DIFFUSION THROUGH STOMATES

Ting, Irwin P., and Walter E. Loomis. (Iowa State U., Ames.) Diffusion through stomates. Amer. Jour. Bot. 50(9): 866–872. Illus. 1963.—It is shown that the rule that diffusion through isolated, small pores is proportional to the diameter rather than the area of the pores is valid for pores of diameters as small as 20 μ, and that the curve extends to the origin at zero diameters, indicating that the law is effective throughout the range of stomatal sizes. Suggestions that an elliptical pore will be relatively more effective in diffusion than a circular one and that diffusion is concentrated at the periphery of the pore are not supported by experimental evidence and are physically improbable. Brown and Escombe's conclusion that there is no interference in the diffusion through the individual pores of a multiperforate membrane if the pores are spaced 10 diameters apart is not valid for diffusion through the stomates of a leaf. With pores of 200 μ and less spaced 10 diameters apart, interference increases rapidly with a smaller size and larger number of pores. As a result, the diffusion through a membrane with pores 19 μ in diameter and 190 μ apart was the same as that through a membrane with pores 132 μ in diameter and 1.32 mm apart, although the calculated capacity of the first membrane was 7 times that of the second. The diffusion of water vapor through multiperforate membranes with pores spaced 10 diameters apart has an apparent maximum of 65–70% of the diffusion through an open tube. Calculations of the effect of partial closing of stomates, using Verduin's equation for interference between pores, indicate that the theoretical diffusion capacity of 10 μ stomates spaced at 10 diameters would be increased several times by closing to an average diameter of 5 μ. This increase illustrates the dominant effect of interference in diffusion through small, closely spaced pores. Calculated diffusion through these stomates would not be decreased until they were more than 95% closed. It is concluded that stomatal opening will have no important effect on diffusion from or into a leaf until the stomates are essentially closed.     

ULTRAFILTRATION THROUGH COLLODION MEMBRANES

It is obvious that the factors considered in this paper render data obtained by ultrafiltration open to criticism unless they are checked by other methods and precautions are taken for the elimination of the vitiating effects which have been described. As regards the mechanism of ultrafiltration, the view of a sieve-like action as most experimental evidence indicates, is adequate, if all the factors are considered which might modify the effective pore size. The behaviors of collodion membranes which seem contrary to a mechanism of ultrafiltration based on the existence of a system of pores, can be explained on the basis of a variable layer of adsorbed fluid on the walls of the pores. It is, therefore, unsound to make any deductions about living tissues from the demonstration of changes produced in the behavior of collodion membranes. Thus, the increase in the rate of filtration of water through collodion by diuretics (29) or the change of permeability due to the presence of surface-active materials, gives us no information about their action in the living organism. The effect of these substances on a sieve-like membrane of the type of collodion would not necessarily bear any analogy to that exerted on the emulsion type of membrane of living cells. The mechanisms of the reactions necessary to produce the same effects in such widely differing systems may be entirely unrelated.     

SPRING MIGRATION THROUGH SOUTHEAST MOROCCO

Very few quantitative data existed for the spring migration of birds across the Sahara desert. Observations covering 105 days in spring 1963–66 were made at Defilia, on the extreme northern fringe of the desert in southeast Morocco. The physical features and climate of the area are described, with brief reference to neighbouring desert zones. The birds recorded are listed in weekly or part-weekly totals, followed by subspecific and other comments on selected species.
The movements of migrants are summarized, together with the effects of adverse winds on migration; very bad weather along the northern desert fringe may contribute to the late arrival of some species in the British Isles (and presumably elsewhere in Europe) in spring by causing delays and heavy mortality. Most visible migration was northeastward or eastward, but substantial westward movements of hirundines took place.
Comparison is made with migration through other areas in Morocco and Algeria, both from existing literature and from previously unpublished data, which provide evidence of broad-front migration across the entire width of the Moroccan Sahara. Birds recorded in northwest Algeria in 1966 are listed, together with notes on physical features, climate and field observations. Many terns and waders were recorded at Daiat Tchiour, including some predominantly coastal species, which suggests that the latter were migrating on a great-circle track from winter quarters in West Africa across the Sahara to their breeding grounds in Siberia.
Recoveries of ringed birds are discussed; some of these, together with records of species well west of their normal migratory range, suggest that birds may be subject to lateral displacement by winds when crossing the Sahara, leading to considerable annual variation in species and numbers of birds recorded on the northern desert edge, even in the same place.     

CARDIAC RESUSCITATION THROUGH THE INTACT CHEST

External cardiac compression and external defibrillation were successful in resuscitating 27 consecutive dogs after the production of ventricular fibrillation. Twelve patients survived following circulatory arrest treated with closed chest cardiac compression and, when indicated, defibrillation. Five additional patients were successfully resuscitated but died in the hospital. In fifteen cases, resuscitation was not successful.     

MACROEVOLUTION AND MACROECOLOGY THROUGH DEEP TIME

Abstract:  The fossil record documents two mutually exclusive macroevolutionary modes separated by the transitional Ediacaran Period. Despite the early appearance of crown eukaryotes and an at least partially oxygenated atmosphere, the pre-Ediacaran biosphere was populated almost exclusively by microscopic organisms exhibiting low diversity, no biogeographical partitioning and profound morphological/evolutionary stasis. By contrast, the post-Ediacaran biosphere is characterized by large diverse organisms, bioprovinciality and conspicuously dynamic macroevolution. The difference can be understood in terms of the unique escalatory coevolution accompanying the early Ediacaran introduction of eumetazoans, followed by their early Cambrian (Tommotian) expansion into the pelagic realm. Eumetazoans reinvented the rules of macroecology through their invention of multitrophic food webs, large body size, life-history trade-offs, ecological succession, biogeography, major increases in standing biomass, eukaryote-dominated phytoplankton and the potential for mass extinction. Both the pre-Ediacaran and the post-Ediacaran biospheres were inherently stable, but the former derived from the simplicity of superabundant microbes exposed to essentially static, physical environments, whereas the latter is based on eumetazoan-induced diversity and dynamic, biological environments. The c . 100-myr Ediacaran transition (extending to the base of the Tommotian) can be defined on evolutionary criteria, and might usefully be incorporated into the Phanerozoic.     

DIAPHRAGMATIC HERNIATION THROUGH THE SPACE OF MORGAGNI

In most cases diaphragmatic herniation through the space of Morgagni is asymptomatic and is first noted in routine roentgenograms of the chest. The diagnosis must be considered when shadows are seen in the anterior cardiodiaphragmatic angle. Lateral views are valuable in localizing the lesion. Simple procedures such as pneumoperitoneum should be used in differential diagnosis but when the diagnosis cannot be established by these simpler means exploratory thoracotomy is indicated, because of the possibility of carcinoma of the middle lobe of the lung.If diagnosis is established, thoracotomy is indicated as an elective procedure for repair of the defect, which may have serious consequences.Nine cases of diaphragmatic herniation through the space of Morgagni are summarized and a case report is included which illustrates the potential danger of this condition.     

物质经皮转运的唯象理论

物质经皮渗透是一个非平衡态的热力学过程,驱使物质经皮转运的动力产生了物质经皮转运的通量,文章试图用唯象理论来阐述这种关系。假设扩散池系统恒温、无化学反应：溶液为非粘性流体,双组份、局域平衡。根据Gibbs方程,建立了扩散池系统的耗散函数,导出了其质量流与质量力、体积流与体积力：实验分对照组(被动扩散)和实验组(电脉冲扩散),分别做3次并以替硝唑为模式药物。实验结果表明：(1)扩散池系统中不但存在物质的经皮渗透,而且存在溶液的体积缺失现象;(2)根据实验数据,确定唯象系数具有时变性,并且推断当时间延迟时,质量力对质量流和体积力对体积流的影响减弱;(3)溶液对流在皮肤表面产生的速度梯度可能产生体积流。结论是扩散池药物经皮渗透系统是一个非线性时变系统。     

通过交配系统了解植物生殖生态学

进行有性生殖的植物可以通过两个途径——花粉或者种子——来传递它们的基因 (即适合度 )。雌雄同体的植物不仅可以依靠种子生产获得雌性适合度 ,而且还可以依靠花粉途径获得雄性适合度。从种群角度看 ,这两个途径完全是均等的 ,在重要性上并没有什么差别。每个二倍体生物都只有一个父亲、一个母亲。对于一个繁育种群来说 ,通过种子途径传递的基因与通过花粉途径传递的基因在数量上必然是相等的 ,虽然不同个体之间可能存在着这样或那样的差别。早期的植物学家几乎把注意力全部集中在种子生产上 ,基本上忽略了植物个体的雄性适合度组分 ,似乎…     

原生质体融合提高农抗武夷菌素的效价

从农抗武夷菌素产生菌不吸水链霉菌武夷变种菌株Co-N-31诱变获得两个突变株M35(Leu^-,孢子颜色灰色)和M46(ser^-.孢子颜色灰白色),并以此两突变株为直接亲本在25％ PEG1000诱导下进行种内原生质体融合。M35和M46原生质体再生率分别为3.72％和0.248％,重组频率为55.20％。采用间接法选择营养标记互补的稳定的原养型重组子,并从中获得一株高产菌株F31-24;其效价比原始亲本Co-N-31提高了82％。薄层层析结果表明,菌株F31-24和Co-N-31的发效产物在Rf值为0.50和0.26处均有斑点,但含量有异。测定斑点生物活性证明其均有抑菌活性。温室试验表明,菌株F31-24发酵产物对小麦白粉病的防治效果优于菌株Co-N-31。