Deciphering acoustic emission signals in drought stressed branches: the missing link between source and sensor

When drought occurs in plants, acoustic emission (AE) signals can be detected, but the actual causes of these signals are still unknown. By analyzing the waveforms of the measured signals, it should, however, be possible to trace the characteristics of the AE source and get information about the underlying physiological processes. A problem encountered during this analysis is that the waveform changes significantly from source to sensor and lack of knowledge on wave propagation impedes research progress made in this field. We used finite element modeling and the well-known pencil lead break source to investigate wave propagation in a branch. A cylindrical rod of polyvinyl chloride was first used to identify the theoretical propagation modes. Two wave propagation modes could be distinguished and we used the finite element model to interpret their behavior in terms of source position for both the PVC rod and a wooden rod. Both wave propagation modes were also identified in drying-induced signals from woody branches, and we used the obtained insights to provide recommendations for further AE research in plant science

Multi-residue analysis of pharmaceuticals in Belgian surface water : a novel screening-to-quantification approach using large-volume injection liquid chromatography coupled to high-resolution mass spectrometry

The ever growing number of emerging micropollutants such as pharmaceuticals requests rapid and sensitive full-spectrum analytical techniques. Time-of-flight highresolution mass spectrometry (TOF-HRMS) is a promising alternative for the state-ofthe- art MS/MS instruments because of its ability to simultaneously screen towards a virtually unlimited list of suspect compounds and to perform target quantification. The challenge for such suspect screening is to develop a strategy which minimizes the false negative rate without restraining numerous false positives. At the same time, omitting laborious sample enrichment through large-volume injection ultraperformance liquid chromatography (LVI-UPLC) is advantageous avoiding selective preconcentration. A novel suspect screening strategy was developed using LVI-UPLC-TOF-MS aiming the detection of 69 multi-class pharmaceuticals in surface water without the a priori availability of analytical standards. As a novel approach, the screening takes into account the signal intensity-dependent accurate mass error, hereby assuring the detection of 95% of pharmaceuticals present in surface water. Subsequently, the validation and applicability of the full-spectrum method for target quantification of the 69 pharmaceuticals in surface water is discussed. Analysis of five Belgian river water samples revealed the occurrence of 17 pharmaceuticals in a concentration range of 17 ng L-1 up to 3.1 μg L-1

New type of vulnerability curve gives insight in the hydraulic capacitance and conductivity of the xylem

Drought vulnerability of trees and other woody plants is much debated in the context of climate change, which creates a high interest in understanding plant water relations. The role and functioning of internal water storage is crucial, but still insufficiently understood. Drought vulnerability is typically assessed by considering loss in conductivity in function of decreasing xylem water potential, in a so-called ‘vulnerability curve’. The xylem water potential at which a certain percentage of conductivity is lost (usually 50%) gives an indication of the vulnerability to cavitation. In a ‘desorption curve’, we can examine the release of water from internal storage tissues with decreasing water potential. Both curves are very valuable, but rely on a sequence of manual measurements (xylem water potential, hydraulic conductivity and water content) and are time-consuming. Therefore, we propose a new type of vulnerability curve that is based on continuous measurements of diameter shrinkage and ultrasonic acoustic emissions (UAE). We monitored weight loss, xylem diameter shrinkage and UAE and measured xylem water potential during the dehydration of excised branches of Vitis vinifera L. ‘Johanniter’. The vulnerability curves could be interpreted in terms of water loss in elastic and inelastic tissues. The proposed method can be a tool to assess hydraulic capacitance and conductivity of the xylem

Leer luisteren naar de ultrasone taal van bomen

C