Inhibition of ammonia-oxidizing bacteria promotes the growth of ammonia-oxidizing archaea in ammonium-rich alkaline soils

Disparities in the substrate affinity and tolerance threshold for ammonia have been believed to play a key role in driving niche differentiation between ammonia-oxidizing archaea (AOA) and bacteria (AOB); however, recent surveys argue that direct competition between AOA and AOB is also important in this phenomenon. Accordingly, it is reasonable to predict that diverse AOA lineages would grow in ammonium (NH₄⁺)-rich alkaline arable soils if AOB growth is suppressed. To test this hypothesis, a microcosm study was established using three different types of alkaline arable soils, in which a high NH₄⁺ concentration (200 μg N g^-1 dry soil) was maintained by routinely replenishing urea and the activities of AOB were selectively inhibited by 1-octyne or 3,4-dimethylpyrazole phosphate (DMPP). Compared with amendment with urea alone, 1-octyne partially retarded AOB growth, while DMPP completely inhibited AOB. Both inhibitors accelerated the growth of AOA, with significantly higher ratios of abundance of AOA to AOB observed with DMPP amendment across soils. Nonmetric multidimensional scaling analysis (NMDS) indicated that different treatments significantly altered the community structures of both AOA and AOB and AOA OTUs enriched by high-NH₄⁺ amendment were taxonomically constrained across the soils tested and closely related to Nitrososphaera viennensis EN76 and N. garnensis. Given that these representative strains have been demonstrated to be sensitive to high ammonia concentrations, our results suggest that it is the competitiveness for ammonia, rather than disparities in substrate affinity and tolerance threshold for ammonia, that drives niche differentiation between these phylotypes and AOB in NH₄⁺-rich alkaline soils.     

降水梯度对青海湖河源湿地温室气体排放日变化的影响

水分是影响高寒生态系统生长发育的主要限制因素,为探明不同水分条件对湿地温室气体排放特征的影响,选取青海湖流域瓦颜山河源湿地为研究对象,利用不同的水分特征湿地,通过静态箱-气相色谱法,监测了湿地24 h温室气体排放特征,探究了2020年和2021年8月（生长旺季）的CK（对照处理）、+25%（增雨25%处理）、-25%（减雨25%处理）、+75%（增雨75%处理）、-75%（减雨75%处理）条件下,对二氧化碳（CO₂）、甲烷（CH₄）、氧化亚氮（N₂O）日变化趋势。结果表明：（1）CO₂排放范围为47.52～123.71 mg·m^-2·h^-1,CH₄通量范围为-8.50～6.74μg·m^-2·h^-1,N₂O通量范围为-15.82～6.90μg·m^-2·h^-1。（2）CK、+25%、+75%处理下CO₂、CH...     

双层播种对大蒜农艺性状的影响

以成都二水早大蒜品种为试材,研究2种种植密度及单层、双层2种播种模式对大蒜农艺性状的影响。试验结果表明,采用双层播种或加大种植密度,对大蒜植株株高、假茎高没有显著影响,但对鳞茎大小、抽薹率、独蒜率有极显著的影响。随着种植密度的增加,蒜头直径随之变小、抽薹率下降、独蒜率提高。     

香叶树挥发油、油脂等主要成分分析

The components of essential oil and fat in different parts of Chinese spicehush (Lindera communis) were extracted and analyzed. By comparing the essential components, it was found that the essential oil content in different parts of the tree was peel > fruit > twig> branch > leaf > kernel, and the highest content was up to 8.0 mL·kg^-1 in peel. The glaucic acid, 1H-Cycloprop [e] azulene, decahydro-1, 1, 7-trimethyl-4-methylene-, [1aR-(1a.α., 4a. α., 7.α., 7a.β), 7b.α.)] and caryophyllene oxide were the major components of the essential oils. The oil contents of the fruit, peel and kernel were 45.2%, 39.1% and 60.4% respectively. The main fatty acid compositions of the fruit were lauric acid (44.77%), decanoic acid (12.92%), oleic acid (10.91%), 11-oleic acid (9.84%), palmitic acid (6.91%), and linoleic acid (5.12%). The unsaturated fatty acid content in the peel is higher, and the total content of 11-oleic acid (28.06%), oleic acid (27.02%), linoleic acid (13.50%), palmitoleic acid (7.84%) is 76.42%. Lauric acid (72.07%) and decanoic acid (21.13%) were the two main fatty acid compositions in kernels, which were accounted for 93.20% of total fatty acids. After the oil was extracted, the protein was richer in kernel cake than in other samples, and the content was 41.56 g·100 g^-1. In this paper, the main oils from L. communis were analyzed, and the results could be used to lay a basis for the comprehensive utilization of L. communis.     

柞蚕茧质性状的遗传效应与杂种优势分析

为了解柞蚕茧质性状的遗传规律和群体杂种优势的表现,对柞蚕3个品种采用完全双列杂交试验设计,利用加性-显性遗传模型(AD模型)和MINQUE(1)统计分析方法分析柞蚕茧质性状的遗传表现。结果表明:全茧量和茧层量同时受加性基因和显性基因的控制,茧层率则主要受显性基因的控制;遗传率的大小顺序为全茧量>茧层量>茧层率;3个茧质性状均表现为正向的群体平均优势,且F2代的优势减半;全茧量表现为负向的群体超亲优势,茧层量F1代的群体超亲优势不明显,F2代表现为负向的群体超亲优势,茧层率则表现为正向的群体超亲优势。3个供试柞蚕品种中,582的全茧量和茧层量具有较高的基因加性效应值,适合作为高全茧量和茧层量育种的杂交亲本。     

北京地区荷斯坦青年牛繁殖性状影响因素分析

本研究利用北京地区23个奶牛场105头公牛的25705个女儿繁殖记录,对中国荷斯坦青年牛的4个繁殖性状,包括青年牛初配日龄（AFI）、青年牛妊娠日龄（AFP）、青年牛初产日龄（AFC）和输精次数（NS）,采用固定模型通过SAS9.1软件GLM过程进行统计分析。结果表明,牛场、出生年份、出生季节以及公牛等效应对青年牛繁殖性状具有显著（P〈0.05）或极显著影响（P〈0.01）。通过提高饲养管理水平,给母牛创造良好的生存环境,选用具有优秀繁殖性能的种公牛,可有效提高母牛繁殖效率。     

整合禽网状内皮组织增殖病病毒基因的鸡痘病毒野毒株致病性研究

以分离保存的整合禽网状内皮组织增殖病病毒（REV）基因的鸡痘病毒（FPV）野毒株接种CEF细胞,间接免疫荧光试验检测REV,结果未检测到游离REV病毒粒子;以该毒株人工感染7日龄SPF雏鸡,同时设阴性对照,常规免疫新城瘦弱毒苗（ND）。接毒后每周采血动态检测NDV抗体、REV抗体、REV病毒血症;同时对试验鸡免疫器官指数、组织学变化动态观察,并对免疫器官的细胞凋亡动态检测。结果表明,整合REV基因的FPV感染后2周可引起鸡REV病毒血症,并产生REV抗体;导致中枢免疫器官发育分化不良,尤其对胸腺的影响最为明显,攻毒2周后,试验组与对照组相比,胸腺指数明显下降（P〈o．05）;免疫器官主要表现实质细胞数量少,正常结构发育不良,间质结缔组织增生而发生纤维化;细胞凋亡检测证实免疫器官的淋巴细胞和巨噬细胞均有明显的凋亡现象,细胞凋亡是引起免疫器官萎缩的主要原因。对新城疫疫苗免疫反应呈显著的抑制作用,攻毒3周后,试验组血清新城疫病毒抗体滴度显著低于对照组（P〈0．05）,其抗体滴度峰值低,维持时间短,下降速度快。本试验证实FPV整合REV前病毒基因组会明显改变FPV的致病性,表现某些REV的致病特征,使感染鸡REV抗体转为阳性并出现病毒血症,进一步证实REV可以通过基因组整合于FPV而进行传播的推测。     

青枯雷尔氏菌胁迫对烟草植株抗氧化酶系活性的影响

以青枯雷尔氏菌RS-1403作为外源微生物,研究不同浓度青枯雷尔氏菌胁迫对烟草植株叶片PPO、POD、SOD酶活性的影响。结果表明:PPO和POD酶活性总和显著高于对照,而SOD酶活性总和除了处理2(接种浓度为2.35×10~4CFU/mL)外,其余的各个处理的均低于对照。烟草植株的根部、茎部和叶片的POD、PPO和SOD酶活性总和明显高于对照处理,并且其酶活性达到高峰的时间有所不同。胁迫接种5 d后,烟草植株叶片和茎部的POD酶活性和对照处理的比值最大,胁迫接种10 d后,烟草植株根部POD酶活性比值最大。烟草植株叶片和根部在接种15 d后,PPO酶活性和对照处理的比值达到最大,茎部PPO酶活性在接种5 d后比值最大。接种20 d后,处理烟草植株叶片和茎部的SOD酶活性和对照处理的比值达到最大,接种后25 d,根部SOD酶活性比值最大。     

不同铁制剂对石灰性土壤条件下猕猴桃缺铁黄化的矫治效果

为明确陕西杨凌渭河滩地猕猴桃出现黄化现象的原因,通过对喷施铁制剂矫正效果的比较,筛选出理想的铁制剂用于果树缺铁黄化病防治。以陕西杨凌西桥村出现缺铁黄化的猕猴桃园为研究对象,采用土壤诊断和叶片诊断等方法确定黄化的原因,并以清水为对照,喷施不同铁制剂(硫酸亚铁、柠檬酸铁、复合氨基酸铁、乳酸亚铁和腐殖酸铁)进行矫治,检测其对猕猴桃叶片叶绿素和有效铁含量及果实品质的影响。结果表明,猕猴桃黄化原因不仅仅是由于土壤有效铁含量低,还与植株吸收能力不同有关。由于植株过多吸收P、K、Zn、Mn等元素,引起养分不平衡而导致对铁吸收产生拮抗作用也是产生缺铁黄化的原因之一。不同铁制剂对猕猴桃黄化的矫治效果有差异,其中以柠檬酸铁和复合氨基酸铁的处理效果最好,显著提高了猕猴桃叶片的叶绿素和有效铁含量以及果实中维生素C、可溶性固形物、全铁的含量,有效改善了果实品质。在供试的几种铁制剂中,柠檬酸铁和复合氨基酸铁是矫治果树缺铁黄化的最理想制剂。     

梨枣幼树生长发育对底施氮肥反应的研究初报

对不施氮肥、根围无氮肥和混匀施氮肥三种情况下盆栽梨枣幼树地上部和根系的生长状况、土壤速效氮含量以及氨挥发速率进行了测定,探讨梨枣幼树生长发育对氮肥的反应及其原因.结果表明:不施肥时,梨枣幼树地上部生长量及根系数目与鲜重显著大于其他两个处理,生长状况良好;根围无肥的梨枣幼树在栽植早期阶段生长状况良好,后期长势缓慢甚至出现...