Hebe Saraví Cisneros

Instituto Patagónico para el Estudio de los Ecosistemas Continentales (IPEEC-CONICET)

Phenols can play a significant role in plant tolerance of drought and herbivory. We assessed the concentration, richness and structural complexity of soluble phenols (hereafter phenols) in leaves of different species representing different plant morphotypes of arid ecosystems. We selected seven species representative of the three main plant morphot...

Sheep grazing induces the reduction of perennial grass cover and the increase of shrub cover with high concentration of chemical defences. We analysed the effects of secondary metabolites released from green and senesced leaves of the shrub Larrea divaricata on soil microbial activity and the establishment of perennial grasses in arid ecosystems of...

The search for early indicators of stress (biomarkers) with low cost of determination (both economic and logistic) is a prominent issue in environmental studies. Consequently, an experimental study was conducted with the aim of validating the leaf shape variations as an early biomarker in plants growing in contaminated soils. We manipulated the Pb...

We aimed to evaluate the effects of both plant litter quality, characteristic of sites with different histories of grazing disturbance, and soil water content on nitrification in soils from an arid ecosystem of Patagonia. To reach this goal, soil microcosms covered by plant litter of different quality and subjected to different soil water condition...

Background and aims Our objective was to assess the effects of long-term continuous grazing on soil enzyme activities in relation to shifts in plant litter attributes and soil resources in an arid ecosystem, considering both spatial and temporal variations. Methods We randomly extracted soil samples with the respective litter cover at 5 modal size...

Desert shrubs often accumulate different types of phenolic compounds but what determines the amount and diversity of these compounds is an issue scarcely explored. The aim of this study was to assess differences in the amount and diversity of phenolic compounds in leaves among coexisting shrub species differing in rooting depth and leaf turnover. W...

Tautomerism of some nitriles has been studied by mass spectrometry. The analysis of the corresponding mass spectra has allowed to assign some fragmentations to specific tautomers and to determine heats of tautomerization through temperature effects and electron energy studies. Experimental determinations are supported by theoretical calculations. T...

Mass spectrometry is used to evaluate the occurrence of the nitrile-ketenimine tautomerism. Mass spectra of two differently substituted nitriles, ethyl-4,4-dicyano-3-methyl-3-butenoate and diethyl-2-cyano-3-methyl-2-pentenodiate are examined looking for common mass spectral behaviors. Ion fragmentation assignments for specific tautomers allow to pr...

A theoretical study of the mechanisms associated with the synthesis of anticonvulsant symmetric N,N-substituted sulfamides is presented. Two possible synthetic routes are compared, which mainly differ in the use of pyridine as a nucleophilic agent in the reaction mechanism. Geometry optimization techniques and transition-state detection at the B3LY...