Isohydry (i.e., strong regulation of leaf water potential, Ψl) is commonly associated with strict stomatal regulation of transpiration under drought, which in turn is believed to minimize hydraulic ...risk at the expense of reduced carbon assimilation. Hence, the iso/anisohydric classification has been widely used to assess drought resistance and mortality mechanisms across species, with isohydric species being hypothetically more prone to carbon starvation and anisohydric species more vulnerable to hydraulic failure. These hypotheses and their underlying assumptions, however, have rarely been tested under controlled, experimental conditions. Our objective is to assess the physiological mechanisms underlying drought resistance differences between two co-occurring Mediterranean forest species with contrasting drought responses: Phillyrea latifolia L. (anisohydric and more resistant to drought) and Quercus ilex L. (isohydric and less drought resistant). A total of 100 large saplings (50 per species) were subjected to repeated drought treatments for a period of 3 years, after which Q. ilex showed 18% mortality whereas no mortality was detected in P. latifolia. Relatively isohydric behavior was confirmed for Q. ilex, but higher vulnerability to cavitation in this species implied that estimated embolism levels were similar across species (12-52% in Q. ilex vs ~30% in P. latifolia). We also found similar seasonal patterns of stomatal conductance and assimilation between species. If anything, the anisohydric P. latifolia tended to show lower assimilation rates than Q. ilex under extreme drought. Similar growth rates and carbon reserves dynamics in both species also suggests that P. latifolia was as carbon-constrained as Q. ilex. Increasing carbon reserves under extreme drought stress in both species, concurrent with Q. ilex mortality, suggests that mortality in our study was not triggered by carbon starvation. Our results warn against making direct connections between Ψl regulation, stomatal behavior and the mechanisms of drought-induced mortality in plants.
The increase in energy and fertilizer consumption makes it necessary to develop sustainable alternatives for agriculture. Anaerobic digestion and digestates appeared to be suitable options. However, ...untreated digestates still have high water content and can increase greenhouse gas emissions during storage and land application. In this study, manure-derived digestate and solid fraction of digestate after separation were treated with a novel solar drying technology to reduce their water content, combined with acidification to reduce the gaseous emissions. The acidified digestate and acidified solid fraction of digestate recovered more nitrogen and ammonia nitrogen than their respective non-acidified products (1.5–1.3 times for TN; 14 times for TAN). Ammonia and methane emissions were reduced up to 94% and 72% respectively, compared to the non-acidified ones, while N2O increased more than 3 times. Dried digestate and dried acidified digestate can be labeled as NPK organic fertilizer regarding the European regulation, and the dried solid fraction and the improved dried acidified solid fraction can be labeled as N or P organic fertilizer. Moreover, plant tests showed that N concentrations in fresh lettuce leaves were within the EU limit with all products in all the cases. However, zinc concentration appeared to be a limitation in some of the products as their concentration exceeded the European legal limits.
•A solar drying greenhouse was used to produce organic fertilizers from digestate.•Acidification reduced up to 94% and 72% emissions for NH3 and CH4 respectively.•The resulting products were compared with the current fertilizer EU legislation.•Phytotoxicity of the resulting organic fertilizers was tested with lettuce pot trials.
Specific root length (SRL, m g
−1
) is probably the most frequently measured morphological parameter of fine roots. It is believed to characterize economic aspects of the root system and to be ...indicative of environmental changes. The main objectives of this paper were to review and summarize the published SRL data for different tree species throughout Europe and to assess SRL under varying environmental conditions. Meta-analysis was used to summarize the response of SRL to the following manipulated environmental conditions: fertilization, irrigation, elevated temperature, elevated CO
2
, Al-stress, reduced light, heavy metal stress and physical disturbance of soil. SRL was found to be strongly dependent on the fine root classes, i.e. on the ectomycorrhizal short roots (ECM), and on the roots <0.5 mm, <1 mm, <2 mm and 1 - 2 mm in diameter SRL was largest for ECM and decreased with increasing diameter. Changes in soil factors influenced most strongly the SRL of ECM and roots <0.5 mm. The variation in the SRL components, root diameter and root tissue density, and their impact on the SRL value were computed. Meta-analyses showed that SRL decreased significantly under fertilization and Al-stress; it responded negatively to reduced light, elevated temperature and CO
2.
We suggest that SRL can be used successfully as an indicator of nutrient availability to trees in experimental conditions.
The use of trunk diameter fluctuations and their derived parameters for irrigation scheduling in woody crops is reviewed. The strengths and weaknesses of these continuously measured plant-based water ...stress indicators compared with other discretely measured indicators for diagnosing plant water status in young and mature trees are discussed. Aspects such as sensor reading variability, signal intensity and the relationship between trunk diameter fluctuations and plant water status are analyzed in order to assess their usefulness as water stress indicators. The physiological significance of maximum and minimum daily trunk diameter and maximum daily trunk shrinkage (MDS) are also considered. Current knowledge of irrigation protocols and baselines for obtaining maximum daily trunk shrinkage reference values is discussed and new research objectives are proposed. We analyze the response of woody crops to continuous deficit irrigation scheduled by maintaining MDS signal intensity at threshold values to generate mild, moderate and severe water stress and assess the possibility of using linear variable displacement transducer (LVDT) sensors in trunk as a precision tool for regulated deficit irrigation scheduling. Finally, the possibility of using MDS signal intensity as a tool to match the irrigation regime to tree water requirements is also reviewed.
Human Precision-cut intestinal slices (hPCIS) are used to study intestinal physiology, pathophysiology, drug efficacy, toxicology, kinetics, and metabolism. However, the use of this ex vivo model is ...restricted to approximately a 24 h timeframe because of declining viability of the hPCIS during traditional culture. We hypothesized that we could extend the hPCIS viability by using organoid medium. Therefore, we cultured hPCIS for up to 72 h in organoid media expansion medium (Emed) and differentiation medium (Dmed). After incubation, we assessed culture-induced changes on viability markers, specific cell type markers and we assessed the metabolic activity of enterocytes by measuring midazolam metabolite formation. We show that the adenosine triphosphate (ATP)/protein ratio of Emed-cultured hPCIS and morphology of both Emed- and Dmed-cultured hPCIS was improved compared to WME-cultured hPCIS. Emed-cultured hPCIS showed an increased expression of proliferation and stem cell markers, whereas Dmed-cultured hPCIS showed an increased expression of proliferation and enterocyte markers, along with increased midazolam metabolism. Using the Emed, the viability of hPCIS could be extended for up to 72 h, and proliferating stem cells remained preserved. Using Dmed, hPCS also remained viable for up to 72 h, and specifically rescued the metabolizing enterocytes during culture. In conclusion, by using two different organoid culture media, we could extend the hPCIS viability for up to 72 h of incubation and specifically steer stem cells or enterocytes towards their original function, metabolism, and proliferation, potentially allowing pharmacokinetic and toxicology studies beyond the 24 h timeframe.
•Irrigation effect on sap flux density profiles of cherry trees was tested.•Different methods to estimate sapwood depth were compared.•Linear decrease of sap flux density with depth was found for ...most of the trees.•Azimuthal profile of sap flux density was random and its variation was not affected by irrigation.
Information on tree water use in plantations for high quality wood is scarce, thus studies are needed to properly estimate the irrigation demand of these plantations. Plant water use estimation with sap flow sensors has been used extensively. However, biases in tree sap flow estimate can arise from variations on radial and azimuthal profiles of sap flux density and also from the sapwood area considered for the up-scaling from sap flux density to sap flux. This work aimed to (1) study the spatial variations of sap flux density in cherry trees in a timber orientated plantation, (2) compare several methods to estimate sapwood depth in cherry trees and (3) to evaluate the effect of drip irrigation on these factors. The results showed that most of the studied trees had decreasing radial sap flux density profiles with depth as expected. However, the three irrigated trees of bigger sizes still showed high sap flux densities in their inner tissues, at contrast with the rest of the trees and especially with the non irrigated ones of similar size with values close to 20% of the sap flux density measured at 1cm depth from cambium. On the other hand, the different methods tested to estimate sapwood depth gave significantly different results and only the two methods of visual identification in wood cores based on color change and measurements of sap flux densities along the xylem radius may be considered suitable for scaling purposes. Moreover, azimuthal variation pattern was found to be random in all the studied trees, and the ranking between the aspects (north, south, east and west) was not affected by either drip irrigation or sun exposition, and thus measuring sap flux density in any particular aspect has been shown to be suitable to estimate the overall tree sap flux. We conclude that more studies are necessary to properly assess the radial profile of sap flux density, especially when considering the high sap flux density in the inner tissues of the three bigger irrigated trees as compared to the other trees, and also how this pattern seemed to indicate sapwood depths values very contrasted to the ones estimated from color change in wood cores.
► We downscale model climate projections and water balance at subwatershed level. ► Pluridisciplinary approach includes FAO procedure to estimate real crop water needs. ► Water availability would ...decrease and irrigation needs increase for all crops. ► Changes in phenology and physiology would be partly responsible of the results. ► We consider different adaptive measures for crops in front of global change.
To evaluate the vulnerability of agriculture under Mediterranean conditions, the real water needs of agriculture in the Fluvià watershed (Catalonia, NE Spain) were estimated for the XXIst century using a combination of downscaled climate projections (ECHAM5 plus MM5) in two IPCC scenarios (B1 and A2), watershed hydrological model (SWAT) and FAO procedure to calculate crop potential evapotranspiration. In comparison with baseline conditions (1984–2008), climate projections predicted a 12% (B1) to 28% (A2) reduction in precipitation, and a 2.2°C (B1) to 3.6°C (A2) increment of mean annual temperature at the end of the XXI Century (2076–2100). The changes of the environmental conditions would affect the real water availability in different crops: water required for irrigation would increase significantly along the century, ranging from 40 to 250% depending on the crop, because of a direct decrease in the amount of water available along the growing season and because of the effects of the projected climatic conditions on potential evapotranspiration (ET0) and on the phenology of these crops. Results are showing the high sensitivity of agriculture, despite its expanding technology, to changes in climate, and even more to site, plot, orchard or terroir conditions.
•Different contribution of low and high flows in the headwaters and the lower reaches.•Capacity of the reservoir network to reduce catastrophic floods is debatable.•Reservoirs have affected the ...frequency and severity of hydrological droughts.
The Segre basin (northeastern Spain).
The Segre basin is extensively regulated, through a dense network of dams, during the second half of the 20th century. This study assessed the impact of river regulation on the evolution of hydroclimatological extreme events across the basin during the past six decades (1950–2013). We assessed whether the occurrence of floods and hydrological droughts has changed, and whether these changes have differed spatially between the headwaters and lower areas of the basin. For this purpose, we employed a set of hydroclimatological indices in order to quantify the evolution of the amount as well as the frequency of quantiles of high precipitation and flood events. Changes in these variables were assessed by means of the nonparametric Mann–Kendall Tau coefficient.
Results reveal a general reduction in the occurrence of extreme precipitation events in the Segre basin from 1950 to 2013, which corresponded to a general reduction in high flows measured at various gauged stations across the basin. While this study demonstrates spatial differences in the decrease of streamflow between the headwaters and the lower parts of the basin, mainly associated with changes in river regulation, there was no reduction in the frequency of the extraordinary floods. Changes in water management practices in the basin have significantly impacted the frequency, duration, and severity of hydrological droughts downstream of the main dams, as a consequence of the intense water regulation to meet water demands for irrigation and livestock farms. Nonetheless, the hydrological response of the headwaters to these droughts differed markedly from that of the lower areas of the basin.
•Sap flow from irrigated and non-irrigated wild cherry trees was monitored.•Canopy conductance responses to environmental factors were studied.•The Jarvis–Stewart approach isolated properly the role ...of environmental factors.•Air temperature and soil water content greatly affected canopy conductance.•Tree pruning reduced transpiration and consequently affected water productivity.
In recent decades, wild cherry has been one of the species most widely used for reforestation in Europe. Studies aiming to select and improve trees to give them the best growth rates and wood properties have increased in response to growers’ demands. However, information relating to key physiological processes such as transpiration or stomatal conductance and to the effect of the common practice of pruning on plant–water relations is scarce. The main objective of this study was to assess the effects of environmental conditions on canopy conductance dynamics. Its secondary objective was to examine the short- and medium-term effects of branch pruning on tree transpiration, growth and derived water productivity. To this end, we measured sap flow in an experimental plantation where trees were subjected to drip irrigation and rain-fed conditions and where variables characterizing climate, soil and tree growth were also monitored. The results demonstrated that the Jarvis–Stewart approach was appropriate for studying the responses of canopy conductance to environmental factors. As well as the role of vapour pressure deficit and net radiation in controlling the daily variations of canopy conductance, the single effects of decreasing soil water content (optimum relative extractable water, REW, higher than 0.4) and increasing air temperature (optimum of 21 °C), as summer conditions approached, were correctly incorporated into the modelling exercise. Soil water content exerted the greatest control on canopy conductance for trees growing under rain-fed conditions, while air temperature did for irrigated trees. Pruning significantly reduced transpiration to about 35% when pre- and post-sub-periods were compared, but also affected annual water productivity regardless of the irrigation treatment. To assess the long-term effects of pruning on water productivity, measurements in both pruned and unpruned trees would be desirable.
Sap flow and maximum daily shrinkage (MDS) are two parameters that can be used for irrigation decision-making. An assay was raised under controlled conditions where drought was imposed by irrigation ...withdrawal in cherry plants to compare their response of MDS with that of other ecophysiological parameters commonly used in water relations studies. Results showed contrasting relationships between MDS and sap flow depending on the degree of water stress that could be due to stomatal regulation. At a daily timescale, trunk diameter variation and sap flow were related to each other via a loop that differs according to tree water status. MDS resulted more sensitive to drought than sap flow, but the simultaneous use of both indicators rendered complementary information sensitive to the water status of the plants.
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