The kinetics of abscisic acid action on root growth and gravitropism

Using an auxanometer and time-lapse cinematography we have studied the timing of abscisic acid (ABA) effects on elongation, gravitropic curvature, and hydrogen-ion efflux in several cultivars of maize (Zea mays L.). The effect of high concentrations (e.g. 0.1 mM) of ABA on root elongation is triphasic, including 1) a period of promotion lasting approximately 12 h, 2) a subsequent period of increasing inhibition lasting approximately 12h, and 3) gradual recovery to a rate within approximately 80% of the control rate. With lower concentrations of ABA (e.g. 0.1 μM) only the transient promotive phase is seen. Abscisic acid enhances ethylene biosynthesis in roots of maize but suppression of ethylene biosynthesis does not prevent the long-term inhibitory action of ABA on growth. Application of ABA (0.1 mM) to the upper surface of horizontally placed roots accelerates positive gravitropism. Application of ABA to the lower surface retards gravitropism and in some cases causes the roots to curve upward against the direction of gravity. These observations are consistent with our finding that the initial effect of ABA on root elongation is stimulatory. Since root gravitropism is rapid enough to be completed within the stimulatory phase of ABA action, the data argue against hypotheses of gravitropism based upon accumulation of ABA to inhibitory levels on the lower side of a hirizontal root.     

Neurospora tyrosinase: structural,spectroscopic and catalytic properties

Summary Tyrosinase is a copper containing monooxygenase catalyzing the formation of melanin pigments and other polyphenolic compounds from various phenols. This review deals with the recent progress on the molecular structure of the enzyme from Neurospora crassa and the unique features of the binuclear active site copper complex involved in the activation of molecular oxygen and the binding of substrates. The results of the spectroscopic properties of Neurospora tyrosinase will also be discussed in the light of the structural similarity of the copper complex in the oxygen binding hemocyanins.     

Chemical composition and structure of cell wall teichoic acids of staphylococci

The cell wall teichoic acid structures of 22 staphylococci including 13 type strains were determined. Most of the strains contain a poly(polyolphosphate) teichoic acid with glycerol and/or ribitol as polyol component. The polyolphosphate backbone is partially substituted with various combinations of sugars and/or amino sugars. Most of the substituents occur in a monomeric form but some strains also contain dimers of N-acetylglucosamine as substituents. Staphylococcus hyicus subsp. hyicus NCTC 10350 and S. sciuri DSM 20352 revealed rather complex cell wall teichoic acids. They consist of repeating sequences of phosphate-glycerol-phosphate-N-acetylglucosamine. The amino sugar component is present in this case as a monomer or an oligomer (n less than or equal to 3). Moreover, the glycerol residues are partially substituted with N-acetylglucosamine. The cell wall teichoic acid of S. auricularis is a poly(N-acetylglucosaminyl-phosphate) polymer similar to that found in S. caseolyticus ATCC29750. The cell wall teichoic acid structures for type strains of S. auricularis, S. capitis, S. cohnii, S. haemolyticus, S. hominis, S. hyicus subsp. hyicus, S. sciuri, S. xylosus and S. warneri were determined for the first time in detail. The structures of some of the previously described teichoic acids had to be revised (S. epidermidis, S. simulans, S. aureus phage type 187).     

Morphologic der seeigelzähne II. Die gekielten Zähne der echinacea (Echinodermata,echinoidea)

Structure and growth of a keeled tooth are discussed with Paracentrotus lividus as the main example. The microscopic structure of the tooth skeletons of other sea urchins was compared, considering at least one member of each family with the exception of Saleniidae. Attention is called to the necessary revision of the system of sea urchins.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Die Ausdrucksbewegungen der Sichelente,Anas falcata L.

Zusammenfassung Die Ausdrucksbewegungen der Sichelente,Anas (Eunetta) falcata Georgi, werden beschrieben, soweit möglich vorläufig analysiert und mit denen nächstverwandter Arten, vor allem denen vonAnas (Nettium) crecca crecca L.,Anas (Chaulelasmus) strepera L. undAnas (Mareca) penelope L. verglichen. Dieser Vergleich ergibt, genau wie der morphologischer Merkmale des Gefieders und der Knochentrommel, eine systematische Stellung vonfalcata genau zwischen den drei genannten Arten, näher den beiden erstgenannten als der dritten. Die Verteilung der Merkmal-Gemeinsamkeiten einerseits mitcrecca, andererseits mitstrepera, läßt den Schluß zu, daß die drei Arten divergent aus einer gemeinsamen Ahnenform entstanden seien. Keine gemeinsamen Merkmale, die bei anderen Arten fehlen, verbinden die drei genannten Formen zu einer Gruppe.Beim Gesellschaftsspiel der Sichelerpel sind, im Gegensatz zu dem aller anderen bisher daraufhin untersuchten Schwimmentenarten, alle beteiligten Bewegungsweisen, einschließlich des einleitenden Schüttelns, zur Ente hin orientiert, die hier, wie beicrecca undstrepera, am Spiel der Erpel sehr regen Anteil nimmt. Dagegen fehlen solche Bewegungen, die durch Ritualisierung aus Angriffsverhalten entstanden sind, beim Gesellschaftsspiel völlig, spielen aber eine große Rolle, analog dem Triumphgeschrei der Gänse und Tadorninen, beim Zusammenhalt der bereits verpaarten Tiere.     

On the ultrastructure and the supposed function of the mineralizing matrix coat of sea urchins (Echinodermata,Echinoida)

Summary Echinoderm ossicles are part of the mesenchyme. Their formation and growth, with respect to the underlying tissues, is studied using echinoid spines and teeth and applying different methods of fixation. The calcification process in echinoderms is strictly intracellular and needs (1) syncytial sclerocytes which completely enclose (2) a vacuolar cavity which in turn contains (3) an organic matrix coat. Strictly speaking, each ossicle is nothing but the calcified vacuolar space of a single syncytium of sclerocytes. In fully grown parts, however, the continuous sheath may split open and the matrix-coated mineral may come into contact with the extracellular space. According to biochemical analyses the matrix consists of insoluble components, but most (95%) of its constituents are soluble in EDTA or weak acids. If routine transmission electron microscope methods are used the soluble components are lost and the matrix at best looks electron light. If tannic acid is added to the fixative the soluble matrix components are preserved and reveal further ultrastructural details of the biomineralization process in echinoderms. The matrix coat looks extremely electron dense. Further soluble material is to be found within the vacuolar space or attached to the vacuolar surface of the cytoplasmic sheath. The results lead to the opinion that the matrix coat consists of a hydrophobic framework of insoluble components that contains soluble components which guide the Ca through pores in the hydrophobic layers into the interior of the matrix-coated space. It is only within this space that the mineral is deposited.     

Effects of larval diet on myrmecophilous qualities of Polyommatus icarus caterpillars (Lepidoptera: Lycaenidae)

Summary Fourth instar larvae of Polyommatus icarus maintain myrmecophilous associations with ants. In laboratory experiments, the attractiveness of larvae reared on foliage of the tree Robinia pseudacacia was significantly reduced compared with caterpillars fed with herbaceous Fabaceae. The ability to secrete carbohydraterich liquids from the dorsal nectary organ was also strongly reduced, while the function of the tentacle organs remained unaffected. The reductions in attractiveness and secretion abilities are caused by the food quality itself and not by secondary effects such as reduced larval size. The ecological significance of the results are discussed with respect to facultatively and obligately myrmecophilous lycacnids.