Atmospheric ammonia: absorption by plant leaves

By monitoring the disappearance of ammonia from an airstream flowing through a small growth chamber containing a single plant seedling, it was discovered that plant leaves absorb significant quantities of ammonia from the air, even at naturally occurring low atmospheric concentrations. The measured absorption rates of ammonia showed large diurnal fluctuations and varied somewhat among species, but differed little with the nitrogen fertility level of plants within a species.     

Solar nitrogen: evidence for a secular increase in the ratio of nitrogen-15 to nitrogen-14

Solar wind nitrogen, implanted in lunar soil samples, exhibits isotopic variations that are related to the time, although not to the duration, of implantation, with earlier samples characterized by lower ratios of nitrogen-15 to nitrogen-14. An increase in the solar nitrogen-15 content during the lifetime of the lunar regolith is probably caused by spallation of oxygen-16 in the surface regions of the sun.     

Light-enhanced potassium absorption by corn leaf tissue

The rate of absorption of potassium by slices of corn leaf in the light was about twice the rate in the dark. When the light was turned on or off, changes in the rate of absorption took place some minutes after the change in illumination. Experiments with the antimetabolites, 2,4-dinitrophenol and cyanide, indicated that the source of energy for active accumulation of potassium by green tissue in the light was different from that in the dark. In the light, energy was closely linked to photosynthetic reactions; in the dark, it was linked to respiratory processes.     

改性竹炭对氨氮的吸附性能研究

利用硝酸对竹炭进行改性,以提高其吸附能力.研究竹炭投加量、吸附时间、吸附温度、pH等因素对改性竹炭吸附氨氮的影响,并初步探讨竹炭吸附氨氮的机理.实验表明:竹炭的表面化学性质和表面结构特性分别影响其化学吸附能力和物理吸附能力.改性竹炭相对于未改性竹炭,其表面酸性含氧官能团量G、比表面积S、孔比容积Vp明显增大,氨氮的最高吸附去除率由20.1%提高至82.2%,吸附平衡时间由未改性时的6 h缩短至4 h.氨氮在竹炭上的吸附等温方程可与Freundlich模型较好拟合.竹炭投加量、吸附时间、吸附温度、pH 等因素对改性竹炭吸附能力有明显影响.     

不同丛枝菌根真菌对甜玉米幼苗生长及氮磷吸收的影响

为了探究不同丛枝菌根真菌对甜玉米（Zea mays var. rugose Bonaf.）生长及氮磷吸收的影响,筛选出促进甜玉米生长和氮磷吸收的优良菌种,采用盆栽培养方法,以甜玉米（Zea mays var. rugose Bonaf.）为宿主植物,研究接种摩西斗管囊霉（Funneliformis mosseae, Fm）、球状巨孢囊霉（Gigaspora margarita, Gm）、细凹无梗囊霉（Acaulospora scrobiculata, As）、扭形伞房球囊霉（Corymbiglomus tortuosum, Ct）、地表多样孢囊霉（Diversispora epigaea, De）和根内根孢囊霉(Rhizophagus intraradices, Ri)对甜玉米生长及氮磷吸收的影响。结果表明：接种De处理的甜玉米株高、根长、地上部鲜质量、地上部生物量和磷积累量最高,并显著高于其他处理,其茎粗和地上部氮积累量也达到较高的水平;且主成分分析结果表明,甜玉米接种De菌种综合表现最好。因此,在田间种植甜玉米时,推荐接种De菌种,从而更有利于甜玉米的生长和氮磷养分积累。     

Nitrogen enrichment of surface water by absorption of ammonia volatilized from cattle feedlots

Apparatus designed to measure absorption of ammonia from the air by aqueous surfaces was installed near several cattle feedlots and in appropriate control areas. Ammonia absorption rates measured near feedlots were as much as 20 times greater than near the control. Their magnitudes indicate that absorption of ammonia volatilized from cattle feedlots contributes significantly to the nitrogen enrichment of surface water in the vicinity of feedlots.     

Translocation and recovery of 15N-labeled N derived from the foliar uptake of 15NH3 by the greenhouse tomato (Lycopersicon esculentum Mill.)

In order to completely evaluate ammonia emission from greenhouse vegetable fields, crop canopy absorption should not be neglected. The foliar uptake of NH₃ applied at two growth stages and the subsequent ¹⁵N-labeled N translocation to other plant components were investigated under greenhouse conditions using chambers covered with the soil of a tomato field. Treatments comprised three NH₃-N application rates (70, 140, and 210 mg/plot) using ¹⁵N-labeled ammonium sulfate. Plants were harvested immediately after exposure for 24 h, and the total N concentrations and ¹⁵N/¹⁴N ratios were determined. With increased NH₃ concentration, total ¹⁵NH₃-N absorption increased considerably, whereas the applied ¹⁵NH₃-N uptake decreased gradually. The tomato plants absorbed 33–38% and 24–31% of the ¹⁵NH₃-N generated at the anthesis and fruit growth stages, respectively. A total of 71–80% of the recovered NH₃ was observed in the leaves and 20–30% of the recovered NH₃ was remobilized to other components. Among them, an average of 10% of the absorbed ¹⁵NH₃-N was transferred into the tomato fruits. All these results indicated the potential of the tested tomatoes for the foliar uptake of atmospheric ¹⁵NH₃ and the distribution of ¹⁵N-labeled vegetative N among different plant components. The results are of great importance for the complete evaluation of nitrogen use efficiency in the greenhouse tomato fields.     

EDTA对桑树和任豆幼苗吸收重金属Pb的影响

【目的】研究不同重金属Pb2＋浓度下螯合剂EDTA处理对桑树和任豆幼苗修复土壤中重金属Pb2＋的效果及Pb2＋在植物茎叶及根部积累,以期为重金属污染土壤生态修复及植物资源的合理利用提供理论依据。【方法】用盆栽模拟法,以4L／盆Hoagland营养液作为培养液,培养液中的Pb2＋浓度分别为0、2．5、5．0、10．0、25．0、50．0、100．0、150．0、200．0、250．0mg／L,EDTA的浓度均为0．55mmol／L,以不添加EDTA作对照。分别测定桑苗和任豆幼苗茎叶和根部的Pb2＋浓度。【结果】随着水培液中Pb2＋浓度的增加,桑树和任豆幼苗对Pb2＋的吸收和积累量也逐渐增大;在相同的重金属Pb2＋胁迫背景下,加入EDTA的桑树和任豆幼苗对Pb2＋的吸收量比不添加EDTA的对照组明显增高;桑树和任豆幼苗体内Pb2＋浓度通常为根部〉茎叶,而添加EDTA能加速重金属Pb2＋向茎叶的转运。随着培养液中Pb2＋浓度的增加和时间的延长,Pb2＋在植物根部的积累逐渐增加,而向茎叶的转运则相对减少。【结论】桑树和任豆幼苗具有较强的重金属Pb耐性,而EDTA能促进桑树和任豆幼苗对重金属Pb2＋的吸收,因此,桑树和任豆可作为修复植物应用于重金属污染地区。     

应用~(15)N示踪研究毛白杨苗木对不同形态氮素的吸收及分配

为探讨毛白杨苗木对不同形态氮素的吸收、分配及利用特性,以毛白杨新无性系83号插条苗为试材,于2007年3—9月在北京林业大学苗圃,应用15N示踪技术测定在相同施氮量下毛白杨苗木对硝态氮(NO3-15N)和铵态氮(NH4-15N)的吸收率、利用率及分配率等指标。结果表明:①施肥后28 d,苗木对两种氮肥的吸收利用达到最大值,其中,标记NO3-15N肥吸收率为0.36 g/株,利用率达35.98%;标记NH4-15N肥吸收率为0.15 g/株,利用率为14.53%。②苗木NO3-15N肥平均利用率(19.75%)约为NH4-15N肥(7.95%)的2.5倍。③施肥后各个时期,全株的NO3-15N肥Ndff值均显著大于NH4-15N肥。各器官对NO3-15N肥的征调能力明显高于NH4-15N肥,茎对肥料征调的竞争能力最强,其次为叶和根。④氮素分配率在各器官中差异显著(P<0.05),总体趋势为叶>根>茎。叶中NO3-15N的分配率均高于NH4-15N,根中储存的氮素主要供地上部分生长所需,总体呈逐渐下降的趋势,茎是氮素贮藏的"临时库",苗木主要通过茎将吸收的氮素输送到叶等生长旺盛的部位。     

Tobacco seedlings: damage by excessive nitrogen lessened by added phosphorus

Concentrations of nitrogen (as ammonium nitrate) of 50 kilo-grams per hectare and greater are toxic to tobacco seedlings; symptoms are poor growth and white leaves. The leaves have markedly less chlorophylls (especially chlorophyll a) and more carotene and xanthophyll than seedlings grown in media low in nitrogen. These ill eflects are aggravated by short supply of phosphorus; they can be counteracted by more liberal supply of phosphorus.     

不同配施菌糠肥料对污灌区玉米 Cu、Pb、Cr 吸收及转移的影响

采用盆栽试验,研究不同配施菌糠肥料对污灌区土壤种植玉米生长发育及不同部位(根、茎、叶、穗)中重金属元素(Cu、Pb、Cr)吸收与转移的影响。结果表明:(1)与未配施菌糠处理相比,施用不同配施菌糠肥料后,玉米各部位干重及株高均有所增加。(2)玉米地下部Cu、Pb含量平均增加11.20%、17.12%,Cr含量平均减少24.13%;地上部Cu、Pb含量减少;叶片Cr含量增加。(3)玉米对Cu的转移系数、富集系数降低,且均小于1;对Pb的转移系数、富集系数降低,其中对Pb的转移系数大于1;对Cr的转移系数、富集系数整体呈增加趋势,且转移系数大于1。说明施用不同配施菌糠肥料可有效降低玉米对Cu、Pb、Cr3种重金属的吸收,同时降低Cu、Pb元素向地上部的转移率,将由地下部转移到地上部的Cr元素固定在玉米叶中,降低其他部位的Cr元素含量。     

Geotropism in corn roots: evidence for its mediation by differential Acid efflux

The elongation zone in intact growing corn roots secretes acid leading to a reduced pH along the surface of the root and in the adjacent medium. This can be detected by placing the root on an agar medium containing the pH indicator dye bromocresol purple. When the root is treated with a growth inhibitory concentration of the hormone indole-3-acetic acid, the acid efflux is reversed and growth is greatly retarded. When the root is mounted vertically, acid secretion is uniform along the elongation zone, and the root grows straight downward. When the root is placed horizontally, there is enhanced acid efflux along the upper surface of the elongation zone and reduced acid efflux along the lower surface. An increased rate of elongation of the upper cells relative to the lower cells then results in downward curvature of the root. The correlation between acid efflux patterns and growth patterns indicates that proton efflux is important in the control of root growth.     

Selective photothermolysis: precise microsurgery by selective absorption of pulsed radiation

Suitably brief pulses of selectively absorbed optical radiation can cause selective damage to pigmented structures, cells, and organelles in vivo. Precise aiming is unnecessary in this unique form of radiation injury because inherent optical and thermal properties provide target selectivity. A simple, predictive model is presented. Selective damage to cutaneous microvessels and to melanosomes within melanocytes is shown after 577-nanometer (3 x 10(-7) second) and 351-nanometer (2 x 10(-8) second) pulses, respectively. Hemodynamic, histological, and ultrastructural responses are discussed.     

Soot in urban atmospheres: determination by an optical absorption technique

We have used the high optical absorptivity of urban and source particulates to trace their "graphitic" component. The optical absorptivity and the particulate carbon loading show a strong correlation. Analyses of the data indicate that primary soot emissions compose a major fraction of the carbonaceous aerosol and put a low limit on secondary organic material produced in correlation with the ozone concentration.     

Ion pairing of magnesium sulfate in seawater: determined by ultrasonic absorption

Data from ultrasonic absorption in synthetic and natural seawater can be used to calculate pairing of magnesium and sulfate ions in seawater. Calculation under the assumption that data from ion pairing in single salt solution can be applied to seawater solution results in a value of 9.2 percent for the amount of magnesium paired with sulfate and 17.5 percent for sulfate paired with magnesium.     

Virus-induced murine leukemia: its inhibition and suppression by serum containing erythropoietin

Mice infected at 2 days of age with a virus that induces reticulum cell sarcoma and myeloerythroleukemia were treated with erythropoietin-containing serum obtained from rabbits that had been treated with acetylphenylhydrazine. A marked inhibition of tumor induction occurred, particularly in females, when treatment was begun early. Delayed treatment resulted in instances of regression of overt neoplasia.     

Inhibitory oxidation products of indole-3-acetic acid: enzymic formation and detoxification by pea seedlings

Extracts of etiolated pea seedlings oxidize indole-3-acetic acid, a plant auxin, to 3-hydroxymethyloxindole. At physiological pH this compound is dehydrated to 3-methyleneoxindole, a highly reactive sulfhydryl reagent and inhibitor of cell growth. 3-Methlyeneoxindole is in turn detoxified by an enzymatic, triphosphopyridine nucleotide-linked reduction to 3-methyloxindole, a nontoxic compound. These enzymatic conversions may be responsible for some of the responses to auxin, particularly sensitivity to its inhibitory effects on growth.     

Mechanism of ammonia transport by Amt/MEP/Rh: structure of AmtB at 1.35 A

The first structure of an ammonia channel from the Amt/MEP/Rh protein superfamily, determined to 1.35 angstrom resolution, shows it to be a channel that spans the membrane 11 times. Two structurally similar halves span the membrane with opposite polarity. Structures with and without ammonia or methyl ammonia show a vestibule that recruits NH4+/NH3, a binding site for NH4+, and a 20 angstrom-long hydrophobic channel that lowers the NH4+ pKa to below 6 and conducts NH3. Favorable interactions for NH3 are seen within the channel and use conserved histidines. Reconstitution of AmtB into vesicles shows that AmtB conducts uncharged NH3.     

Aromatic cross-links in insect cuticle: detection by solid-state 13C and 15N NMR

Cross-polarization magic-angle-spinning nuclear magnetic resonance spectroscopy has been used to determine insect cuticle composition and cross-link structure during sclerotization or tanning. Unsclerotized cuticle from newly ecdysed pupae of the tobacco hornworm, Manduca sexta L., had a high protein content with lesser amounts of lipid and chitin. Concentrations of chitin, protein, and catechol increased substantially as dehydration and sclerotization progressed. Analysis of intact cuticle specifically labeled with carbon-13 and nitrogen-15 revealed direct covalent linkages between ring nitrogens of protein histidyl residues and ring carbons derived from the catecholamine dopamine. This carbon-nitrogen adduct was present in chitin isolated from cuticle by alkaline extraction and is probably bound covalently to chitin. These data support the hypothesis that the stiffening of insect cuticle during sclerotization results primarily from the deposition of protein and chitin polymers and their crosslinking by quinonoid derivatives of catecholamines.     

Air pollution: sensitive detection of ten pollutant gases by carbon monoxide and carbon dioxide lasers

Detection sensitivities of a few parts per billion for ten gaseous pollutants have been evaluated by measuring the strength of the absorption of infrared radiation from carbon monoxide and carbon dioxide lasers. Ethylene concentrations as small as 5 parts per billion have been detected in air. The measured absorption strengths indicate that in mixtures of pollutants, such as nitrogen dioxide and water vapor, the sensitivity is reduced by overlapping absorption bands. However, calculations indicate that it should be possible to detect nitrogen dioxide concentrations of 0.01 part per million in the presence of water vapor concentrations of 105 parts per million.