Modified atmosphere packaging and dark/light refrigerated storage in green leafy vegetables have impact on nutritional value

The consumption of zeaxanthin (Z) through a vegetable-rich diet is recommended to reduce the progression of age-related macular degeneration. Due to Z’s intrinsic dynamic character that results from its participation in the photoprotective xanthophyll cycle involving the carotenoids violaxanthin, antheraxanthin and zeaxanthin (VAZ), post-harvest handling practices and storage usually retain low amounts of this bioactive compound (compared to the rest of phytochemicals that are, in general, more stable). Thus, the aim of this work was to investigate in important consumed leafy vegetables the effects of different storage conditions on carotenoids (mainly Z) including i) packaging under three modified atmospheres (MAs), ii) light refrigerated supermarket storage and iii) dark refrigerated domestic storage. The results showed that an MA with low O2 and high CO2 enhanced the Z content under light. Moreover, both light and dark refrigerated storage showed dynamic and circadian pigment changes that enhanced the total VAZ pool. These results can contribute to generating practical recommendations for industries, supermarkets, and consumers when high Z content is a nutritional target.RE received a Juan de la Cierva-incorporación grant IJCI-2014-21452. JB is a holder of a PhD fellowship from the Public University of Navarre. This research was supported by research BFU 2010-15021 and CTM2014- 53902-C2-2-P from the Ministry of Education and Science of Spain and the ERDF (FEDER) and research project UPV/EHU IT-1018-16. Technical and human support by Eroski supermarkets and “Fundación Tecnova” is gratefully acknowledged

On the recalcitrant use of Arnon’s method for chlorophyll determination

Letters - New Phytol.This work was supported by the Basque Government (UPV/EHU-GV IT-1018-16), and by the Spanish Ministry of Economy and Competitiveness (MINECO) and the ERDF (FEDER) (CTM2014-53902- C2-2-P). R.E. and B.F-M. received a ‘Juan de la Cierva-Incorporación" grant (IJCI-2014-21452 and IJCI-2014-22489, respectively)

Mechanisms of ammonium toxicity and the quest for tolerance

Ammonium sensitivity of plants is a worldwide problem, constraining crop production. Prolonged application of ammonium as the sole nitrogen source may result in physiological and morphological disorders that lead to decreased plant growth and toxicity. The main causes of ammonium toxicity/tolerance described until now include high ammonium assimilation by plants and/or low sensitivity to external pH acidification. The various ammonium transport-related components, especially the non-electrogenic influx of NH3 (related to the depletion of 15N) and the electrogenic influx of NH4+, may contribute to ammonium accumulation, and therefore to NH3 toxicity. However, this accumulation may be influenced by increasing K+ concentration in the root medium. Recently, new insights have been provided by “omics” studies, leading to a suggested involvement of GDP mannose-pyrophosphorylase in the response pathways of NH4+ stress. In this review, we highlight the cross-talk signaling between nitrate, auxins and NO, and the importance of the connection of the plants’ urea cycle to metabolism of polyamines. Overall, the tolerance and amelioration of ammonium toxicity are outlined to improve the yield of ammonium-grown plants. This review identifies future directions of research, focusing on the putative importance of aquaporins in ammonium influx, and on genes involved in ammonium sensitivity and tolerance.The authors acknowledge the support of research grants AGL2014-52396-P from the Spanish Ministry of Economy and Competitiveness (MINECO) and PTDC/BIA-BEC/099323/2008 and PTDC/BIA-ECS/122214/2010 from the Portuguese Fundação para a Ciência e Tecnologia (FCT). RE received a JAE-Doc-2011-046 fellow from the Spanish CSIC, co-financed by the European Social Fund

Traffic restrictions during COVID-19 lockdown improve air quality and reduce metal biodeposition in tree leaves

The coronavirus disease (COVID-19) has had a great global impact on human health, the life of people, and economies all over the world. However, in general, COVID-19´s effect on air quality has been positive due to the restrictions on social and economic activity. This study aimed to assess the impact on air quality and metal deposition of actions taken to reduce mobility in 2020 in two different urban locations. For this purpose, we analysed air pollution (NO2, NO, NOx, SO2, CO, PM10, O3) and metal accumulation in leaves of Tilia cordata collected from April to September 2020 in two cities in northern Spain (Pamplona-PA and San Sebastián-SS). We compared their values with data from the previous year (2019) (in which there were no mobility restrictions) obtained under an identical experimental design. We found that metal accumulation was mostly lower during 2020 (compared with 2019), and lockdown caused significant reductions in urban air pollution. Nitrogen oxides decreased by 33%−44%, CO by 24%−38%, and PM10 by 16%−24%. The contents of traffic-related metals were significantly reduced in both studied cities. More specifically, significant decreases in metals related to tyre and brake wear (Zn, Fe, and Cu) and road dust resuspension (Al, Ti, Fe, Mn, and Ca) were observed. With these results, we conclude that the main reason for the improvement in urban air pollutants and metals was the reduction in the use of cars due to COVID-19 lockdown. In addition, we offer some evidence indicating the suitability of T. cordata leaves as a tool for biomonitoring metal accumulation. This information is relevant for future use by the scientific community and policy makers to implement measures to reduce traffic air pollution in urban areas and to improve environmental and human health.This research was funded by the UPV/EHU-GV IT-1018-16 program (Basque Government)

Drought tolerance response of high-yielding soybean varieties to mild drought: physiological and photochemical adjustments

Soybean is a crop of agronomic importance that requires adequate watering during its growth to achieve high production. In this study, we determined physiological, photochemical and metabolic differences in five soybean varieties selected from the parental lines of a nested association mapping population during mild drought. These varieties have been described as high yielding (NE3001, HY1; LD01-5907, HY2) or drought tolerant (PI518751; HYD1; PI398881, HYD2). Nevertheless, there has been little research on the physiological traits that sustain their high productivity under water-limited conditions. The results indicate that high-yielding varieties under drought cope with the shortage of water by enhancing their photoprotective defences and invest in growth and productivity, linked to a higher intrinsic water use efficiency. This is the case of the variety N-3001 (HY1), with a tolerance strategy involving a faster transition into the reproductive stage to avoid the drought period. The present study highlights the role of the physiological and biochemical adjustments of various soybean varieties to cope with water-limited conditions. Moreover, the obtained results underscore the fact that the high phenotypic plasticity among soybean phenotypes should be exploited to compensate for the low genetic variability of this species when selecting plant productivity in constrained environments.This work was supported by grants from the Spanish Ministry of Science and Innovation and FEDER funds (AGL2014-52396) and from the Basque Government (UPV/EHU-GV IT-1018-16; IT-932-16). J.B. is a holder of a PhD fellowship from the Public University of Navarre. R.E. received a Juan de la Cierva-incorporacion grant (IJCI-2014-21452)

Photoprotective Strategies of Mediterranean Plants in Relation to Morphological Traits and Natural Environmental Pressure: A Meta-Analytical Approach

Despite being a small geographic extension, Mediterranean Basin is characterized by an exceptional plant biodiversity. Adaptive responses of this biocoenosis are delineated by an unusual temporal dissociation along the year between optimal temperature for growth and water availability. This fact generates the combination of two environmental stress factors: a period of summer drought, variable in length and intensity, and the occurrence of mild to cold winters. Both abiotic factors, trigger the generation of (photo) oxidative stress and plants orchestrate an arsenal of structural, physiological, biochemical, and molecular mechanisms to withstand such environmental injuries. In the last two decades an important effort has been made to characterize the adaptive morphological and ecophysiological traits behind plant survival strategies with an eye to predict how they will respond to future climatic changes. In the present work, we have compiled data from 89 studies following a meta-analytical approach with the aim of assessing the composition and plasticity of photosynthetic pigments and low-molecular-weight antioxidants (tocopherols, glutathione, and ascorbic acid) of wild Mediterranean plant species. The influence of internal plant and leaf factors on such composition together with the stress responsiveness, were also analyzed. This approach enabled to obtain data from 73 species of the Mediterranean flora, with the genus Quercus being the most frequently studied. Main highlights of present analysis are: (i) sort of photoprotective mechanisms do not differ between Mediterranean plants and other floras but they show higher plasticity indexes; (ii) a-tocopherol among the antioxidants and violaxanthin-cycle pigments show the highest responsiveness to environmental factors; (iii) both winter and drought stresses induce overnight retention of de-epoxidised violaxanthin-cycle pigments; (iv) this retention correlates with depressions of Fv/Fm; and (v) contrary to what could be expected, mature leaves showed higher accumulation of hydrophilic antioxidants than young leaves, and sclerophyllous leaves higher biochemical photoprotective demand than membranous leaves. In a global climatic change scenario,the plasticity of their photoprotective mechanisms will likely benefit Mediterranean species against oceanic ones. Nevertheless, deep research of ecoregions other than the Mediterranean Basin will be needed to fully understand photoprotection strategies of this extremely biodiverse floristic biome: the Mediterranean ecosystem.This work was supported by the Basque Government (UPV/EHU-GV IT-1018-16) and by the Spanish Ministry of Economy and Competitiveness (MINECO) and by the ERDF (FEDER) (CTM2014-53902-C2-2-P). RE and BF received a "Juan de la Cierva-Incorporacion" grant (IJCI-2014-21452 and IJCI-2014-22489, respectively). FM received a postdoctoral grant for Recent Ph.D. and MG is recipient of a specialization fellowship for Ph.D. researchers, both awarded by the Research Vice-Rectorate of the UPV/EHU

Holm oak decline is determined by shifts in fine root phenotypic plasticity in response to belowground stress

Climate change and pathogen outbreaks are the two major causes of decline in Mediterranean holm oak trees (Quercus ilex L. subsp. ballota (Desf.) Samp.). Crown-level changes in response to these stressful conditions have been widely documented but the responses of the root systems remain unexplored. The effects of environmental stress over roots and its potential role during the declining process need to be evaluated. We aimed to study how key morphological and architectural root parameters and nonstructural carbohydrates of roots are affected along a holm oak health gradient (i.e. within healthy, susceptible and declining trees). Holm oaks with different health statuses had different soil resource-uptake strategies. While healthy and susceptible trees showed a conservative resource-uptake strategy independently of soil nutrient availability, declining trees optimized soil resource acquisition by increasing the phenotypic plasticity of their fine root system. This increase in fine root phenotypic plasticity in declining holm oaks represents an energy-consuming strategy promoted to cope with the stress and at the expense of foliage maintenance. Our study describes a potential feedback loop resulting from strong unprecedented belowground stress that ultimately may lead to poor adaptation and tree death in the Spanish dehesa.This research was mainly funded by the Spanish Government through the IBERYCA project (CGL2017-84723-P), its associated FPI scholarship BES-2014-067971 (ME-V) and SMARTSOIL (PID2020-113244GB-C21). It was further supported by the BC3 María de Maeztu excellence accreditation (MDM-2017-0714; the Spanish Government) and by the BERC 2018–2021 and the UPV/EHU-GV IT-1018-16 programme (Basque Government). Additionally, this research was further supported through the ‘Juan de la Cierva programme’ (MV; IJCI-2017-34640; the Spanish Government) and one project funded by the Romanian Ministry of Research, Innovation and Digitization through UEFISCDI (A-MH; REASONING, PN-III-P1-1.1-TE-2019-1099)

Carotenoids and their derivatives: A “Swiss Army knife-like” multifunctional tool for fine-tuning plant-environment interactions

Plants have to cope with different biotic and abiotic stresses, such as the attacks of pathogens and herbivores, high irradiance, droughts, salt stress or nutrient deficiencies throughout their lifetime. These environmental perturbations lead to the regulation of the “primary” and “secondary” carotenoid network. The formers are produced and stored in plastids and they are necessary for photosynthesis and related functions. Otherwise, secondary carotenoids are derivatives of primary carotenoids. They perform other important functions not related to the photosynthetic process but essential for plant survival as regulators of growth and development or as signal molecules at all levels of plant organization. This review provides a complete revision of the status of all these carotenoids, highlighting their newly discovered functions involved in plant-environment interaction. Concurrently, this review covers recent information on how carotenoids perform critical functions for the survival of animals (including humans) and the way they are suitable diagnostic tools for assessing the functioning of terrestrial ecosystems.This work was supported in part by the grant UPV/EHU-GV IT-1648–22 (from the Basque Government, Spain), Phy2SUDOE SOE4/P5/E1021 project supported by the European Union through Interreg SUDOE Program and the projects PID2020–113244GA-C22 (funded by MCIN/ AEI /10.13039/501100011033), PID2019–110055RB-C22 (funded by MCIN/ AEI /10.13039/501100011033), PGC2018–093824-B-C44 (funded by MCIN/AEI/ 10.13039/501100011033 and by “ERDF A way of making Europe”). Open Access funding was provided thanks to the CRUE-CSIC agreement with Elsevier