VA-mycorrhiza mediated P effect on growth and yield of sunflower (Helianthus annuus L.) at different P levels

A field trial was conducted to study the response of sunflower (Helianthus annuus L.) to different phosphorus levels (16, 24 or 32 kg P ha^–1) and inoculation with vesicular-arbuscular mycorrhizal fungus, Glomus fasciculatum on vertisol during summer 1993. At the vegetative stage of sunflower, percent mycorrhizal root colonization, spore count, dry biomass and P uptake did not differ significantly between inoculated and uninoculated control plants. However, at later stages (flowering and maturity) percent root colonization, spore count, total dry biomass and total P uptake were significantly higher in inoculated plants than in uninoculated control plants. The total dry biomass, P content and seed yield increased with increasing P level in uninoculated plants, whereas no significant difference was observed between 16 and 32 kg P ha^–1 in inoculated plants. The positive effect of mycorrhizal inoculation decreased with increasing P level above 16 kg P ha^–1, due to decreased percent root colonization and spore count at higher P levels.     

Plastochron index in relation to water stress in cowpea

Plastochron index (PI) in two genotypes of cowpea (Vigna unguiculata L. Walp) showed a remarkable sensitivity to water stress. A linear expression PI = 4.6179 + 0.7451 S (r² = 0.93) summarised the degree of sensitivity and predictability of PI to different stress levels (S). PI could be regarded as a stress sensitive trait in cowpea.     

Mode of Action of the Toxin from Pseudomonas phaseolicola: II. Mechanism of Inhibition of Bean Ornithine Carbamoyltransferase

A chlorosis-inducing toxin of Pseudomonas phaseolicola was examined for inhibition of ornithine carbamoyltransferease prepared from acetone powder of bean (Phaseolus vulgaris L.) plants. The enzyme has a pH optimum at 8.5, involves a ternary complex reaction mechanism, and shows Michaelis constants of 5.0 mm and 1.7 mm for ornithine and carbamoylphosphate, respectively. Assuming reversible catalysis, Michaelas constants of 11 mm and 3.3 mm are calculated for citrulline and arsenate. Toxin induces allosteric competitive inhibition in relation to carbamoylphosphate and a noncompetitive mode of inhibition in relation to ornithine, except at high toxin concentrations where uncompetitive inhibition is observed. In the backward assay, competitive inhibition is observed for both arsenate and citrulline. Inhibition is increased with preincubation time and shows saturation kinetics with regard to toxin concentration.     

The lymphocyte as a dosimeter: Comparison of somatic chromosome aberrations in 522 newborn infants and 602 mothers

Summary The frequency of somatic chromosomal aberrations was studied in 522 newborn infants and 602 mothers. Both the rates of aberrations on a per cell basis and the frequency of individuals with varying rates of aberrations were determined. All types of aberrations were more frequent in maternal cells, and the total chromosome break rate in mothers was three times higher than in neonates. Only 2 of the infants had structural rearrangements when 10 cells/newborn were analyzed, compared to 8, or more than 1%, of the mothers. In view of the relative rarity of chromosome aberrations in the neonatal cells, lymphocytes can be utilized as a convenient biological dosimeter for the surveillance of human populations from birth onwards.

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Zusammenfassung Die Häufigkeit somatischer Chromosomenaberrationen wurde bei 522 Neugeborenen und 602 Müttern untersucht. Es wurden sowohl die Aberrationen pro Zelle bestimmt als auch pro Individuum in jeweils 10 Zellen. Alle Aberrationstypen (Gaps, Brüche, Fragmente, Strukturumbau) waren häufiger in mütterlichen Zellen. Die Bruchrate war bei Müttern 3mal höher als bei Neugeborenen. Nur 2 der Kinder hatten strukturelle Umbauten, im Vergleich zu 8 der Mütter (mehr als 1%). Angesichts der relativen Seltenheit von Chromosomenaberrationen in Neugeborenenzellen können Lymphocyten als ein geeigneter biologischer Dosimeter für die Überwachung menschlicher Populationen von Geburt an verwendet werden.

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Research Supported by N. I. H. Contract No. PH 43-6-71463.     

Degradation of Endrin, Aldrin, and DDT by Soil Microorganisms

Twenty microbial cultures which had been shown to degrade dieldrin were tested to determine their ability to degrade endrin, aldrin, DDT, gamma isomers of benzenehexachloride (gamma-BHC), and Baygon. All isolates were able to degrade DDT and endrin, whereas 13 degraded aldrin. However, none of them was able to degrade Baygon or gamma-BHC.     

Influence of Antitranspirants on Rapeseed (Brassica campestris) Plants under Water-stressed and Nonstressed Conditions

Daily transpiration rate was decreased by low soil moisture, phenylmercuric acetate (PMA) in combination with kaolinite, Mobileaf (a filmforming wax emulsion manufactured by the Mobil Oil Co.), PMA alone, and kaolinite alone in this order. At high soil moisture, dry matter was decreased by PMA but was increased by Mobileaf and by PMA + kaolinite combination. At low soil moisture, dry matter was increased by Mobileaf.     

Histoenzymorphology of β-D-glucuronidase in cortical granules in oocytes of some representative vertebrates

Summary Histoenzymorphologic investigations on -D-glucuronidase in cortical granules in oocytes of some representative vertebrates revealed interesting differences in localisation of the enzyme in the two techniques employed using 8-hydroxyquinoline -D-glucosiduronic acid and naphthol AS-BI -D-glucosiduronic acid as substrates. In the former a nonspecific localisation in the entire cytoplasm of the oocytes excepting nucleus was evident whereas in the latter the cortical granules alone exhibited intense activity. To some extent this difference could be accounted for on the basis of yolk content of the eggs. -D-glucoronidase-rich lysosomal cortical granules were found in the amphibian, reptilian and avian oocytes whereas mammalian oocyte cortical granules were devoid of this enzyme. -D-glucuronidase in cortical granules was sensitive to low concentrations of Hg⁺⁺, Cu⁺⁺, glucuronic and mucic acids. Other histochemical evidence for the lysosomal nature of the cortical granules is presented and discussed. -D-glucuronidase seems to have a role in ovum-nutrition and activation which, thus, make a new addition to the existing knowledge of physiological role of -D-glucuronidase and lysosomes.Dr. A. T. Varute — Research Project guide.