Functional aspects of Abscisic Acid Metabolism in Cotyledons of Phaseolus vulgaris L. Seedlings

During the early stages of germination and vegetative development,cotyledons of intact bean (Phaseolus vulgaris L.) seedlingsshowed active ABA catabolism causing a low endogenous ABA content.At the end of the substrate mobilizing phase, when the cotyledonsbecame senescent, a drastic increase of the endogenous ABA contentlinked with a decrease of the ABA catabolic activity was observed.This indicates that a close connection exists between senescenceand endogenous ABA content and metabolism in bean cotyledons. Removal of the apical growth region induced in the cotyledonsactivation of the ABA catabolism and the endogenous ABA concentrationdecreased below the detection limit (0.1 ng/g fr wt) at theonset of the outgrowth of the axillary buds. From then, apicaldominance was restored and the cotyledons returned to the senescentstate, which was correlated with a drastic increase of theirendogenous ABA content. ¹ Bevoegd verklaard navorser N. F. W. O. ² Wetenschappelijk medewerker F. K. F. O. (Received November 25, 1980; Accepted February 13, 1981)     

A thermodynamic study of Cu++−Zn++ ion exchange in theNitella flexilis cell wall

Summary Exchange isotherms of Cu²⁺ vs Zn²⁺-ions were performed on the cell wall of a fresh water alga,Nitella flexilis. The relevant thermodynamic parameters are calculated. The cell wall absorbs copper selectively. The selectivity is explained by a stronger chelation of the cupric ion, due to the Jahn-Teller effect. The wall acts like a two-site model, based on the nature of the ligands: a first group of aminesites reacts exothermically and a second of hydroxylic-carboxylic sites of lower affinity, reacts endothermically.     

Nematology—Status and Prospects: Let's Take Off Our Blinders and Broaden Our Horizons

Some aspects of current fundamental nematological research and teaching in agriculture, soil zoology, biology and medicine, and parasitology are explored as they relate to the Society of Nematologists and the science of nematology in its broadest sense.     

Studies on the bacteriophage MS2: XLI. Nature of the azure mutation

Azure (or reverse amber) mutants grow normally on wild-type Escherichia coli but not on host strains harbouring a strong UAG suppressor mutation. Three different bacteriophage MS2 azure mutants obtained by treatment with nitrous acid have been characterized at the nucleotide sequence level. The 3′-end fragment of the ³²P-labelled mutant genomes was isolated by DNA:RNA hybridization and treatment with nuclease S₁, and was analyzed by mini-fingerprinting of the RNA. It is known that the wild-type MS2 polymerase gene ends with a UAG codon, followed seven triplets further by an in-phase UAA triplet. All three azure mutants contained an A → G transition in this UAA second stop codon of the polymerase gene, resulting in a second suppressible UAG (amber) codon. Analysis of revertants demonstrated that the azure mutation can be counteracted either by a true site reversion at the second stop or by the creation of a new stop signal for the polymerase gene, either UAA (ochre) or UGA (opal), before or at the first stop, or beyond the second stop. On the basis of these results, a mechanism for the azure mutation is proposed. Silent mutations (one in the coding region, three in the untranslated 3′-terminal sequence) have also been observed in these phage stocks.     

Thyrotropin nyctohemeral pattern in primary depression : Differences between unipolar and bipolar women

The nyctohemeral patterns of serum thyrotropin (TSH) levels were studied in thirteen female patients suffering from primary affective illness (5 bipolars and 8 unipolars); they were compared to the nyctohemeral profiles obtained in six normal female subjects. The periodogram analysis showed striking differences in TSH circadian rhythms between unipolar and bipolar patients. The nyctohemeral TSH patterns in bipolar patients were similar to those obtained in controls. Unipolar patients, compared to controls, had a significantly lower 24-hour TSH mean, a lower sleep-wake ratio of TSH and an absence of nocturnal rise of TSH. The alterations of the circadian rhythm of TSH secretion observed in the depressive phase of unipolar illness may be a relevant neuroendocrine indicator of hypothalamic-pituitary dysfunction in primary depressive illness.     

Zinc deficiency in wetland rice along a toposequence of hydromorphic soils in the Philippines

Summary Zinc deficiency in rice induced by prolonged water saturation of the soil is widespread in the Philippines. The poor drainage associated with the disorder is mostly due to upwelling of shallow artesian water in footslope areas and to ponding of water from continually flowing artesian wells common in such areas. One toposequence where no Zn deficiency occurred in the highest field and progressively severe Zn deficiency in successive lower fields, was studied in detail. With lower elevation soils showed an increase in organic matter and free carbonate, associated with increased upwelling and ponding of artesian water very high in dissolved Mg and Ca bicarbonate.     

Perinatal mortality and XY/XX mosaicism

Summary An XX/XY mosaicism was detected in two phenotypically male newborns with perinatal death. The importance of chromosome studies at the paediatric necropsy and the significance of the present findings are discussed.