Post‐tectonic limitations on Early Devonian (Emsian) reef development in the Gobi‐Altai region,Mongolia

Pellegrini, A.F.A., Soja, C.M. & Minjin, C. 2011: Post‐tectonic limitations on Early Devonian (Emsian) reef development in the Gobi‐Altai region, Mongolia. Lethaia, Vol. 45, pp. 46–61. This study investigates a Lower Devonian (Emsian) carbonate sequence from the Chuluun Formation where it is exposed in the Gobi‐Altai region of southern Mongolia. Quantification of abundance patterns across guild, morphotype and general taxonomic levels was based on stratigraphical and thin‐section analyses. Comparison with other Emsian carbonate platforms allowed the factors that influenced community development in the wake of a tectonic perturbation to be determined. Our evidence reveals that potential reef‐building biotas preserved in the Chuluun Formation experienced rapid colonization of a newly submerged carbonate platform following an episode of tectonic uplift and the development of a coastal alluvial fan. Although critical reef‐building organisms were present, colonial corals and stromatoporoids exhibited limited vertical growth and showed no significant lateral expansion of individuals or biotic assemblages. Nor did those taxa experience significant increases in abundance, density, or size. We conclude that incomplete succession and the lack of reef development occurred most likely because of an unsuitable substrate, limited accommodation space and isolation that reduced colonization potential. □Community succession, Emsian, palaeoecology, reef suppression.     

Early Devonia benthic communities of the Alexander Terrane, southeastern Alaska

Emsian (upper Lower Devonian) limestones exposed on Kasaan, Round, and Wadleigh Islands in southeastern Alaska are part of an allochthonous suitc of island are deposits preserved within the accrctionary Alexander Terrane. Ten benthic marine communities, including several new brachiopod associations, are defined on the basis of field data correlated with a cluster analysis. Biologic and sedimentologic evidence is integrated with community group assignments in order to substantiate the paleoecology and evolutionary history of each community. These faunas were adapted to a spectrum of quiet and rough water habitats, including restricted, shallow subtidal areas nearshore, offshore biostromal banks, and open and restricted portions of a lagoon or shelf. Comparisons with coeval assemblages from the Cordillera and elsewhere reveal that these communities are unique to southeastern Alaska. Their origin within an early Paleozoic island are appears to have led to biogeographic isolation from other parts of the Cordillera and the development of a distinct biota at a site offshorc from the ancient continental margin. ▭ Emsian, paleocommunities, community groups, cluster analysis, Alexander Terrane.     

Plastid terminal oxidase (PTOX) has the potential to act as a safety valve for excess excitation energy in the alpine plant species Ranunculus glacialis L.

Ranunculus glacialis leaves were tested for their plastid terminal oxidase (PTOX) content and electron flow to photorespiration and to alternative acceptors. In shade‐leaves, the PTOX and NAD(P)H dehydrogenase (NDH) content were markedly lower than in sun‐leaves. Carbon assimilation/light and C_i response curves were not different in sun‐ and shade‐leaves, but photosynthetic capacity was the highest in sun‐leaves. Based on calculation of the apparent specificity factor of ribulose 1·5‐bisphosphate carboxylase/oxygenase (Rubisco), the magnitude of alternative electron flow unrelated to carboxylation and oxygenation of Rubisco correlated to the PTOX content in sun‐, shade‐ and growth chamber‐leaves. Similarly, fluorescence induction kinetics indicated more complete and more rapid reoxidation of the plastoquinone (PQ) pool in sun‐ than in shade‐leaves. Blocking electron flow to assimilation, photorespiration and the Mehler reaction with appropriate inhibitors showed that sun‐leaves were able to maintain higher electron flow and PQ oxidation. The results suggest that PTOX can act as a safety valve in R. glacialis leaves under conditions where incident photon flux density (PFD) exceeds the growth PFD and under conditions where the plastoquinone pool is highly reduced. Such conditions can occur frequently in alpine climates due to rapid light and temperature changes.     

Biological control of crown gall in cherry rootstock propagation

English isolates of Agrobacterium tumefaciens from cherry were sensitive to the bacteriocin produced by A. radiobacter strain 84 in vitro , and simultaneous inoculation of the two organisms into tomato stems or cherry leaf scars completely inhibited the gall formation that occurred in the absence of strain 84. However, attempts to achieve biological control of crown gall of cherry in the field were successful only when the antagonist was applied as a preplanting treatment to cuttings. Disease on infected cherry layers was not reduced even after three sprays of the antagonist. A. radiobacter strain 84 was also ineffective as a preplanting dip, or both preplanting and post-harvest dips for symptomless, but latently infected, rootstocks harvested from an infected layer bed.     

Effect of Phenolic Compounds on ABA-induced Changes in K+ Concentration of Guard Cells and in Epidermal Diffusive Resistance

The study of the structure-activity relationship of phenoliccompounds in reversing the ABA-effect on stomata led us to investigatethe changes in K⁺ concentrations in guard cells and in the epidermaldiffusive resistance of leaves, after treatment with ABA andphenolics. The amount of potassium localized in guard cells usually correspondsto stomatal aperture in different treatments. Umbelliferone,however, permits stomatal opening without retention of potassiumin the guard cells, which is an exception. The effect of phenolicsin retaining K⁺ in epidermal peels is matched by recorded epidermaldiffusive resistance changes in the leaves.Although flavonoidsand some other phenolics behave differently showing recoveryin epidermal peels with K⁺ in guard cells, epidermal diffusiveresistance is not recovered. Key words: Epidermal diffusive resistance, K⁺, ABA, phenolics, stomata     

Cytogenetic analysis in couples with recurrent miscarriages: a retrospective study from Punjab,north India

Human reproduction is considered as the most inefficient event as ～15–20% of human pregnancies end in miscarriage and in the product of miscarriages, chromosomal anomalies are a common occurrence. The aim of the present retrospective study was to assess the frequency of chromosomal aberrations in couples with recurrent miscarriages in the region of Punjab and to compare with worldwide frequencies. In this study, a total of 440 cases were referred between the period 1995–2015. After lymphocyte culturing, giemsa–trypsin banding was done for each case to assess the chromosomal anomalies. The frequency of chromosomal aberrations among couples was found to be 3.41% in our study. Among these aberrations, balanced reciprocal translocations formed the largest group with 60% anomalies. We would conclude that clinicians should understand the importance of chromosomal analysis in these couples and refer them for karyotyping after two miscarriages to rule out the possible genetic cause of recurrent miscarriages.     

A NOTE ON THE USE OF DEHYDRATED MILK AGAR FOR BACTERIAL COUNTS ON RAW AND DRIED MILKS

SUMMARY: The bacterial colony count of raw milk and of milk powder using milk agar prepared from a proprietary brand of the dehydrated medium has been compared with that obtained using the fresh medium prepared in the laboratory.
No significant difference was found in 17 milks which were examined using the roll-tube technique and 8 replicates/medium but in a second series of 32 milks the plate count (3 replicates/medium) was significantly lower on the reconstituted than on the fresh medium.
Some milk powders gave a much lower plate count on the reconstituted medium, due to the inability of the latter to support adequate growth of Streptococcus thermophilus.