Selective plant growth suppression by shoot application of soil bacteria

Selected rhizosphere bacterial isolates, previously determined as plant growth deleterious, were tested for their ability to suppress plant growth after foliar spray applications, for selectivity with regard to plant species, and in pilot field experiments for their potential as weed biocontrol agents. Inundative foliar applications of aqueous bacterial suspension were performed on a range of weed and crop species. Plant symptoms after spraying ranged from rapid necrosis and wilting to an overall growth suppression or stunting. Significant and selective reductions in biomass of up to 90% fresh weight, as well as large reductions in plant survival and plant height were recorded in greenhouse pot experiments. However, monocotyledonous plants were affected weakly or not at all by two isolates extensively tested. Effects of these were dose- and plant age-dependent, and were for some plants enhanced by high relative humidity. For one isolate, A153, effects were also expressed in cell-free culture filtrates pointing to involvement of specific metabolites. In pilot field experiments, strong growth suppression was observed on broad-leaved plants, while barley crop plants were unaffected.     

The extent of representation,the relationships of artifacts and the anthropology of art

This paper provides an account of the potential roles that artifacts can occupy and distinguishes their occurrence as instruments of representation from other types of relationship of artifact use. When artifacts are employed as instruments of representation there is a deliberately constructed causal connection between the artifact and what it represents. This is in contrast to relationships of association in which the artifact takes on features of the context of its occurrence. Anthropological studies of artifact use in the native societies of Africa, America, the Indian Subcontinent and the Pacific are reviewed by comparing “dominant functions” that artifacts can serve.     

The Reissner's Fiber Termination in Some Lower Chordates

The caudal end of the neural tube of the tunicate Oikopleura, the cephalochordate Branchiostoma and newly hatched fry of the clupeiform teleosts Clupea, Engraulis and Sardinops was studied by means of the electron microscope. In Oikopleura and the teleost larvae either Reissner's fiber or an amorphous mass of fiber substance leaks out of the neural tube into the surrounding tissue spaces. In Branchiostoma the disintegrated fiber material is apparently engulfed by the caudal ependymal cells. A relationship seems to exist between the degree of fiber disintegration within the neural tube and the degree of specialization of the caudal neural tube ependymal cells, the two extremes being represented by Branchiostoma with a “closed” Reissner's fiber system with highly specialized caudal ependymal cells and a teleost fry with the intact fiber leaving the neural tube between almost undifferentiated ependymal cells. These observations on lower chordates are in accordance with the hypothesis that Reissner's fiber acts as a detoxicator for the neural tube fluid.     

A sensitive method for measuring oxygen consumption

A technique is presented whereby oxygen consumption rates of the order of 10⁻⁶ μl/hr can be measured, thus providing a means for studying the respiration rates of single cells, even slowly respiring ones. The technique is based on the principle of incubating cells in extremely small chambers containing highly concentrated hemoglobin solutions. The absorbance shift occurring when hemoglobin is transformed from its oxygenated to its deoxygenated form is recorded microspectrophotometrically. The results obtained by this technique seem to be well in accordance with those of the Warburg manometric method. The technique is convenient and easy to handle and the sensitivity can be varied within wide limits, permitting different types of materials to be studied. In experiments using yeast cells, respiration rates from 1.0 × 10⁻⁶ to 1.8 × 10⁻⁶ μl O₂/cell/hr were revealed.     

Free radicals in malonic acid: A study of radical conformations at 77 K and 295 K by the ESR-technique

Summary Single crystals of malonic acid (CH₂(COOH)₂), have been irradiated with 4.0MeV electrons at liquid nitrogen temperature. The induced radicals have been identified by electron spin resonance technique. ESR lines due to different conformations of the H₂(COOH) radical are observed. ESR lines due to the OOH radical are also seen. It is suggested that the fragmentation into these radicals takes place preferentially on one side of the molecule and subsequent to the ionization event. Upon warming of the crystal to room temperature, the OOH radical disappears and the H(COOH)₂ radical is formed. The latter radical seems to exist in two slightly different modifications.     

Comparative study of some haematological and biochemical blood parameters in fishes from the Skagerrak

Marine fishes caught in the Skagerrak, 27 different species representing various groups of fishes (Cyclostomi, Holocephali, Elasmobranchii and Teleostei), were examined for the following haematological and biochemical blood parameters: haematocrit, haemoglobin, mean corpuscle haemoglobin concentration, total plasma protein, blood glucose and blood lactate. Interspecies variations as well as variations within some species were observed. The haemoglobin values for all species showed a positive correlation to the corresponding haematocrit values. Relatively low values for haematocrit and haemoglobin were found in cyclostomes, holocephaleans and elasmobranchii compared to the majority of teleosts. Within the teleost group, the haematocrit and haemoglobin levels were positively correlated with the activity of the fish species. The cyclostome Myxine glutimsa L. had a total plasma protein content in the same range as most teleosts, whereas holocephaleans, elasmobranchii and the deep-water teleost Coryphaenoides rupestris Gunnerus showed comparatively low values. Among teleosts some relationship seemed to exist between the total plasma protein level and the activity of the fish species. In addition, a correlation between plasma protein content and levels of blood lipids were noted. Values for blood glucose and blood lactate were found to be lower in cyclostomes, holocephaleans and elasmobranchii than in most teleosts. Higher blood glucose levels were observed in the more active teleost species.     

Nerve-purkinje fiber relationship in the moderator band of bovine and caprine heart

Summary The moderator band in the heart of the ox and goat contains bundles of Purkinje fibers and nerve fibers separated by connective tissue. The axons are mostly unmyelinated and embedded in the cytoplasm of Schwann cells.Small bundles of axons run close to the Purkinje fibers. The axons dilate into varicosities 0.5 to 1.6 in diameter (mean 0.95 ), containing three types of vesicles: 1) agranular vesicles with a diameter of 400–500 Å, 2) large dense-cored vesicles with a diameter of 800–1200 Å, 3) small dense-cored vesicles with a diameter of 500 Å. Most varicosities contain agranular vesicles together with a few large dense-cored vesicles.The gap between the varicosities and the nearest Purkinje fiber is unusually wide and normally varies between 0.3 and 0.8 . No intimate nerve-Purkinje fiber contacts, with a cleft of 200 Å, were observed.     

The Wheel Organ and Hatschek's Groove in the Lancelet,Branchiostoma lanceolatum (Cephalochordata)

The wheel organ is a specialized epithelium in the roof and sides of the adult lancelet oral cavity. It borders the oral epithelium proper, separated by a thin strip of margin cells which are not ciliated but contain a few large dense-cored vesicles apically. The wheel organ cells are tall and strongly ciliated and have dark, heterochromatin-rich nuclei. Dorsally, and slightly paramedially, the organ is further specialized, forming the so-called Hatschek's groove (pit), which consists of two ciliated cell types. The first type synthesizes a dense granular material, the granules being approximately 95 nm in diameter. This is stored basally and apparently it is also released through the basal cell membrane into the blood cavities. The cells at the bottom of Hatschek's groove have peculiar rod-shaped apical cellular regions. Each cell bears one tall cilium surrounded by microvilli and it is apparently involved in the production of secretory material into the groove. It is evident that the histology, and probably also the function, of the wheel organ and its groove is much more complex than hitherto believed.