Belowground Bud Bank Is Insensitive to Short-Term Nutrient Addition in the Meadow Steppe of Inner Mongolia

Human activities and industrialization have significantly increased soil nutrients,such as nitrogen(N)and phos-phorus(P),profoundly impacting the composition and structure of plant community,as well as the ecosystem functions,especially in nutrient-limited ecosystems.However,as the key propagule pool of perennial grasslands,how belowground bud bank and its relationship with aboveground vegetation respond to short-term changes in soil nutrients was still unclear.In this study,we conducted a short-term(2021–2022)soil fertilization experiment with N addition(10 g N m^(-2) yr^(-1))and P addition(5 g N m^(-2) yr^(-1))in the meadow steppe of Inner Mongolia,China,to explore the responses of belowground bud bank,aboveground shoot population and their relationships(represented by the ratio of bud to shoot density-meristem limitation index(MLI))for the whole community and three plant functional groups(perennial rhizomatous grasses-PR,perennial bunchgrasses-PB,and perennial forbs-PF)to nutrient addition.The short-term nutrient addition had no significant influences on belowground bud density,aboveground shoot density,and MLI of the whole plant community.Plant functional groups showed different responses to soil fertilization.Specifically,N addition significantly increased the bud density and shoot density of PR,especially in combination with P addition.N addition reduced the shoot density of PF but had no influence on its bud density and MLI.Nutrient addition had significant effects on the three indicators of PB.Our study indicates that the belowground bud bank and its relationship with aboveground vegetation in temperate meadow steppe are insensitive to short-term soil fertilization,but plant functional groups exhibit specific responses in terms of population regeneration,which implies that plant community composition and ecosystem functions will be changed under the ongoing global change.

温带半干旱草原克隆禾草叶性状对氮沉降铵硝比输入的响应:叶序不可忽略

叶片是植物光合作用的主要器官。叶片可塑性在很大程度上决定了植物对富氮环境的适应。然而在自然条件和富氮环境中,测定植物叶片性状时需要采集的最佳数量或比例是否一致并不明确;同时大气氮沉降主要组分铵态氮与硝态氮比例变化是否会改变叶片最佳测量数量缺少实验证据支撑。因此本研究依托自2014年在中国北方温带草原开展的铵硝比添加实验(即对照和5:1、1:1和1:5的NH_(4)^(+)-N/NO_(3)^(−)-N比例),于2020年8月(植物群落生物量高峰时期)测量了两个形态相似的优势多年生禾本科物种(即羊草和冰草)在叶序水平的叶面积、叶厚度和叶绿素含量。我们发现在对照处理(自然条件),除羊草叶面积需要测定5片(占单株总叶片数的78.82%),其它性状通过测量两片完全展开叶即可代表整株该叶性状的单叶平均特征。铵硝比添加处理显著改变了叶性状最大值所在叶序,导致需要增加叶片测定数才能代表整株叶片的单叶平均特征。铵硝比添加显著改变了受叶序调控的叶性状间权衡关系,即叶片虽变大却变薄。因此,本研究结果表明,通过测量全部完全展开叶或者提供一个合适的尺度推绎参数方能更好地评估氮沉降效应下植株叶片性状的响应特征。

Influence of physiological and environmental factors on the diurnal variation in emissions of biogenic volatile compounds from Pinus tabuliformis

Biological volatile organic compounds(BVOCs) have a large influence on atmospheric environmental quality, climate change and the carbon cycle. This study assesses the composition and diurnal variation in emission rates of BVOCs from Pinus tabuliformis, using an enclosure technique. Environmental parameters(temperature and light intensity) and physiological parameters(net photosynthetic rate, P_n; stomatal conductance, g_s; intercellular CO_2 concentration, C_i; and transpiration rate, T_r) that may affect emission behavior were continuously monitored. The 10 most abundant compound groups emitted by P. tabuliformis were classified by gas chromatography–mass spectrometry. The dominant monoterpenoid compounds emitted were α-pinene, β-myrcene, α-farnesene and limonene. The diurnal emission rate of BVOCs changed with temperature and light intensity, with dynamic analysis of BVOCs emissions revealing that their emission rates were more affected by temperature than light. The variation in monoterpene emission rates was consistent with estimates of P_n, g_s and T_r. Basal emission rates(at 30 °C,) of the main BVOCs ranged from 0.006 to 0.273 μg^(-1)/(hr g),while the basal ER standardization coefficients ranged from 0.049 to 0.144 °C^(-1). Overall, these results provide a detailed reference for the effective selection and configuration of tree species to effectively prevent and control atmospheric pollution.

The Establishment and Validation of the Human U937 Cell Line as a Cellular Model to Screen Immunomodulatory Agents Regulating Cytokine Release Induced by Influenza Virus Infection

Severe influenza infections are often associated with the excessive induction of pro-inflammatory cytokines,which is also referred to as"cytokine storms".Several studies have shown that cytokine storms are directly associated with influenzainduced fatal acute lung injury and acute respiratory distress syndrome.Due to the narrow administration window,current antiviral therapies are often inadequate.The efforts to use immunomodulatory agents alone or in combination with antiviral agents in the treatment of influenza in animal models have resulted in the achievement of protective effects accompanied with reduced cytokine production.Currently,there are no immunomodulatory drugs for influenza available for clinical use.Animal models,despite being ideal to study the anti-inflammatory responses to influenza virus infection,are very costly and time-consuming.Therefore,there is an urgent need to establish fast and economical screening methods using cellbased models to screen and develop novel immunomodulatory agents.In this study,we screened seven human cell lines and found that the human monocytic cell U937 supports the replication of different subtypes of influenza viruses as well as the production of the important pro-inflammatory cytokines and was selected to develop the cell-based model.The U937 cell model was validated by testing a panel of known antiviral and immunomodulatory agents and screening a drug library consisting of 1280 compounds comprised mostly of FDA-approved drugs.We demonstrated that the U937 cell model is robust and suitable for the high-throughput screening of immunomodulators and antivirals against influenza infection.