Jorge Bernardo Jiménez

trans-Resveratrol and Grape Disease Resistance. A Dynamical Study by High-Resolution Laser-Based Techniques

Two modern laser-based techniques were synchronously applied to study the dynamics of the trans-resveratrol activity in Botrytis cinerea-infected grapes. Direct analysis of trans-resveratrol in both infected and noninfected grapes (Vitis vinifera, Aledo variety) was performed by using an analytical technique incorporating laser desorption coupled with laser resonant ionization and time-of-flight mass spectrometry. On the other hand, one of the most sensitive on-line methods for trace gas detection, laser photoacoustic spectroscopy, was used to investigate the involvement of the plant hormone ethylene (C2H4) in theB. cinerea grapes interaction and its temporal relationship with the trans-resveratrol content upon infection. The trans-resveratrol content and the ethylene released by noninfected grapes showed an opposite behavior. In this case, a high trans-resveratrol content corresponds to a low ethylene emission. For the B. cinerea-infected grapes, ethylene emission rises up after 48 h when the analogous content of trans-resveratrol started to decrease irreversibly. Moreover, the activity of trans-resveratrol as natural pesticide has been investigated by exogenous application on grapes. A short submerge (5 s) of the grapes in 1.6 × 10−4 m solution of trans-resveratrol delays the increase of C2H4 emission with about 48 h and produces a decrease of the C2H4 concentration and its emission rate. The treatment has positive effects on fruit conservation during storage; it doubled the normal shelf-life of grapes at room temperature, maintaining their post-harvest quality within 10 d.

Spectroscopy and dynamics of van der Waals reactions: the Ba⋯FCH3∗ photofragmentation channels

Abstract The simultaneous measurement of both the photodepletion action spectrum of the Ba⋯FCH 3 complex and the action spectra of the reactive BaF and non-reactive Ba photofragmentation channels, over the energy range 17795–18250 cm −1 allowed direct determination of the reaction probabilities of a van der Waals reaction as a function of excitation energy. The energy dependence of the Ba⋯FCH 3 + hν →(Ba⋯FCH 3 ) ∗ →BaF ∗ +CH 3 and Ba ∗ +CH 3 reaction probabilities showed an oscillatory behaviour with opposite phase, which could be due to quantal interferences between the two photofragmentation channels. In addition the energy spacing of the oscillations can be related to the internal motions of the transition state.

Resonances in the Ba…FCH3+hν→BaF+CH3 reaction probability

By measuring both the Ba…FCH3 photodepletion and the BaF action spectra, the Ba…FCH3+hν→BaF+CH3 reaction probability, PR(E), has been determined over the 16 065–16 340 cm−1 energy range. PR(E) shows a peak structure with an energy spacing of 10.9 cm−1 that may be related to the internal motion of the transition state of the reaction.

Excitation laser fluence effects on the Ba⋯FCH3+hν→BaF+CH3 intracluster reaction

Abstract In this work, results on the Ba ⋯ FCH 3 +hν→ BaF ( Ba ∗ )+ CH 3 ( CH 3 F ) reaction obtained under high laser field conditions are reported. We have found that the two-photodissociation channel yields, i.e. the reactive BaF and non-reactive Ba ∗ products, exhibited opposite behaviour depending upon the laser fluence. Whereas the BaF yield rises as the laser fluence is increased, the Ba ∗ yield decreases over the same laser fluence range. In other words, the product ( Ba ∗ ) /(BaF) branching ratio changes significantly from low to high laser fluence in such a way that the (photoinitiated) Ba⋯FCH3→BaF+CH3 reaction may be controlled by changing the intensity of the excitation laser field.