺性状、产量及机收质量指标。结果表明，收获时间对春玉米机收产量与机收质量均有显著影响。延迟1周收获后籽粒容重显著增加，机收产量显著提高，2年平均提高9.72%；而延迟2周收获则有降低机收产量的趋势。2年收获时杂质率总体≤3%，而机收籽粒破碎率与损失率均>5%，是该区域春玉米籽粒机收面临的主要问题。籽粒厚度、籽粒含水率和百粒重是影响机收籽粒破碎率的关键性状，三者与机收籽粒破碎率均呈显著的倒二次曲线关系；玉米的倒伏率、穗位高和重心高度是影响机收损失率的关键性状，倒伏率与机收损失率呈显著正相关，而穗位高和重心高度与机收损失率均呈显著的二次曲线关系。延迟收获能显著降低籽粒含水量，从而降低籽粒破碎率，但继续延迟收获有增加倒伏的风险。综上，长江中游春玉米成熟后适时延迟7~10 d收获，可有效降低籽粒含水量与机收籽粒破碎率，提高玉米籽粒机收产量。     

烘丝温度和时间对生丝机械性能的影响

从刚落下的丝片上摇取小绞丝,分别在25—180℃和30、60、90min下进行干热处理后,测定其机械性能。结果表明:在90—100℃、30—60分钟时,生丝的强伸力、初始模量以及抱合等机械性能都较好,烘丝温度太高,时间太长都会对生丝机械性能产生不良的影响。     

Long-term variation in brown trout, Salmo trutta L., stocking success in a large lake: interplay between availability of suitable prey and size at release

Abstract –  Factors affecting long-term variation in brown trout, Salmo trutta L., stocking success were examined in a large lake, Lake Oulujärvi, in central Finland. Brown trout were stocked in spring (late May to early June) in 1974–1991 and in summer (late June to early July) in 1992–2001. The biomass of the vendace, Coregonus albula (L.), population (prey) at release time had the largest positive effect on stocking success within both periods: biomass of adult vendace in spring and both 0+ and adult vendace in summer. Increasing the size of stocked fish had a positive effect if the vendace available at release were only adults. The increasing trend of predator-catch-per-unit-effort (CPUE) [combined CPUE of northern pike Esox lucius L., burbot Lota lota (L.), and pike-perch Stizostedion lucioperca (L.)] through the study period and its negative effect on trout stocking success suggested an increasing effect of predation within the entire time series.     

A perspective on the measurement of time in plant disease epidemiology

The growth and development of plant pathogens and their hosts generally respond strongly to the temperature of their environment. However, most studies of plant pathology record pathogen/host measurements against physical time (e.g. hours or days) rather than thermal time (e.g. degree-days or degree-hours). This confounds the comparison of epidemiological measurements across experiments and limits the value of the scientific literature.     

The effect of sowing date, stale seedbed, row width and mechanical weed control on weeds and yields of organic winter wheat

Three field experiments were carried out in organically grown winter wheat in Denmark. The treatments were sowing time (normal or late sowing) and false seedbed, row width (12 and 24 cm) and weed control method [untreated; mechanical weed control (weed harrowing at 12 cm supplemented with inter‐row hoeing at 24 cm); and herbicide weed control]. Weed biomass in midsummer was greatest on plots sown at the normal sowing time (compared with delayed sowing) and was reduced by mechanical or chemical weed control (compared with untreated plots). Row width alone had no influence on weed biomass, but in the experiment with high weed pressure, the more intensive mechanical weed control used at a row width of 24 cm reduced weed biomass. Normal sowing time tended to give higher yields, but this was only statistically significant in one of the three experiments. Wide rows gave a yield decrease in the experiment with low weed pressure. The effect of weed control on yield was dependent on the weed pressure. At low weed pressure, mechanical weed control caused a yield decrease compared with untreated or herbicide treated. At intermediate weed levels there were no differences, whereas at high weed pressure, mechanical weed control and herbicide treatment caused a yield increase compared with untreated. False seedbeds were shown to contribute to a decrease in the soil seed reserve.     

Endocannabinoids as endometrial inflammatory markers in lactating Holstein cows

The objective of this study was to consider endocannabinoid system as inflammatory markers in bovine endometrium to better understand the role of this system in regulating many of the functions that are related to inflammatory condition. At day 26 post‐partum, fourteen cows were divided into two groups depending on the inflammatory condition: 1‐ subclinical endometritis (n = 7, with purulent or mucopurulent uterine discharge detectable in the vagina) and 2‐ healthy (n = 7, No (muco)) purulent discharge. Blood samples were collected at 26 and 30 days relative to calving to determine plasma tumour necrosis factor (TNF) and lipopolysaccharide‐binding protein (LBP) concentrations; moreover, uterine biopsy was carried out on day 26 post‐partum to measure mRNA abundance of TNF, interleukin‐1B (IL1B), interleukin‐6 (IL‐6), C‐X‐C motif chemokine ligand 8 (CXCL8), endocannabinoid receptor (CNR2), N‐acyl phosphatidylethanolamine phospholipase D (NAPEPLD), fatty acid amide hydrolase (FAAH), N‐acylethanolamine acid amidase (NAAA) and monoglyceride lipase (MGLL) by real‐time PCR. Results showed mean plasma concentrations of TNF and LBP were lower in healthy cows compared to subclinical endometritis cows (p < .05). Relative mRNA expression for NAAA and FAAH was decreased (p < .05), and relative mRNA expression for CNR2 and NAPEPLD increased in cows with subclinical endometritis compared to healthy cows. In conclusion, relative mRNA expression of TNF, IL1B and CXCL8 and plasma concentration of LBP increased during inflammatory condition along with decreased endocannabinoids hydrolyzing enzyme (NAAA and FAAH), increased enzymes that synthesize endocannabinoids (NAPEPLD) and relative gene expression of the endocannabinoid receptor; together, these contribute to increased endocannabinoids levels during inflammation. Overall, we provide evidence that endocannabinoid system is altered in endometrium tissue during inflammation through increased mRNA expression of CNR2 and synthesis enzyme and decreased mRNA expression of hydrolyzing enzymes interfere with pro‐cytokine production and signalling, which may interfere with the onset and progression of inflammation.     

基于ITS分析云南光叶桑和钦州长果桑在桑属中的亲缘关系及分化时间

云南光叶桑、钦州长果桑在形态分类学上均属同一桑种Morus macroura。通过PCR扩增2份地方品种资源材料的ITS序列并分析序列差异及构建系统进化树,阐明各自在桑属中的遗传分化关系。2份材料的ITS序列长度均为576 bp,其中:云南光叶桑的G+C含量为59.90%,碱基序列45位A变G,560位T变G,与昆明奶桑(Morus macroura)、荥经川桑(Morus notabilis)、云南毛叶奶桑(Morus macroura var.mawa)、云南长穗桑(Morus wittiorum)、云南奶桑(Morus macroura)、雅安华桑(Morus cathayana)同在第Ⅰ类群,有较近的亲缘关系;钦州长果桑的G+C含量为59.72%,碱基序列45位为A,560位T变G,与云南华桑(Morus cathayana)同在第Ⅱ类群,有较近的亲缘关系。应用松散分子钟方法估算云南光叶桑与荥经川桑、雅安华桑、云南长穗桑的分化时间为8.23 Ma,钦州长果桑与云南华桑的分化时间为9.67 Ma,二者起源的地质年代是新第三纪中新世与上新世之交,是为了抵御地球寒冷、旱化,向南、向山地迁移形成的物种。     

高产奶牛孕检后同期发情程序选择的研究

为了研究适用于高产奶牛的同期发情程序方案,将218头膘情良好、子宫和卵巢发育正常的不同胎次荷斯坦牛随机分成两组,试验1组为106头,试验2组为112头,分别采用两种同期程序(0.5.6.8和0.7.8.9)进行处理,测定情期受胎率,用于评价两种同期程序对高产奶牛的适用性.结果表明,试验2组情期受胎率平均为41.96％,...     

温度对海带幼孢子体后期的叶长、叶宽的影响

2014年—2016年,当海带养殖区水温降至19℃时,将海带"奔牛"品系的幼苗移植到荣成养鱼池湾海域,采用垂挂式养殖方式暂养,定期调整水层和摆洗幼苗,采用挂袋施肥的方式施加硫酸铵和硝酸铵的混合肥.约11月中旬,在海带苗种长至12～15 cm时开始分苗,此后在Ⅰ类海带养殖区,按照大单架平养的养殖方式进行正常养殖.自1月中...     

食品安全与食品低温流通中的温度监控

食品的温度监控是一种有效的保证食品安全及保持冷藏链完整的手段,对冷冻冷藏食品在低温流通过程中实行温度监控是非常有必要的。目前,我国冷藏运输中的温度管理情况并不乐观,消费者获得的货物通常不能达到预计的要求。要解决这一问题,必须要借助于时间-温度指示器等来对其整个运输过程进行温度监控。本文对温度立法的必然性和前景,温度监控的重要性、原理以及在冷藏运输中的应用作了较详尽的介绍,并列举了几种国外时间-温度指示器的工作原理。