Recovery from water stress in laurel plants: influence of short term potassium fertilization

Plant xylem hydraulic conductance varies with changes in sap solute concentrations, particularly potassium, a phenomenon known as 'ionic effect'. In well-watered Laurus nobilis plants, short term potassium fertilization increased xylem sap potassium concentration, resulting in an increase in plant hydraulic conductance (Kplant), leaf-specific conductivity of the shoot (kshoot) and transpiration rate (Eplant). The ionic effect is enhanced in embolized stems, where it can compensate the cavitation-induced loss of hydraulic conductance. The aim of this work was to test if water-stressed potassium-starved laurel plants could recover earlier from stress when irrigated with a potassium solution instead of water. Two-year-old potted laurel seedlings, grown under potassium-starved conditions, were subjected to water stress by suspending irrigation until leaf conductance to water vapor (gL) dropped to less than 50% of its initial value and leaf water potential (YL) reached turgor loss point (YTLP). Plants were then irrigated either with water or 25 mM KCl and measurements were taken at 3, 6 or 24 hours after irrigation. No significant differences were found between the two groups of plants in terms of YL, gL, Eplant, Kplant or kshoot. Analysis of xylem sap potassium concentration showed there were no significant differences between treatments, and potassium levels were similar to those of potassium-starved well-watered plants. In conclusion, potassium uptake or release to xylem appeared to be impaired at least up to 24 hours after relief from water stress, so fertilization after the onset of stress did not result in any short term advantage for recovery from drought stress

Organic Electrochemical Transistors

Organic electrochemical transistors (OECTs) leverage ion injection from an electrolyte into an organic semiconductor film to yield compelling advances in biological interfacing, printed logic circuitry and neuromorphic devices. Their defining characteristic is the coupling between electronic and ionic charges within the volume of an organic film. In this review we discuss the mechanism of operation and the materials that are being used, overview the various form factors, fabrication technologies and proposed applications, and take a critical look at the future of OECT research and development

Intrinsic hole mobility and trapping in a regio-regular poly(thiophene)

The transport properties of high-performance thin-film transistors (TFT) made with a regio-regular poly(thiophene) semiconductor (PQT-12) are reported. The room-temperature field-effect mobility of the devices varied between 0.004 cm2/V s and 0.1 cm2/V s and was controlled through thermal processing of the material, which modified the structural order. The transport properties of TFTs were studied as a function of temperature. The field-effect mobility is thermally activated in all films at T<200 K and the activation energy depends on the charge density in the channel. The experimental data is compared to theoretical models for transport, and we argue that a model based on the existence of a mobility edge and an exponential distribution of traps provides the best interpretation of the data. The differences in room-temperature mobility are attributed to different widths of the shallow localized state distribution at the edge of the valence band due to structural disorder in the film. The free carrier mobility of the mobile states in the ordered regions of the film is the same in all structural modifications and is estimated to be between 1 and 4 cm2/V s.Comment: 20 pages, 8 figure

Tailoring the Surface Chemistry of PEDOT:PSS to Promote Supported Lipid Bilayer Formation

This communication reports on a versatile and substrate-agnostic method to tune the surface chemistry of conducting polymers with the aim of bridging the chemical mismatch between bioelectronic devices and biological systems. As a proof of concept, the surface of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is grafted with a short-chain oligoethylene glycol monolayer to favor the formation of cell-derived supported lipid bilayers (SLBs). This method is tuned to optimize the affinity between the supported lipid bilayer and the conducting polymer, leading to significant improvements in bilayer quality and therefore electronic readouts. To validate the impact of surface functionalization on the system's ability to transduce biological phenomena into quantifiable electronic signals, the activity of a virus commonly used as a surrogate for SARS-CoV-2 (mouse hepatitis virus) is monitored with and without surface treatment. The functionalized devices exhibit significant improvements in electronic output, stemming from the improved SLB quality, therefore strengthening the case for the use of such an approach in membrane-on-a-chip systems

Structural origin of gap states in semicrystalline polymers and the implications for charge transport

We quantify the degree of disorder in the {\pi}-{\pi} stacking direction of crystallites of a high performing semicrystalline semiconducting polymer with advanced X-ray lineshape analysis. Using first principles calculations, we obtain the density of states of a system of {\pi}-{\pi} stacked polymer chains with increasing amounts of paracrystalline disorder. We find that for an aligned film of PBTTT the paracrystalline disorder is 7.3%. This type of disorder induces a tail of trap states with a breadth of ~100 meV as determined through calculation. This finding agrees with previous device modeling and provides physical justification for the mobility edge model.Comment: Text and figures are unchanged in the new version of the file. The only modification is the addition of a funding source to the acknowledgment

Successive Cambia: A Developmental Oddity or an Adaptive Structure?

BackgroundSecondary growth by successive cambia is a rare phenomenon in woody plant species. Only few plant species, within different phylogenetic clades, have secondary growth by more than one vascular cambium. Often, these successive cambia are organised concentrically. In the mangrove genus Avicennia however, the successive cambia seem to have a more complex organisation. This study aimed (i) at understanding the development of successive cambia by giving a three-dimensional description of the hydraulic architecture of Avicennia and (ii) at unveiling the possible adaptive nature of growth by successive cambia through a study of the ecological distribution of plant species with concentric internal phloem.ResultsAvicennia had a complex network of non-cylindrical wood patches, the complexity of which increased with more stressful ecological conditions. As internal phloem has been suggested to play a role in water storage and embolism repair, the spatial organisation of Avicennia wood could provide advantages in the ecologically stressful conditions species of this mangrove genus are growing in. Furthermore, we could observe that 84.9% of the woody shrub and tree species with concentric internal phloem occurred in either dry or saline environments strengthening the hypothesis that successive cambia provide the necessary advantages for survival in harsh environmental conditions.ConclusionsSuccessive cambia are an ecologically important characteristic, which seems strongly related with water-limited environments

High-efficiency and air-stable P3HT-based polymer solar cells with a new non-fullerene acceptor

We thank BASF for partial financial support, as well as EPSRC Projects EP/G037515/1 and EP/M023532/1, EC FP7 Project SC2 (610115), EC FP7 Project ArtESun (604397), EC FP7 Project POLYMED (612538), Project Synthetic carbon allotropes project SFB 953 and the King Abdullah University of Science and Technology (KAUST)

Efficiency Enhancement of Gallium Arsenide Photovoltaics Using Solution-Processed Zinc Oxide Nanoparticle Light Scattering Layers

We demonstrate a high-throughput, solution-based process for subwavelength surface texturing of a III-V compound solar cell. A zinc oxide (ZnO) nanoparticle ink is spray-coated directly on top of a gallium arsenide (GaAs) solar cell. The nanostructured ZnO films have demonstrated antireflection and light scattering properties over the visible/near-infrared (NIR) spectrum. The results show a broadband spectral enhancement of the solar cell external quantum efficiency (EQE), a 16% enhancement of short circuit current, and a 10% increase in photovoltaic efficiency