Controls of the hydraulic safety–efficiency trade-off

C.G. was supported by the Swiss National Science Foundation SNF (5231.00639.001.01). A.V. was supported by WSL visiting fellowship and IMAGINA project (Prometeo program 2019/110-Generalitat Valenciana). The CEAM Foundation is supported by Generalitat Valenciana

Testing transpiration rates of juvenile Aleppo pine trees using the heat ratio method under laboratory conditions

Tree transpiration considerably contributes to evaporative fluxes to the atmosphere in terrestrial ecosystems. Accurate transpiration quantification provides relevant information about forest water use and may benefit adaptive forest management, especially in a global change context. Tree transpiration can be measured by several methods, and sap flow measurements are one of the most valued. However, species-specific validations of these techniques are required to avoid undesirable bias. This is especially relevant in species with low transpiration rates where errors may be relevant, such as Aleppo pine trees (Pinus halepensis Mill.). Moreover, another significant source of uncertainty in sap flow measurements is probe misalignment. Hence, the aim of this study was to correlate transpiration rates estimated by sap flow probes using the heat ratio method (THRM) and load cells to independently monitor water transpiration in juvenile Aleppo pine trees. The corrections to improve transpiration measures, including misalignment correction, were applied to THRM results to test if the accuracy of results improved. These measurements were recorded in greenhouse under controlled conditions to implement different environmental conditions. The environmental variables that ruled the experiment, mainly vapour pressure deficit and soil water availability, spanned in a wide range of values. The results showed an accurate linear correspondence between TOBS and THRM for low and medium values, but moderate underestimations at high transpiration rates were observed. These underestimations were partly removed when applying probe misalignment correction. This study supports the notion that HRM offers accurate Aleppo pine transpiration estimations with low and medium values under a variety of abiotic conditions, which also has implications for HRM application in other isohydric species. The results also support the interest in the use of probe misalignment correction to estimate transpiration, mainly when high transpiration values are recorded. The results of this study can be considered as a preliminary approach for future research in order to improve the estimates of the transpiration rates of the Aleppo pine under the limiting conditions of the Mediterranean.This study was funded by the Spanish Ministry of Science, Innovation and Universities and the European Regional Development Fund through research projects “BLUEWATER-HYDROMED” (PID2019-111332RB-C21 MICINN/FEDER), “INERTIA_HYDROMED” (PID2019-111332RB-C22 MICINN/FEDER) and “VERSUS” (CGL2015-67466-R MICINN/FEDER), “IMAGINA– PROMETEOII/2019/110” funded by the Generalitat Valenciana. A.M. Sabater was supported by a European Social Fund and the Generalitat Valenciana with a PhD contract (ACIF/2018/279). The CEAM Foundation is supported by the Generalitat Valenciana (Spain)

Drone-based assessment of microsite-scale hydrological processes promoted by restoration actions in early post-mining ecological restoration stages

A successful choice of post-mining restoration activities in dry climates may depend on relevant features related to topographic characteristics, hydrological processes and vegetation development, which will determine functional recovery in these ecosystems. The combination of different restoration techniques to reestablish vegetation, such as sowing and plantation, implies the interspersion of bare-soil areas with vegetated areas in early plant development stages, which may result in an associated mosaic of hydrologic functioning. In this study, we conducted a drone-based assessment to disentangle the role played by microsite-scale hydrological processes (i.e., planting hole slope, sink volume capacity, individual catchment area, Flow Length Index) promoted by restoration actions in soil protection and vegetation development on the hillside scale. Based on two contrasting restoration scenarios (Steep hillside and Smooth hillside), the different applied restoration treatments conditioned the microtopographic processes on the planting hole scale and, therefore, resource redistribution. The main results showed higher planting hole functionality on the smooth hillsides than on steep hillside, which resulted in greater water availability and bigger vegetation patches. By addressing the role of hydrological processes on the microsite scale, our study contributes substantially to prior knowledge on the relevant factors for ecosystem development and post-mining restoration success. It also demonstrates that high-resolution drone images can be a very useful tool for monitoring restoration actions, especially in large, inaccessible and unstable restored areas.The study was funded by the LIFE TECMINE Project (LIFE16 ENV/ES/000159) from the European Programme for the Environment and Climate Action (2014–2020)*. L.M. was supported by the Spanish MICINN (PTA2019-018094). The CEAM foundation is funded by the Generalitat Valenciana

Innovative Techniques for Landscape Recovery after Clay Mining under Mediterranean Conditions

Open-pit mining results in profound modifications at different environmental scales that may persist for very long time periods, or even indefinitely. Considerable research efforts in mine reclamation strategies have been made, although reclamation failures are still common. In dry climates, such as in the Mediterranean Basin, successful actions may depend on features related to proper species selection and restoration techniques, which may substantially contribute to provide substrate stability and facilitate the regeneration of the main ecological processes. In this context, we developed the TECMINE case-study aimed to evaluate the feasibility and suitability of innovative restoration practices applied to clay-mine reclamation under Mediterranean conditions. The restoration strategy was designed at the landscape level with two main approaches: the recovery of natural geomorphology shapes and ecological restoration, including vegetation recovery and soil quality, based on proper reference ecosystems. After the geomorphological land remodeling, a combination of several innovative restoration techniques was implemented to reclaim plant communities and ecosystem functioning. These techniques involved: (i) accurate species selection according to microhabitat characteristics; (ii) high-quality plant production; (iii) surface remodeling to improve substrate stabilization; and (iv) implementing rainfall collection to enhance resources availability, soil fertility improvement and the amelioration of abiotic conditions for seedlings. Finally, we developed a monitoring program to assess the success of the implemented restoration techniques over time. The application of these innovative techniques has reported interesting results and represents a step forward in the improvement of mine restoration under Mediterranean climate.The study was funded by the LIFE TECMINE Project (LIFE16 ENV/ES/000159) from the European Programme for the Environment and Climate Action (2014–2020)*. L.M. was supported by the Spanish MICINN (PTA2019-018094). The CEAM foundation is funded by the Generalitat Valenciana

Nutrient status and transplant shock on Mediterranean shrubs under semiarid climate

Hemos utilizado diferentes regímenes de fertirrigación en vivero y fertilizante de liberación lenta para producir brinzales de cinco especies leñosas mediterráneas (Pistacia lentiscus, Quercus coccifera, Rhamnus lycioides, Rhamnus alaternus, Tetraclinis articulata) con características morfológicas y funcionales contrastadas, y hemos evaluado el efecto de estos tratamientos sobre la vitalidad (potencial de crecimiento de raíces) y comportamiento en el campo (supervivencia tras el shock de transplante). El tamaño de los brinzales varió sustancialmente con los tratamientos. Observamos una relación positiva entre el estado nutricional y el crecimiento potencial de raíces, relación que era consecuencia del tamaño de las plantas. Las deficiencias de nitrógeno y fósforo, la reducción de la dosis de nutrientes o el endurecimiento por reducción de la proporción de N en las últimas fases de cultivo en vivero favorecieron la supervivencia de los brinzales a corto plazo. No observamos relación positiva entre el crecimiento potencial de raíces y la resistencia al shock post-transplante. Estos resultados contrastan con los obtenidos en zonas con déficit hídrico menos acusado.We have analyzed the effect of different fertilizer types and doses on the morphology and performance of five semiarid shrubs commonly used in afforestation programmes. Species selected had contrasted morpho-functional traits: Pistacia lentiscus, Quercus coccifera, Rhamnus lycioides, Rhamnus alaternus, Tetraclinis articulata. We found a relationship between application regime and root growth potential (RGP). Most of the variation in RGP was explained by seedling size, suggesting that other effects of nutrient application were less important. Short-term mortality reduced by nitrogen and phosphorus deficiency and nutrient hardening. No positive relationship was observed between RGP and transplant shock. Results contrast with works carried out in sub-humid areas.Este trabajo ha sido financiado por CEAM-Fundación Bancaja y una beca de investigación concedida a R. Trubat en el marco del proyecto CREOAK

Alleviation of Zn toxicity by low water availability

Heavy metal contamination and drought are expected to increase in large areas worldwide. However, their combined effect on plant performance has been scantly analyzed. This study examines the effect of Zn supply at different water availabilities on morpho-physiological traits of Quercus suber L. in order to analyze the combined effects of both stresses. Seedlings were treated with four levels of zinc from 3 to 150 µM and exposed to low watering (LW) or high watering (HW) frequency in hydroponic culture, using a growth chamber. Under both watering regimes, Zn concentration in leaves and roots increased with Zn increment in nutrient solution. Nevertheless, at the highest Zn doses, Zn tissue concentrations were almost twice in HW than in LW seedlings. Functional traits as leaf photosynthetic rate and root hydraulic conductivity, and morphological traits as root length and root biomass decreased significantly in response to Zn supply. Auxin levels increased with Zn concentrations, suggesting the involvement of this phytohormone in the seedling response to this element. LW seedlings exposed to 150 µM Zn showed higher root length and root biomass than HW seedlings exposed to the same Zn dose. Our results suggest that low water availability could mitigate Zn toxicity by limiting internal accumulation. Morphological traits involved in the response to both stresses probably contributed to this response.This research was funded by the Spanish Ministry of Science and Innovation (Project GRACCIE, Programa Consolider-Ingenio 2010 (CSD 2007-00067) and SURVIVE (CGL-2011-30531-CO2-02)) and Generalitat Valenciana (FEEDBACKS-PROMETEO/2009/006). E. I. Hernández thanks the University of Alicante for her FPU research fellowship. CEAM is supported by Generalitat Valenciana

Forest Decline Triggered by Phloem Parasitism-Related Biotic Factors in Aleppo Pine (Pinus halepensis)

Climate models predict increasing mean temperatures and reduced precipitation for Mediterranean ecosystems already subjected to major hydrological fluctuations. Forest decline phenomena relate extreme droughts or heat waves with other organisms, e.g., insects or microorganisms acting as pests, but their role needs to be elucidated. A biotic factor responsible for forest diseases is Candidatus Phytoplasma pini which is a phloem-parasitism that negatively affects Spanish pine forests in drought-prone areas. In several healthy and declining Aleppo pine stands, we monitored pine infection by PCR (Polimerase Chain Reation), determined the tree phloem tissue terpene composition, carbohydrate content, measured several relevant morpho-physiological variables and examined trees affected by bark beetles. PCR confirmed C. P. pini infection was widespread in all stands, regardless of to the presence of symptomatically affected trees. However, visible symptomatic decline only occurred in trees living under more stressful conditions. The terpene composition of pines in declining stands differed from those in healthy ones, and could be related with bark beetle attacks when pines were previously weakened by the phytoplasma disease. Our results indicate that biotic factors, such as C. P. pini, affecting phloem tissue may be triggering factors for drought-mediated forest decline and suggest that phloem diseases can play a key role in forest declining processes during extreme drought.This research was funded by Sección de Defensa Fitosanitaria (Conservación del Medio Natural, Consejeria de Medio Ambiente, Comunidad de Madrid) and the Survive-2 project (CGL2015-69773-C2-2-P MINECO/FEDER) from the Spanish Government. The CEAM Foundation is supported by Generalitat Valenciana

Living in Drylands: Functional Adaptations of Trees and Shrubs to Cope with High Temperatures and Water Scarcity

Plant functioning and survival in drylands are affected by the combination of high solar radiation, high temperatures, low relative humidity, and the scarcity of available water. Many ecophysiological studies have dealt with the adaptation of plants to cope with these stresses in hot deserts, which are the territories that have better evoked the idea of a dryland. Nevertheless, drylands can also be found in some other areas of the Earth that are under the Mediterranean-type climates, which imposes a strong aridity during summer. In this review, plant species from hot deserts and Mediterranean-type climates serve as examples for describing and analyzing the different responses of trees and shrubs to aridity in drylands, with special emphasis on the structural and functional adaptations of plants to avoid the negative effects of high temperatures under drought conditions. First, we analyze the adaptations of plants to reduce the input of energy by diminishing the absorbed solar radiation through (i) modifications of leaf angle and (ii) changes in leaf optical properties. Afterwards, we analyze several strategies that enhance the ability for heat dissipation through (i) leaf size reduction and changes in leaf shape (e.g., through lobed leaves), and (ii) increased transpiration rates (i.e., water-spender strategy), with negative consequences in terms of photosynthetic capacity and water consumption, respectively. Finally, we also discuss the alternative strategy showed by water-saver plants, a common drought resistance strategy in hot and dry environments that reduces water consumption at the expense of diminishing the ability for leaf cooling. In conclusion, trees and shrubs living in drylands have developed effective functional adaptations to cope with the combination of high temperature and water scarcity, all of them with clear benefits for plant functioning and survival, but also with different costs concerning water use, carbon gain, and/or leaf cooling.This research was funded by Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA) grant number RTA2015-00054-C02-01, by Ministerio de Ciencia e Innovación grant number PID2019-106701RR-I00/AEI/10.13039/501100011033 and INERTIA project (PID-2019-111332-C22), project IMAGINA (Prometeu program/2019/110, GVA) and from Gobierno de Aragón H09_20R research group. Work of D.A.F. is supported by a FPI-INIA contract BES-2017-081208. CEAM is funded by Generalitat Valenciana

Identification of distinctive physiological and molecular responses to salt stress among tolerant and sensitive cultivars of broccoli (Brassica oleracea var. Italica)

[EN] Background Salt stress is one of the main constraints determining crop productivity, and therefore one of the main limitations for food production. The aim of this study was to characterize the salt stress response at the physiological and molecular level of different Broccoli (Brassica oleracea L. var. Italica Plenck) cultivars that were previously characterized in field and greenhouse trials as salt sensitive or salt tolerant. This study aimed to identify functional and molecular traits capable of predicting the ability of uncharacterized lines to cope with salt stress. For this purpose, this study measured different physiological parameters, hormones and metabolites under control and salt stress conditions. Results This study found significant differences among cultivars for stomatal conductance, transpiration, methionine, proline, threonine, abscisic acid, jasmonic acid and indolacetic acid. Salt tolerant cultivars were shown to accumulate less sodium and potassium in leaves and have a lower sodium to potassium ratio under salt stress. Analysis of primary metabolites indicated that salt tolerant cultivars have higher concentrations of several intermediates of the Krebs cycle and the substrates of some anaplerotic reactions. Conclusions This study has found that the energetic status of the plant, the sodium extrusion and the proline content are the limiting factors for broccoli tolerance to salt stress. Our results establish physiological and molecular traits useful as distinctive markers to predict salt tolerance in Broccoli or to design novel biotechnological or breeding strategies for improving broccoli tolerance to salt stress.This work was funded by Grant RTC-2017-6468-2-AR (APROXIMACIONES MOLECULARES PARA INCREMENTAR LA TOLERANCIA A SALINIDAD Y SEQUiA DEL BROCOLI) funded by MCIN/AEI/10.13039/501100011033 and by "ERDF A way of making Europe" by the European Union. S.C. is a recipient of grant FPU19/01977 from the Spanish Ministerio de Universidades. L.M. was supported by the Spanish MICINN (PTA2019-018094). L.M and A.V. activities were founded by Prometeu program (IMAGINA project, PROMETEU/2019/110). CEAM foundation is funded by Generalitat Valenciana. None of the funding bodies has participated in the design of the study or the collection, analysis, interpretation of data, nor in writing the manuscript.Chevilly-Tena, S.; Dolz-Edo, L.; Morcillo, L.; Vilagrosa, A.; López-Nicolás, JM.; Yenush, L.; Mulet, JM. (2021). Identification of distinctive physiological and molecular responses to salt stress among tolerant and sensitive cultivars of broccoli (Brassica oleracea var. Italica). BMC Plant Biology. 21(1):1-16. https://doi.org/10.1186/s12870-021-03263-4S11621