豆-禾混播草地中紫花苜蓿比例对其固氮效率的影响及潜在生理机制

【目的】 通过研究豆草比例对紫花苜蓿-羊草混播草地豆科植物生物固氮的影响及其生理生态机制,深化对混播群落结构和生物固氮功能关系的理解,辅助豆-禾混播草地的科学建植和管理,提高混播草地生物固氮和土壤肥力,提升草地资源生产和生态保障能力。【方法】 2017年5月,利用紫花苜蓿和羊草为试验材料,采取随机区组设计,于中国科学院长岭草地农牧生态研究站内建植不同豆草比例（紫花苜蓿占比为25%、50%、75%、100%）的紫花苜蓿-羊草混播草地,4次重复。建植一年后,通过样方取样法调查混播草地群落结构变化,测定紫花苜蓿叶片、枝条和根系生长发育、光合和水分等生理代谢特征,在测定根系结瘤特征基础上,采取¹⁵N同位素自然丰度法评估紫花苜蓿固氮效率,结合土壤水分动态监测,分析豆草比例对紫花苜蓿生物固氮的影响及其生理生态机制。【结果】 （1）混播草地建植一年后,对应25%、50%、75% 和100%设计的豆草混播比例,混播草地实际紫花苜蓿占比分别为11%、27%、53%和100%。（2）对比25%、75%和100%的初始豆草种植比例,50%的初始豆草比例下,生长季平均土壤水分含量分别增加了21.4%、36.4%和51.7%。（3）50%豆草种植比例下,紫花苜蓿植株有更大的枝条和根系生物量、叶片数量、叶片面积、叶片厚度和叶片生物量,上述指标最小值出现在100%的豆草播种比例。（4）50%豆草种植比例下,紫花苜蓿具有最大的光合速率,枝条和根系中淀粉含量最高,但枝条和根系中可溶性糖含量最低。（5）50%的初始豆草混播比例下,紫花苜蓿根瘤发育更完善,其生物固氮率较25%、75%和100%的豆草混播比例分别提高了13.5%、44.6%和79.2%。回归分析表明,随豆草比例变化,紫花苜蓿生物固氮效率与土壤含水量呈正相关。【结论】 紫花苜蓿-羊草混播草地中,紫花苜蓿生物固氮能力与豆草比例间存在非直线型变化关系。当初始豆草种植比例为50%时,紫花苜蓿生物固氮率最大。豆草比例驱动土壤水分变化,进而通过调控叶片发育和光合等途径改变了紫花苜蓿植株和根瘤发育,是其影响生物固氮的潜在机制。     

心尖锚的力学分析

设计了一种六齿镍钛合金锚钩用于封堵器等二尖瓣、三尖瓣返流修复系统的心尖固定,并对其力学特性进行研究.通过分析心脏结构及解剖数据,确定锚钩形状和可控尺寸设计变量,利用Solidworks建立锚钩3D模型,运用Abaqus软件对23个不同尺寸锚钩模型的入鞘过程进行有限元计算,分析锚钩入鞘过程中的最大入鞘力、最大冯米塞斯应变和入鞘轨迹的影响因素.制作了一种规格锚钩实物,与计算结果进行对比分析.结果表明:鞘部长度、鞘部角度及齿宽对应力、应变的影响最大,可以通过减小鞘部长度、鞘部角度及齿宽,有效降低最大应力、应变值;厚度、曲率半径及齿宽对入鞘力起到决定性作用,而根长和角度对入鞘力的影响很小;轴向刺入深度主要通过控制鞘部长度及鞘部角度来定义,径向刺入深度则由曲率半径的大小所决定.研究可为需心尖固定的心脏介入产品设计提供一定的借鉴意义.     

Is N‐feedback involved in the regulation of nitrogenase activity in Medicago truncatula?

To determine whether senescing leaves provoke an active nitrogen (N) remobilization that results in the reduction of nitrogenase activity, 60% of Medicago truncatula lower leaves were either darkened or individually excised for two weeks. Although a considerable amount of N was remobilized, N₂ fixation activity was found to be increased to maintain the N source/sink balance, indicating an absence of the negative N‐feedback regulation of nitrogenase activity in the senescing M. truncatula.     

杀青方式对机采绿茶理化品质的影响

为了提高茶树机采绿茶杀青品质,以机采鲜叶为原料,比较微波、汽热、电热滚筒和电磁滚筒耦合热风4种杀青方式所制机采绿茶的感官品质、茶叶内含成分、色泽和香气。结果显示：电磁滚筒耦合热风杀青所制绿茶的感官得分（89分）最高,所制干茶的色相值（a/b）相对更绿（p<0.01）,酚氨比较低（p<0.05）,非酯型儿茶素、酯型儿茶素和儿茶素总量也相对较低（p<0.01）;电磁滚筒杀青所制绿茶的栗香型成分含量较高,如藏红花醛、癸醛、β-环柠檬醛、庚醛和3,7-二甲基-2,6-二辛烯醛等高级醛类,香叶基丙酮、β-紫罗酮和1-戊烯-3-酮,反式-2-辛烯醇、芳樟醇、反式-橙花叔醇等,以及二甲硫、2-甲基呋喃和1-乙基吡咯等杂环化合物,说明电磁滚筒耦合热风杀青集成了不同工艺特点,所制机采绿茶滋味鲜爽,栗香明显,该工艺有利于提高机采绿茶品质,对实际生产具有指导作用。     

Relay-intercropping soybean with maize maintains soil fertility and increases nitrogen recovery efficiency by reducing nitrogen input

Optimized nitrogen(N)management can increase N-use efficiency in intercropping systems.Legume-nonlegume intercropping systems can reduce N input by exploiting biological N fixation by legumes.Measurement of N utilization can help in dissecting the mechanisms underlying N uptake and utilization in legume-nonlegume intercropping systems.An experiment was performed with three planting patterns:monoculture maize(MM),monoculture soybean(SS),and maize-soybean relay intercropping(IMS),and three N application levels:zero N(NN),reduced N(RN),and conventional N(CN)to investigate crop N uptake and utilization characteristics.N recovery efficiency and 15N recovery rate of crops were higher under RN than under CN,and those under RN were higher under intercropping than under the corresponding monocultures.Compared with MM,IMS showed a lower soil N-dependent rate(SNDR)in 2012.However,the SNDR of MM rapidly declined from 86.8%in 2012 to 49.4%in 2014,whereas that of IMS declined slowly from 75.4%in 2012 to 69.4%in 2014.The interspecific N competition rate(NCRms)was higher under RN than under CN,and increased yearly.Soybean nodule dry weight and nitrogenase activities were respectively 34.2%and 12.5%higher under intercropping than in monoculture at the beginning seed stage.The amount(Ndfa)and ratio(%Ndfa)of soybean N2 fixation were significantly greater under IS than under SS.In conclusion,N fertilizer was more efficiently used under RN than under CN;in particular,the relay intercropping system promoted N fertilizer utilization in comparison with the corresponding monocultures.An intercropping system helps to maintain soil fertility because interspecific N competition promotes biological N fixation by soybean by reducing N input.Thus,a maize-soybean relay intercropping system with reduced N application is sustainable and environmentally friendly.     

过滤后养猪废水厌氧发酵与固氮技术研究

为探究养殖废水高效处理方法,文章采用粉碎玉米秸秆过滤养殖废水中悬浮性固体,并对过滤后养猪废水作厌氧发酵和固氮研究。经过滤,总固体(TS)去除率达47.55%,在中温(35±2)℃条件下,研究5、15、25 d 3种不同水力停留时间(HRT),过滤后养猪废水全混合厌氧发酵特性。厌氧发酵过程运行稳定,产生沼气甲烷含量均稳定在70%左右,当水力停留时间为15 d时,产甲烷效率为239.17 mL CH4/gVS,溶解性化学需氧量(SCOD)去除率60.94%。沼液采用鸟粪石沉淀法固氮处理,经过试验参数优化在物质的量比n(Mg2+)n(PO43-):n(NH4+)=1.021.061、pH为9.6条件下,氨氮(TAN)去除率达86.66%,处理后沼液中氨氮浓度为160 mg·L-1,研究结果可为养猪废水资源化利用提供参考。     

Surgical treatment of a complicated distal tibia epiphyseal Salter–Harris type I fracture in a yearling

This article describes the management of a complicated distal epiphyseal Salter–Harris type I fracture of the left tibia in a yearling horse. Closed reduction and internal fixation was attempted in the first surgery using tension band wires. Due to fracture instability 2 weeks after surgery, a full-limb transfixation pin cast was applied to the tibia and maintained for 7 weeks to prevent further fracture displacement and to achieve axial alignment. The full-limb cast was maintained for a total of 12 weeks, including the time with the transfixation pin cast. Cast sores and tendon laxity resolved without further complications. Ten months after the first surgery, the fracture had radiographically healed, and the horse was sound at the walk and trot in a straight line.     

接种根瘤菌对西南地区大豆光合性能和固氮能力的影响

为探讨接种根瘤菌对西南地区大豆固氮能力的有效性，在大田试验条件下，以根瘤菌株 Bradyrhizobium japonicum5038和B. japonicum 5136侵染南黑豆20和南夏豆25，比较两个大豆品种接种后植株的光合特性和叶绿素 含量，考察根瘤数量并测定分析其蔗糖含量、豆血红蛋白含量和固氮酶活性。结果表明：接种后两大豆品种叶片 chla/b值显著下降，叶绿素含量、净光合速率和气孔导度显著增加；根瘤数、单株瘤重、植株地上部和地下部生物量 均显著增加，单个瘤重和根冠比则无显著变化；根瘤内蔗糖含量和豆血红蛋白含量均显著增加，固氮酶活性提高。 不同大豆品种对不同菌株的响应不同，南夏豆25与根瘤菌B.japonicum5136的适配性最好，接种后大豆光合性能和 固氮能力的改善效果明显优于南黑豆20。     

供磷水平对‘热研5号'柱花草-根瘤菌共生体系的影响

为研究不同供磷水平对热研5号柱花草(Stylosanthes guianensis‘Reyan No.5')-根瘤菌共生体系的影响,利用水培试验对接种7株不同根瘤菌的柱花草进行3个磷浓度的处理,通过对柱花草干重、植株含氮量、根瘤数、固氮酶活性的测定及分析确定磷对共生体系的影响。结果表明:低磷不利于柱花草及根瘤菌共生体系的生长;菌株YM11-1,FS3-1-1在高磷时固氮促生效果最佳,菌株LZ3 2,RJS9-2,BS1-1,CJ1则在中等磷条件下固氮促生效果最佳,磷对菌株PN13-3的影响不大。     

沙漠藻固沙结皮的研究与问题探讨

本文综合分析了沙漠藻结皮研究的现状,并结合自己的研究,探讨了沙漠藻固沙结皮的形成与植被发育的关系、沙漠藻结皮人工接种效果,提出了藻沙粒结皮是沙漠藻结皮的早期形式,探讨了进一步研究沙漠藻固沙结皮的关键技术问题。