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eaf water potential (psi(leaf)), typically measured using the pressure chamber, is the most important metric of plant water status, providing high theoretical value and information content for multiple applications in quantifying critical physiological processes including drought responses. Pressure chamber measurements of psi(leaf) (psi(leafPC)) are most typical, yet, the practical complexity of the technique and of the underlying theory has led to ambiguous understanding of the conditions to optimize measurements. Consequently, specific techniques and precautions diversified across the global research community, raising questions of reliability and repeatability. Here, we surveyed specific methods of psi(leafPC) from multiple laboratories, and synthesized experiments testing common assumptions and practices in psi(leafPC) for diverse species: (i) the need for equilibration of previously transpiring leaves; (ii) leaf storage before measurement; (iii) the equilibration of psi(leaf) for leaves on bagged branches of a range of dehydration; (iv) the equilibration of psi(leaf) across the lamina for bagged leaves, and the accuracy of measuring leaves with artificially 'elongated petioles'; (v) the need in psi(leaf) measurements for bagging leaves and high humidity within the chamber; (vi) the need to avoid liquid water on leaf surfaces; (vii) the use of 'pulse' pressurization versus gradual pressurization; and (viii) variation among experimenters in psi(leafPC) determination. Based on our findings we provide a best practice protocol to maximise accuracy, and provide recommendations for ongoing species-specific tests of important assumptions in future studies.

Peat lands are archives of past diversity, climate, and other environmental conditions. The redistribution of radionuclides in a peat bog after a fire consists of change in vertical distribution and releases/losses to the atmosphere through evaporation and resuspension. The study of different radionuclides such as plutonium isotopes will be important to understand the radiation exposures to man following fire on contaminated land. In this work, a fast and sequential procedure for uranium, plutonium and americium determination in soil samples is presented. Together with the study of redistribution of uranium and plutonium isotopes in a raised peat bog located in the nature reserve of Vakö Mire (south of Sweden) following a big fire (1992). The procedure is based on the four main steps of any radiochemical procedure: pre-treatment, isolation of radionuclides, source preparation and measurement via alpha spectrometry. The sequential separation of the radionuclides is performed by extraction chromatography, employing UTEVA resin in columns and DGA resin in cartridges. Once the procedure was established, two cores of the Vakö Mire peat bog were studied (one from the burnt area and another from the not affected area). The first 10cm of each core sliced in 1 cm layers were analyzed. The results for plutonium in the burnt core show an increase in the 239+240Pu activity concentration (Bq/m2) at the ash layer, while in the not affected area the concentration slightly increases with depth due to the global fallout. Regarding uranium isotopes, their behaviour in the peat bog is different from plutonium. The non-burnt area presents much higher values of activity concentration than the burnt one due to its higher inorganic content. The fire made this element easily movable via weathering conditions and as results the U content in the burnt core is hardly 10% of the total amount accumulated in the non-burnt area. Moreover, 234U and 238U isotopes were found in secular equilibrium.

Reduced stomatal conductance (gs) during soil drought in angiosperms may result from effects of leaf turgor on stomata and/or factors that do not directly depend on leaf turgor, including root-derived abscisic acid (ABA) signals. To quantify the roles of leaf turgor-mediated and leaf turgor-independent mechanisms in gs decline during drought, we measured drought responses of gs and water relations in three woody species (almond, grapevine and olive) under a range of conditions designed to generate independent variation in leaf and root turgor, including diurnal variation in evaporative demand and changes in plant hydraulic conductance and leaf osmotic pressure. We then applied these data to a process-based gs model and used a novel method to partition observed declines in gs during drought into contributions from each parameter in the model. Soil drought reduced gs by 63-84% across species, and the model reproduced these changes well (r2=0.91, P<0.0001, n=44) despite having only a single fitted parameter. Our analysis concluded that responses mediated by leaf turgor could explain over 87% of the observed decline in gs across species, adding to a growing body of evidence that challenges the root ABA-centric model of stomatal responses to drought.

There are limited studies available that have investigated the effects of different levels of water supply on the whole-plant gas exchange dynamics. The latter is related to the difficulty in measuring whole-canopy carbon fixation and water consumption, especially in field conditions. Whole-plant chambers can measure these fluxes, therefore the aims of this work were (i) to determine the relationship between whole-plant gas exchange compared to single leaf gas exchange; (ii) to validate whole-canopy chamber measurements using sap flow probes; (iii) to measure the effect of soil water availability on water use efficiency calculated from gas exchange measured using whole-plant chambers. For these purposes, an experiment was carried out during the 2014 season in an experimental vineyard using six-years-old plants of cv. Grenache. Two irrigation regimes were established, moderate irrigation (50 % ETo) and non-irrigation. Carbon fixation and transpiration were measured using whole-plant chambers at veraison and pre-harvest. Simultaneously, leaf gas exchange was measured at different canopy positions during the day in order to compare those measurements with the whole-plant chamber data. In parallel, sap flow measurements were continuously recorded using heat balance probes. Results showed that CO2 fixation measured at noon in sun exposed leaves oriented to the south presented the highest correlation coefficient with whole plant chamber data. Whole-plant transpiration measured with whole-plant chambers was slightly higher compared to the estimated from sap flow data in both irrigated and non-irrigated plants. In general intensive leaf-level measurements do not completely reflect the whole plant physiology, due to variability of leaf to leaf environmental conditions and plant regulation of gas exchange.

© 2015 Elsevier B.V. Knowledge about regulation of stomatal conductance is necessary to improve grapevine water use efficiency. The vast range of grapevine cultivars may allow choosing the best-performing ones to global changing conditions provided the understanding and characterization of their physiological responses. In this study, a comparison between two cultivars (Tempranillo and Grenache) with different reputation in water use efficiency was performed during two experimental years in field-conditions. Water relations, leaf gas exchange and abscisic acid (ABA) dynamics were measured at different phenological stages along the growing seasons. A clear difference in the regulation of leaf water relations was observed between cultivars under water stress conditions. Specifically, results showed that there is a clear relationship between hydraulic conductance (Kh) and stomatal regulation. However, ABA can exert a differentiating role on stomatal control during different stages within the grapevine growth period. Furthermore, this study showed that differences in osmotic adjustment could lead to substantial differentiation in the stomatal regulation and the leaf water use efficiency.

Predictions of climate change indicate an increase in water scarcity in Mediterranean areas. Therefore, improving water use efficiency (WUE) becomes crucial for sustainable viticulture in the Mediterranean for both grapevine growth and fruit productivity. Variability of WUE between cultivars presents an opportunity to select the most appropriate cultivars in viticultural areas with increasing aridity. In this review, an update on the variability of WUE in different grapevine cultivars and environmental conditions is presented. Most studies on WUE are focused at the leaf level and frequently used to estimate whole-plant WUE. However, there are large discrepancies when scaling-up WUE from leaf to whole-plant level. There are several structural and physiological processes, not included in leaf WUE measurements, considered as possible factors to solve the gap between leaf and whole-plant WUE. Canopy structure and plant respiration are described as the most important components involved in whole-plant WUE regulation, and proposed as potential targets for its improvement. © 2013 Elsevier B.V.

The climate change conditions predicted for the end of the current century are expected to have an impact on the performance of plants under natural conditions. The variables which are foreseen to have a larger effect are increased CO2 concentration and temperature. Although it is generally considered CO2 assimilation rate could be increased by the increasing levels of CO2, it has been reported in previous studies that acclimation to high CO2 results in reductions of physiological parameters involved in photosynthesis, like the maximum carboxylation rate (Vc,max), stomatal conductance (gs) and mesophyll conductance to CO2 (gm). On the one hand, most of the previous modeling efforts have neglected the potential role played by the acclimation of gm to high CO2 and temperature. On the other hand, the effect of climate change on plant clades other than angiosperms, like ferns, has received little attention, and there are no studies evaluating the potential impact of increasing CO2 and temperature on these species. In this study we predicted responses of several representative species among angiosperms, gymnosperms and ferns to increasing CO2 and temperature. Our results show that species with lower photosynthetic capacity – such as some ferns and gymnosperms – would be proportionally more favored under these foreseen environmental conditions. The main reason for this difference is the lower diffusion limitation imposed by gs and gm in plants having high capacity for photosynthesis among the angiosperms, which reduces the positive effect of increasing CO2. However, this apparent advantage of low-diffusion species would be canceled if the two conductances – gs and gm – acclimate and are down regulated to high CO2, which is basically unknown, especially for gymnosperms and ferns. Hence, for a better understanding of different plant responses to future climate, studies are urged in which the actual photosynthetic response/acclimation to increased CO2 and temperature of fern

Crown carbon gain is maximized for a given total water loss if stomatal conductance (gs) varies such that the marginal carbon product of water (∂A/∂E) remains invariant both over time and among leaves in a plant crown, provided the curvature of assimilation rate (A) versus transpiration rate (E) is negative. We tested this prediction across distinct crown positions in situ for the first time by parameterizing a biophysical model across 14 positions in four grapevine crowns (Vitis vinifera), computing optimal patterns of gs and E over a day and comparing these to the observed patterns. Observed water use was higher than optimal for leaves in the crown interior, but lower than optimal in most other positions. Crown carbon gain was 18% lower under measured gs than under optimal gs. Positive curvature occurred in 39.6% of cases due to low boundary layer conductance (gbw), and optimal gs was zero in 11% of cases because ∂A/∂E was below the target value at all gs. Some conclusions changed if we assumed infinite gbw, but optimal and measured E still diverged systematically in time and space. We conclude that the theory's spatial dimension and assumption of positive curvature require further experimental testing

Predictions of climate change indicate an increase in water scarcity in Mediterranean areas. Therefore, improving water use efficiency (WUE) becomes crucial for sustainable viticulture in the Mediterranean for both grapevine growth and fruit productivity. Variability of WUE between cultivars presents an opportunity to select the most appropriate cultivars in viticultural areas with increasing aridity. In this review, an update on the variability of WUE in different grapevine cultivars and environmental conditions is presented. Most studies on WUE are focused at the leaf level and frequently used to estimate whole-plant WUE. However, there are large discrepancies when scaling-up WUE from leaf to whole-plant level. There are several structural and physiological processes, not included in leaf WUE measurements, considered as possible factors to solve the gap between leaf and whole-plant WUE. Canopy structure and plant respiration are described as the most important components involved in whole-plant WUE regulation, and proposed as potential targets for its improvement.

In Mediterranean areas grapevine water use efficiency (WUE) is becoming an important issue as grapevine production and quality are largely dependent on irrigation, and given the large area of this crop in this region. Under semi-arid conditions, grapevine water consumption rises up to 700. mm/year (rainfall plus irrigation), thus great water amounts are needed for areas typically characterised by water scarcity during grapevine growing season. Therefore, improving WUE is a challenge to secure agriculture sustainability of viticulture in these areas. In the present work we evaluate the variation of leaf WUE over time (diurnal time) and space (at eight canopy positions) under irrigation, moderate and severe water stress in field-grown Tempranillo grapevines. Scaling up from the single leaf to the whole plant WUE values were tested comparing daily integrals of leaf water use efficiency (WUE Di) with midday leaf WUE ones showing a poor relationship, that become poured as water stress increased. To evaluate spatial variations of WUE inside the canopy daily integrals of WUE Di, were determined by leaf gas exchange measurements at eight canopy positions with marked differences in light exposition. Great variations in WUE Di at different canopy locations were mostly determined by the daily integral of light interception with a high regression coefficient for irrigated (0.98) and moderately water stressed plants (0.92), and lower for plants under severe water stress (0.68). This indicates that increased daily PAR interception by the leaf increases WUE Di. Moreover, those data suggest that improvements in whole-plant WUE up to 27% could be achieved by selective thinning of basal (locations 1 and 7) and internal (location 8) leaves of the canopy and that these theoretical benefits would be minor but still significant under water stress. © 2012 Elsevier B.V.

Strobilurins are one of the most important classes of agricultural fungicides. In addition to their anti-fungal effect, strobilurins have been reported to produce simultaneous effects in plant physiology. This study investigated whether the use of strobilurin fungicide improved water use efficiency in leaves of grapevines grown under field conditions in a Mediterranean climate in southern Spain. Fungicide was applied three times in the vineyard and measurements of leaf gas exchange, plant water status, abscisic acid concentration in sap ([ABA]), and carbon isotope composition in leaves were performed before and after applications. No clear effect on stomatal conductance, leaf water potential and intrinsic water use efficiency was found after three fungicide applications. ABA concentration was observed to increase after fungicide application on the first day, vanishing three days later. Despite this transient effect, evolution of [ABA] matched well with the evolution of leaf carbon isotope ratio, which can be used as a surrogate for plant water use efficiency. Morning stomatal conductance was negatively correlated to [ABA]. Yield was enhanced in strobilurin treated plants, whereas fruit quality remained unaltered.

Aims Three grapevine varieties original from different climates: Grenache, from Mediterranean origin; Syrah, from mesic origin and Chardonnay, from the humid zone of Burgundy (France) were used to study differential physiological responses to water deficit and sub-sequent recovery after re-watering. Moreover, the effect of the environmental growing conditions on water use efficiency (WUE) was also studied. Methods Changes of the lamina hydraulic conductance (K lamina ), transpiration, photosynthetic CO2 assimilation (A N ), stomatal conductance (g s ), mesophyll conductance to CO2 (g m ), chlorophyll fluorescence, and their interactions with other environmental conditions were followed during prolonged water stress and subsequent re-watering in Chardonnay, Grenache and Syrah. Results Grenache confirmed its reputation as isohydric and Chardonnay as anisohydric, but Syrah, a variety often considered as anisohydric, showed near-isohydric behaviour. Chardonnay displayed higher hydraulic conductance during both irrigation and water stress and a faster recovery after water stress as compared to the two isohydric-behaving varieties. Chardonnay attained lower decreases in stomatal conductance in response to water stress by delaying its adjustment of the lamina hydraulic conductance (K lamina ), which in turn resulted in the maintenance of higher photosynthesis and photosynthetic capacity, favoring faster recovery upon re-watering. The results do not support the common assumption that isohydric behaviour results in a better performance under water stress conditions. Indeed, under moderate water stress, Chardonnay showed some advantages over the two varieties displaying near-isohydric behaviour. Conclusions Integrated over a period including water stress imposition, acclimation and recovery Chardonnay displayed higher CO2 assimilation than Grenache and Syrah, which implies a higher yield potential under these conditions.

La incorporación creciente del ordenador en las aulas de Educación Infantil, así como la disponibilidad de un cada vez mayor número de programas destinados a este grupo de edad, nos hace plantear algunas cuestiones sobre los diferentes dispositivos de entrada utilizados por los niños. Para intentar aclarar algunas de estas dudas realizamos un estudio en dos aulas de 3 años de un colegio público, comparando la eficacia mostrada en el uso de tres periféricos de entrada: ratón, pantalla táctil y tableta gráfica con lápiz inalámbrico. Los resultados muestran como, en los grupos estudiados, el ratón sigue siendo posiblemente la opción más adecuada., The growing incorporation of the computer at the Early Childhood Education classrooms, as well as the readiness of an every time bigger number of programs dedicated to this age group, makes us outline some questions on the different input devices used by the children. To try to clarify some of these doubts we carry out a study in two 3 years-old classrooms of a public school, comparing the effectiveness shown in the use of three input peripherals: mouse, touch screen and PC tablet with cordless pen. The results show that, in the studied groups, the mouse continues being possibly the most appropriate option.