Differential tolerance of native and invasive tree seedlings from arid African deserts to drought and shade

Efforts to understand why some species become successful invaders and why some habitats are more at risk from invasive species is an important research focus in invasion ecology. With current global climate change, evaluation of the effects of shade and drought on cohabiting native and invasive species from extreme ecosystems is especially important. Acacia tortilis subsp. raddiana is a tree taxon native to arid African deserts. Prosopis glandulosa, native to the southwestern United States and Mexico, is invading African arid and semiarid regions that are habitat for A. t. subsp. raddiana. The aim of this study was to evaluate and compare the tolerance and responses of the seedlings of these two tree species to shade, water stress and their interactions. We measured and recorded growth rates and morphological, biochemical and physiological plant traits under two radiation and two water treatments in greenhouse conditions. Radiation intensity was a stronger driver of the performance of both species than water availability. Beyond the independent effects of shade and drought, the interactions of these factors yielded synergistic effects on seedlings of both tree species, affecting key plant traits. The seedlings of A. t. subsp. raddiana were able to implement important shifts in key functional traits in response to altering abiotic stress conditions, behaving as a stress-tolerant species that is well-adapted to the habitat it occupies in hot arid African deserts. In contrast, the fast-growing seedlings of P. glandulosa were stress-avoiding. The alien P. glandulosa seedlings were highly sensitive to water and shade stress. Moreover, they were particularly sensitive to drought in shade conditions. However, although alien P. glandulosa seedlings were exposed to high stress levels, they were able to avoid permanent damage to their photosynthetic apparatus by mechanisms such as increasing energy dissipation by heat emission and by adjusting the relative allocation of resources to above- and below-ground structures. Our results are useful for conservation planning and restoration of invaded hyperarid ecosystems

Photo-Fenton oxidation of cylindrospermopsin at neutral pH with LEDs

Cylindrospermopsin (CYN) is a potent cyanobacterial toxin found in freshwaters worldwide. In this work, the feasibility of the photo-Fenton process under neutral pH using light emitting diodes as irradiation source for the removal of this hazardous cyanotoxin from freshwater was investigated. The impact of the kind of iron chelating agent (ethylenediamine-N, N′-disuccinic acid vs. ethylenedinitrilotetraacetic acid) as well as the effect of the main operating conditions viz. H2O2 dose, Fe(III) load, initial CYN concentration, and Fe(III):EDDS molar ratio on the performance of the process was systematically evaluated. EDDS was selected as the most appropriate iron chelating agent considering the kinetics of the process and the environmental impact (Vibrio fischeri and Artemia salina). Under optimized conditions ([H2O2] = 30 mg L−1; [Fe(III)] = 5 mg L−1; Fe(III):ligand = 1:0.5 (molar ratio)), complete removal of CYN was achieved in 15-min reaction time. Furthermore, the catalytic system showed to be effective in real water matrices (river and reservoir waters) spiked with CYN. Although the presence of inorganic ions (mainly HCO3−/CO32−) and dissolved organic carbon decreased the oxidation rate of CYN due to scavenging reactions and iron coordination, respectively, complete elimination of the cyanotoxin was achieved in all cases. The fate of EDDS along the process was also evaluated to demonstrate that the catalytic system investigated, apart from its effectiveness, warrants the complete absence of residues after reaction. Therefore, the proposed system constitutes a promising method for cyanotoxin treatment either as a drinking water treatment step in conventional plants or as a potential remediation strategy in the natural environmentOpen Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This research has been supported by the CYTED Ibero-American Science and Technology Program for Development (CYTED-2019) through the project TALGENTOX (PCI2020-112013) and by the Spanish Ministry for Science and Innovation (MICINN) through the project PID2019-105079RB-I00. D. Ortiz has received a FPU predoctoral grant (FPU19/04816) from the Spanish Ministry of Universities. M. Munoz has received a Ramón y Cajal postdoctoral contract (RYC-2016–20648) from the Spanish MINEC

Influence of the soil water content and distribution on both the hydraulic and transpiration performance of 'Manzanilla' olive trees

8 páginas, 4 figuras, 20 referencias.-- VI International Symposium on Irrigation of Horticultural Crops, celebrado del 2-6 de noviembre de 2006 en Viña del Mar, Chile.-- [email protected] work was made with mature 'Manzanilla' olive trees in an orchard of a semi-arid area in southern Spain. Three water treatments were considered: Rainfed, in which the trees had rainfall as the only source of water supply; FAO, in which the trees were under localized irrigation to replace the crop water demand, with some roots left in drying soil; Pond, in which the whole rootzones of the trees were maintained under non-limiting soil water conditions for the whole dry season. Our aim was to obtain information on the mechanisms behind the reduction of transpiration (Ep) in the FAO trees, as compared to the Pond trees. Our results show a near-isohydric behaviour of the FAO trees, i.e. those trees under localized irrigation in which some roots are left in drying showed lower stomatal conductance than the Pond trees in which all roots were in wetted soil. This helped the FAO trees to maintain similar leaf water potentials than the Pond trees. In addition, the FAO trees maintained a constant difference between the water potential of the canopy and that in the soil. This has been described as an isohydrodynamic behaviour, and it is thought to be an improvement over a typically anisohydric behaviour. These mechanisms were behind the similar values of tree hydraulic conductance (K p) found in the FAO and Pond treatments. The Rainfed trees showed lower Kp values because of the low Ep values of those trees, due to the low soil water availability in that treatment. Our results show, however, that the Rainfed trees were able to maintain similar values of Kp all throughout the dry season, which shows that the hydraulic efficiency of the xylem of those trees was little affected by embolism, despite of the high demanding conditions in the area.This work has been funded by the Spanish Ministry of Education and Science, research project No.AGL2006-04666/AGR, and by the EU, research project ref. STREP 023120.Peer Reviewe

Influence of the aqueous matrix on the degradation of cyanotoxins by CWPO: a study on the Iberian Peninsula freshwaters

The increasing occurrence of toxic cyanobacterial blooms worldwide represents a critical health and environmental risk. Catalytic wet peroxide oxidation (CWPO) has emerged as an efficient and environmentally friendly technology for the removal of cyanotoxins in water. Nevertheless, its effectiveness has just been demonstrated in deionized water or simple synthetic aqueous matrices. In this work, the effect of the different components of the aqueous matrix on the CWPO of cyanotoxins was deeply evaluated considering the widespread properties of the Iberian Peninsula freshwaters. The presence of Cl-, HCO3- and SO42- ions reduced the oxidation rate of cylindrospermopsin (CYN) up to 70–80% at the highest concentrations tested (2000, 250 and 500 mg L−1 for Cl-, HCO3- and SO42-, respectively) due to their hydroxyl radical scavenging capacity. The presence of natural organic matter (NOM) resulted in a similar outcome (oxidation rate reduction up to 90% at the highest concentration tested, 20 mg L−1), but in this case due to the consumption of hydroxyl radicals in competition with CYN oxidation. The presence of NO3- and H2PO4- did not show any significant effect on CYN oxidation. Similarly, the presence of cyanobacteria (Chrysosporum ovalisporum, 50 µg chlorophyll-a L−1) did not appreciably affect the CYN oxidation rate. These results were consistent with those obtained by evaluating the impact of real aqueous matrices from drinking water treatment plants (DWTPs) located in Castilla y León and Extremadura regions (Spain) on CWPO performance. This knowledge is key to the implementation of the technology for the treatment of surface waters affected by toxic cyanobacterial bloomsThis research has been supported by the CYTED Ibero-American Science and Technology Program for Development (CYTED-2019) through the project TALGENTOX (PCI2020–112013) and by Spanish Ministry for Science and Innovation (MICINN) through the project PID2019–105079RB-I00. D. Ortiz thanks the Spanish Ministry of Universities (MIU) for the FPU predoctoral grant (FPU19/04816). M. Munoz thanks the Spanish MINECO for the Ramon ´ y Cajal postdoctoral contract (RYC-2016–20648). We especially thank Aqualia for providing the water samples from DWTPs employed in this study, which was performed in the framework of Rewaise project (http://rewaise.eu

Combining a process-based model of stomatal conductance with leaf turgor pressure related probe measurements to study the regulation of plant water status and stomatal conductance under drought

5 páginas.-- 4 figuras.-- 9 referencias.-- Comunicación oral presentada en el XII Luso-Spanish Symposium on Plant Water Relations – Water to Feed the World. 30th of September – 3rd of October (Evora) PortugalThe recently developed plant sensor of relative changes in leaf turgor pressure (LPCP probe) was compared with the turgor pressure output simulated with a process-based stomatal model (BMF model). Our results confirm the good agreement between the simulated turgor pressures and those derived from LPCP readings. The combined use of the BMF model and LPCP probes raised new insights into the regulation of hydraulic conductivity and osmotic pressureThis work was funded by the Spanish Ministry of Science and Innovation (research projects AGL2009-11310/AGR) and co-funded by FEDER programme. The first author benefited from a FPDI research fellowship from the Junta de Andalucía. We are grateful to A. Montero and V. Hernandez-Santana for assistance in the fieldPeer Reviewe

Stomatal control by drying roots in olive trees under localized irrigation

International audienc

SILVOLIVE, a Germplasm Collection of Wild Subspecies With High Genetic Variability as a Source of Rootstocks and Resistance Genes for Olive Breeding

15 páginas.- 5 figuras.- 1 tabla.- referencias.- The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fpls.2020.00629/full#supplementary-materialWild subspecies of Olea europaea constitute a source of genetic variability with huge potential for olive breeding to face global changes in Mediterranean-climate regions. We intend to identify wild olive genotypes with optimal adaptability to different environmental conditions to serve as a source of rootstocks and resistance genes for olive breeding. The SILVOLIVE collection includes 146 wild genotypes representative of the six O. europaea subspecies and early-generations hybrids. These genotypes came either from olive germplasm collections or from direct prospection in Spain, continental Africa and the Macaronesian archipelago. The collection was genotyped with plastid and nuclear markers, confirming the origin of the genotypes and their high genetic variability. Morphological and architectural parameters were quantified in 103 genotypes allowing the identification of three major groups of correlative traits including vigor, branching habits and the belowground-to-aboveground ratio. The occurrence of strong phenotypic variability in these traits within the germplasm collection has been shown. Furthermore, wild olive relatives are of great significance to be used as rootstocks for olive cultivation. Thus, as a proof of concept, different wild genotypes used as rootstocks were shown to regulate vigor parameters of the grafted cultivar “Picual” scion, which could improve the productivity of high-density hedgerow orchards.This work was supported by the FEDER-CSIC grant RECUPERA-2020 (Ref. 20134R089), the Grupos Operativos Intra-autonómicos FEDER-MAPAMA grant (Ref. 201600200066 29), and the Spanish National Research Council Proyectos Intramurales CSIC-201640E069, CSIC-201740E041, and CSIC-201940E077.Peer reviewe

Chloride at macronutrient levels increases drought resistance by improving water balance and water-use efficiency

Póster presentado en el SEB’s Annual Meeting 2-5 July (2019) Seville, SpainChloride (Cl-) has been recently described as a beneficial macronutrient in well-irrigated plants, playing specific roles in promoting plant growth, photosynthetic performance and water-use efficiency (WUE). Therefore, a new research framework is opened in the search for adaptive mechanisms that regulate water homeostasis and, in particular, the plant ability to withstand water deficit. Drought is now recognized as the abiotic stress that most importantly affects global crop productivity. Understanding how plants use water for optimal biomass production has become a fundamental issue worldwide. In this work, we aim to elucidate whether Cl- nutrition at macronutrient levels stimulates drought resistance and which physiological mechanisms are involved. To that end, tobacco plants were treated for 30 days with three nutritional treatments added to the basal solution: CL (5 mM Cl-), N (5 mM nitrate), and SP (1.25 mM sulphate and 1.875 mM phosphate), containing all of them the same cationic balance. Then, plants were subjected to two irrigation regimes for 20 days: control (100% field capacity) and moderate drought (60% field capacity). Results showed that, in comparison to SP and N treatments, Cl- application (CL treatment) improved plant growth, leaf development, water balance parameters and WUE under drought conditions. Interestingly, N-treated plants exhibited the strongest growth reduction during drought, showing higher stress symptoms caused by an inefficient water use. Therefore, we propose that the abundant uptake and accumulation of Cl- responds to an adaptive function that improves water relations and drought resistance in higher plants.N