Salt injury to plants with special reference to cations versus anions and ion activities

Summary In contrast with the toxicities of sulfate and chloride salts added to substrates, the anions SO₄ and C1 were not injurious when accumulated without leaf burning by cotton and tomato plants from atmospheres enriched with SO₂ or HC1 gases. The foregoing results are discussed in terms of cationenzyme interactions which appear to represent at least a major cause of salt toxicity. Although anions are largely unreactive with enzymes it has long been observed that chloride salts in soil solutions are far more toxic than sulfate salts. Five of seven species have shown nearly equal growth repressions on substrates with 100 me/1 of C1 salts versus 200 me of SO₄ salts, each added as 50 per cent Na. The ion activities of the two solutions were equal and the sum of cations in the plant saps were similar. The osmotic differentials (average about 10 atm) between the expressed tissue fluids and these substrate solutions were remarkably uniform within species. It is projected that the downward transport of salts via the phloem provides for root concentrations which supply ions to the xylem and thereby control the uptake of substrate salts.     

Inhibition of Transformation of Bacillus subtilis by Heavy Metals

Mercuric ions, as well as organomercuric ions and cadmium ions, can inhibit deoxyribonucleic acid-mediated transformation in Bacillus subtilis 168 without decreasing the viability of the total population. Differences in the inhibition of transformation by mercuric ions are identifiable on a temporal and concentration dependence basis. Sensitivity to low concentrations (9.2 x 10(-8) M) appears early in the uptake of deoxyribonucleic acid before the transformed markers have become insensitive to deoxyribonuclease. Resistance to "low concentrations" of Hg(2+) is kinetically indistinguishable from the requirement for magnesium in the transformation process. This inactivation is not reversed by the mercury-binding compound glutathione. Sensitivity to mercuric ions at a higher concentration (5.52 x 10(-7) M) occurs after the donor deoxyribonucleic acid has become insensitive to deoxyribonuclease. These complex interactions between mercuric ions and the process of transformation are discussed.     

The macronuclear envelope of Tetrahymena pyriformis GL in different physiological states

Summary Macronuclear envelopes were isolated from the ciliated protozoan Tetrahymena pyriformis GL, negatively stained and examined in the electron microscope. The frequency of central granules in the macronuclear pores was evaluated in five different physiological states: (1) stationary phase of growth, (2) exponential phase of growth, (3) heat-synchronized cultures at the end of the heat-synchronization treatment, (4) heat-synchronized cultures at the beginning of the first division, (5) heat-synchronized cultures at the end of the first division.The percentage of pores containing a central granule was markedly enhanced in heatsynchronized cultures at the end of the first division, i.e. a state known for an increase in ribosome formation. Actinomycin D was found to cause a significant decrease in central granule frequency.The observed alterations in central granule frequency seem to confirm the hypotheses which consider the central granule as representing a ribonucleoprotein particle in transit from nucleus to cytoplasm through the nuclear pore.For careful technical assistance I am indebted to Miss Marianne Whiter as well as to Drs. H. Falk, W.W. Franke and P. Sitte for helpful discussions. This work was supported in part by the Deutsche Forschungsgemeinschaft.     

Die Fimbrien von Rhizobium lupini 1/50, sta-

Zusammenfassung Die Fimbrien (oder Pili) einer nicht sternbildenden Mutante (1–50, sta^-) von Rhizobium lupini wurden elektronenmikroskopisch untersucht. Die Fimbien sind peritrich an der Bakterienzelle inseriert, und zwar während der exponentiellen Wachstumsphase meist einzeln. In der stationären Phase nehmen die Fimbrien an Zahl und Länge kontinuierlich stark zu; sie sind dann häufig büschelweise inseriert. Zusammen mit den oft zopfbildenden Geißeln verflechten sie sich zu einem ausgedehnten Netzwerk. Die Aneinanderlagerung der Fimbrien erfolgt unspezifisch durch Kohäsion; durch ebenfalls unspezifische Adhäsion haften sie auf dem Substrat.Die Fimbrien haben ca. 30 Å Durchmesser und sind röhrenförmig gebaut. Ihre lichte Weite beträgt 8 bis 10 Å. Ein allgemeines Bauschema der Fimbrien wird diskutiert. In der Diskussion über die allgemeine Funktion aller Arten von Fimbrien wird ihre Haftfähigkeit herausgestellt. Die Fimbrien der Mutante 1/50, sta^- sind wegen ihres geringen Innendurchmessers nicht als Transportröhren für doppelsträngige DNS und wahrscheinlich auch nicht für einzelsträngige DNS oder RNS geeignet.

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The fimbriae of Rhizobium lupini 1/50, sta^-

Summary The fimbriae (pili) of a non-starforming mutant (1/50, sta^-) of Rhizobium lupini were studied under the electron microscope. In the exponential phase of growth, fimbriae are singly, peritrichously inserted. During stationary growth these fimbriae increase by number and length. Together with the larger flagella they often form an extended reticulum. The fimbriae often stick together by unspecific cohesion forces; their attachment to the substrate can be explained by unspecific adhesion.The outer diameter of the fimbriae is 30 Å, the inner diameter 8 to 10 Å.The tubelike structure of fimbriae (pili) is discussed in terms of a general model.The most obvious general function of all types of fimbriae is their connecting power.The inner dimension of the fimbriae of the 1/50, sta^-—mutant exclude a model where they function as transport tubes for double-stranded DNA and probably for single stranded DNA or RNA either.

     

Microbodies (peroxisomes) in the toad,Bufo marinus

Summary Microbodies (peroxisomes), a group of cytoplasmic organelles enriched in catalase, are demonstrated in the toad, Bufo marinus, by light and electron microscopy by means of a cytochemical staining procedure that demonstrates the peroxidatic activity of catalase with diaminobenzidine (DAB). Amphibian microbodies are similar to those of other classes in their fine structure and localization in hepatocytes and kidney, where they are prominent in the proximal tubular cells. Nucleoids are present only in renal microbodies. In the proximal renal tubule an unusual group of large brown granules are identified as lysosomes by their acid phosphatase, -glucosaminidase and -glucuronidase activities.This work was supported by U.S. Public Health Service Grants Nos. NS-06856 and HD 00674. We wish to thank Dr. Richard M. Hays who generously supplied us with toads; Dr. Alex B. Novikoff for making available facilities for ultramicrotomy, Miss Betty De Prest for technical assistance; Miss Marianne Van Hooren for preparation of the photomicrographs.