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Background Ultraviolet-B (UV-B) radiation can affect several aspects ranging from plant growth to metabolic regulation. Maca is a Brassicaceae crop native to the Andes growing in above 3500 m of altitude. Although maca has been the focus mainly due to its nutraceutical properties, it remains unknown how maca plants tolerate to harsh environments, such as strong UV-B. Here, we present the first study that reports the physiological responses of maca plants to counteract and recover to repeated acute UV-B irradiation. Results In detail, plants were daily exposed to acute UV-B irradiation followed by a recovery period under controlled conditions. The results showed that repeated acute UV-B exposures reduced biomass and photosynthetic parameters, with gradual senescence induction in exposed leaves, reduction of young leaves expansion and root growth inhibition. Negative correlation between increased UV-B and recovery was observed, with marked production of new biomass in plants treated one week or more. Conclusions A differential UV-B response was observed: stress response was mainly controlled by a coordinated source-sink carbon allocation, while acclimation process may require UV-B-specific systemic defense response reflected on the phenotypic plasticity of maca plants. Moreover, these differential UV-B responses were also suggested by multifactorial analysis based on biometric and physiological data. Electronic supplementary material The online version of this article (10.1186/s12870-019-1755-5) contains supplementary material, which is available to authorized users.

Soil properties and the ability to sustain agricultural production are seriously impaired by salinity. The cultivation of halophytes is seen as a solution to cope with the problem. In this framework, a greenhouse pot experiment was set up to assess salinity response in the perennial C4 species Atriplex halimus, and in the following three cultivars of the annual C3 Atriplex hortensis: green, red, and scarlet. The four genotypes were grown for 35 days with water salinity (WS) ranging from 0 to 360 mM NaCl. Plant height and fresh weight (FW) increased at 360 vs. 0 WS. The stomatal conductance (GS) and transpiration rate (E) were more severely affected by salinity in the C4 A. halimus than in the C3 species A. hortensis. This was reflected in a lower leaf water potential indicating stronger osmotic adjustment, and a higher relative water content associated with more turgid leaves, in A. halimus than A. hortensis. In a PCA including all the studied traits, the GS and E negatively correlated to the FW, which, in turn, positively correlated with Na concentration and intrinsic water use efficiency (iWUE), indicating that reduced gas exchange associated with Na accumulation contributed to sustain iWUE under salinity. Finally, FTIR spectroscopy showed a reduced amount of pectin, lignin, and cellulose under salinity, indicating a weakened cell wall structure. Overall, both species were remarkably adapted to salinity: From an agronomic perspective, the opposite strategies of longer vs. faster soil coverage, involved by the perennial A. halimus vs. the annual A. hortensis cv. scarlet, are viable natural remedies for revegetating marginal saline soils and increasing soil organic carbon.

The anionic surfactant SLES (sodium lauryl ether sulfate) is an emerging contaminant, being the main component of foaming agents that are increasingly used by the tunnel construction industry. To fill the gap of knowledge about the potential SLES toxicity on plants, acute and chronic effects were assessed under controlled conditions. The acute ecotoxicological test was performed on Lepidum sativum L. (cress) and Zea mays L. (maize). Germination of both species was not affected by SLES in soil, even at concentrations (1200 mg kg−1) more than twice higher than the maximum realistic values found in contaminated debris, thus confirming the low acute SLES toxicity on terrestrial plants. The root elongation of the more sensitive species (cress) was instead reduced at the highest SLES concentration. In the chronic phytotoxicity experiment, photosynthesis of maize was downregulated, and the photosynthetic performance (PITOT) significantly reduced already under realistic exposures (360 mg kg−1), owing to the SLES ability to interfere with water and/or nutrients uptake by roots. However, such reduction was transient, likely due to the rapid biodegradation of the surfactant by the soil microbial community. Indeed, SLES amount decreased in soil more than 90% of the initial concentration in only 11 days. A significant reduction of the maximum photosynthetic capacity (Pnmax) was still evident at the end of the experiment, suggesting the persistence of negative SLES effects on plant growth and productivity. Overall results, although confirming the low phytotoxicity and high biodegradability of SLES in natural soils, highlight the importance of considering both acute and nonlethal stress effects to evaluate the environmental compatibility of soil containing SLES residues.

In Mediterranean regions, extreme weather conditions during the growing season may alter grapevine physiology and metabolism, thus modifying the quality of wines. The objective of this study was to investigate the effects of Ascophyllum nodosum treatments on plant physiology and berry metabolism in Vitis vinifera exposed to water stress. The experiment was performed on potted vines subjected to two irrigation regimes (well-watered, WW, and water stressed, WS) both associated with A. nodosum treatments (SWE), compared with control plants (CTRL). Gas exchanges, chlorophyll fluorescence, and water relations were monitored on SWE and CTRL leaves, both in WW and WS vines at three times. Moreover, the quantification of secondary metabolites and their partitioning were performed in berry skins. Plants treated with A. nodosum extract showed higher photosynthesis and stomatal conductance than CTRL in both irrigation regimes and maintained a better plant hydraulic conductivity at the end of the sampling period. In addition, secondary metabolites in berry skins and their partitioning were significantly affected by the treatments in both irrigation regimes. Our results suggest that foliar application of A. nodosum extract may help the acclimation of grapevines to post-veraison water stress, likely improving plant physiological and biochemical performances under environmental constraints.

Cowpea is a crop with great economic, social and food importance in semi-arid regions, but its production is drastically reduced by the water deficit in these regions, requiring better management strategies that allow the crop’s production. This study therefore aimed to evaluate the photosynthetic efficiency and production of cowpea cultivars under deficit irrigation replacement levels. The experiment tested three cowpea genotypes (G1 = ‘BRS Aracé’, G2 = ‘BR 17 Gurguéia’ and G3 = ‘BRS Marataoã’) and four irrigation depths (40, 60, 80 and 100% of ETc), resulting in a 3 x 4 factorial scheme, arranged in randomized complete blocks design with four replicates. During the experiment, the gas exchanges, chlorophyll a fluorescence and production of the cowpea genotypes under deficit irrigation were evaluated. Carbon fixation in the photosynthetic metabolism of cowpea plants was reduced by accentuated water deficit, regardless of the genotype. The low stress severity was indicated by the lack of effects on chlorophyll fluorescence, indicating that the reduction in the rate of carbon assimilation was due to the stomatal effects. The irrigation with 80% of ETc can be used in the cultivation of the respective cultivars, but with small losses in the production. Among the genotypes, ‘BRS Marataoã’ stands out with respect to yield, with higher values for weight of pods and green beans. Resumo O feijão-caupi é uma cultura que apresenta grande importância econômica e sócio-alimentar em regiões semiáridas, no entanto, sua produção é drasticamente reduzida pelo déficit hídrico ocorrente nessas regiões, sendo necessário traçar melhores estratégias de manejo que viabilizem a produção da cultura. Com isso, objetivou-se avaliar a eficiência fotossintética e a produção de genótipos de feijão-caupi sob níveis de reposição da irrigação deficitária. O experimento foi constituído por um estudo de três genótipos de feijão-caupi (G1 = BRS Aracé, G2 = BR 17 Gurgueia e G3 = BRS Marataoã) e quatro lâminas de irrigação (40, 60, 80 e 100% da ETc), que aos combinados resulta em um fatorial 3 x 4, organizado no delineamento em blocos casualizados com quatro repetições. Durante a condução do experimento foram avaliadas as trocas gasosas, fluorescência da clorofila a e de produção dos genótipos de feijão-caupi sob irrigação deficitária. A fixação de carbono no metabolismo fotossintético de plantas de feijão-caupi é reduzida com déficit hídrico acentuado, independente do genótipo. A baixa severidade do estresse foi indicada pela inexistência de efeitos sobre a fluorescência da clorofila, indicando que a redução na taxa de assimilação de carbono se deveu aos efeitos estomáticos. A irrigação com 80% da Etc pode ser utilizada no cultivo das respectivas cultivares, porém com pequenas perdas na produção. Entre os genótipos de feijão, o ‘BRS Marataoã’ destaca-se quanto à produtividade com maiores valores para peso de vagem e grãos verdes.

The effects of prescribed burning in heterogeneous field conditions on Pinus nigra subsp. laricio are still quite unknown. In this perspective, a multidisciplinary approach combining physical fire measurements, physiological and ecological measurements was implemented. Two experiments of prescribed burning were carried out in different locations. First, in a forest of mature P. nigra subsp. laricio in true conditions ; then, in nursery, as a preliminary study to test indicators and obtain information on young individuals.For each experiment, the intensity of prescribed burning was characterized by temperature measurements in and out of the trunk. Physiological monitoring was carried out with the use of several complementary approaches : gas exchange, chlorophyll fluorescence, sap flux and loss of conductance. A survey was also performed on the plot scale (litter mass, botanical) during three years.Since P. nigra subsp. laricio is not studied much, we first tried to evaluate seasonal variations of physiological indicators. Pines showed a significant response to weather, with a decrease in gas exchange with the atmosphere, this behaviour is typical of a water saver strategy. These results have been used as a basis to explain ecophysiological responses of pines to environmental disturbances.Following the prescribed burning, significant differences were observed between the experiment in the nursery and the experiment in the forest. Indicators of vitality used showed no significant effects on mature pines. Young individuals were much more sensitive, suffering severe damages to the trunk and crown, causing the death of some pines.The specific richness and composition of undergrowth vegetation were strongly influenced by short-term prescribed burning and did not return to baseline after three years. The information acquire allowed us to extend knowledge about the physiology and tolerance to hydric and thermal stresses for P. nigra subsp. laricio as well as to provide recommendations to forest managers., Les effets des brûlages dans des conditions hétérogènes de terrain sur les pinèdes à Pinus nigra subsp. laricio sont encore mal connus. Dans cette optique, une approche multidisciplinaire associant des mesures physiques du feu, à un suivi de mesures physiologiques et écologiques a été mise en œuvre. Deux expérimentations de brûlages dirigés ont été réalisées, la première dans une forêt de P. nigra subsp. laricio en conditions réelles sur des individus matures ; la seconde en pépinière a consisté en une étude préliminaire pour tester des indicateurs et obtenir des renseignements sur de jeunes individus.Pour chaque expérimentation, l’intensité du brûlage dirigé a été caractérisée par des mesures de température dans et hors du tronc. Un suivi physiologique a été effectué en se basant sur plusieurs approches complémentaires : échanges gazeux, fluorescence chlorophyllienne, flux de sève et perte de conductance. Un suivi a également été réalisé à l’échelle de la parcelle (masse de litière, botanique) pendant trois ans.Pinus nigra subsp. laricio ayant été peu étudié, nous nous sommes d’abord attachés à évaluer les variations saisonnières des indicateurs physiologiques. Les pins ont montré une réponse significative aux conditions météorologiques, avec une diminution des échanges gazeux avec l’atmosphère, ce qui est caractéristique d’une stratégie de conservation de l’eau lors d’une sécheresse. Les résultats obtenus ont servi de base pour expliquer les réponses écophysiologiques aux perturbations environnementales.Suite aux brûlages dirigés, d’importantes différences ont été observées entre les expérimentations. Les transferts de chaleur ont été plus importants pour les pins de la pépinière que pour ceux en forêt. Les indicateurs de vitalité utilisés ont montré l’absence d’effets significatifs sur des pins matures. Les jeunes individus se sont montrés beaucoup plus sensible, ils ont subi des dommages importants au niveau du tronc et du houppier, provo-quant la mort de certains pins.La richesse spécifique et la composition de la végétation de sous-bois ont été fortement influencées par le brûlage dirigé à court terme, et ne sont pas retournées à l’état initial après trois ans.Les informations obtenues ont permis d’approfondir les connaissances sur la physiologie et la tolérance aux stress hydrique et thermique de P. nigra subsp. laricio. Ces travaux ont également permis de fournir des recommandations pour les gestionnaires forestiers.

The effects of prescribed burning in heterogeneous field conditions on Pinus nigra subsp. laricio are still quite unknown. In this perspective, a multidisciplinary approach combining physical fire measurements, physiological and ecological measurements was implemented. Two experiments of prescribed burning were carried out in different locations. First, in a forest of mature P. nigra subsp. laricio in true conditions; then, in nursery, as a preliminary study to test indicators and obtain information on young individuals.For each experiment, the intensity of prescribed burning was characterized by temperature measurements in and out of the trunk. Physiological monitoring was carried out with the use of several complementary approaches: gas exchange, chlorophyll fluorescence, sap flux and loss of conductance. A survey was also performed on the plot scale (litter mass, botanical) during three years.Since P. nigra subsp. laricio is not studied much, we first tried to evaluate seasonal variations of physiological indicators. Pines showed a significant response to weather, with a decrease in gas exchange with the atmosphere, this behaviour is typical of a drought avoidance strategy. These results have been used as a basis to explain ecophysiological responses of pines to environmental disturbances.Following the prescribed burning, significant differences were observed between the experiment in the nursery and the experiment in the forest. Indicators of vitality used showed no significant effects on mature pines. Young individuals were much more sensitive, suffering severe damages to the trunk and crown, causing the death of some pines.The specific richness and composition of undergrowth vegetation were strongly influenced by short-term prescribed burning and did not return to baseline after three years.The information acquire allowed us to extend knowledge about the physiology and tolerance to hydric and thermal stresses for P. nigra subsp. laricio as well as to provide recommendations to forest managers., Les effets des brûlages dans des conditions hétérogènes de terrain sur les pinèdes à Pinus nigra subsp. laricio sont encore mal connus. Dans cette optique, une approche multidisciplinaire associant des mesures physiques du feu, à un suivi de mesures physiologiques et écologiques a été mise en oeuvre. Deux expérimentations de brûlages dirigés ont été réalisées, la première dans une forêt de P. nigra subsp. laricio en conditions réelles sur des individus matures ; la seconde en pépinière a consisté en une étude préliminaire pour tester des indicateurs et obtenir des renseignements sur de jeunes individus.Pour chaque expérimentation, l’intensité du brûlage dirigé a été caractérisée par des mesures de température dans et hors du tronc. Un suivi physiologique a été effectué en se basant sur plusieurs approches complémentaires : échanges gazeux, fluorescence chlorophyllienne, flux de sève et perte de conductance. Un suivi a également été réalisé à l’échelle de la parcelle (masse de litière, botanique) pendant trois ans.Pinus nigra subsp. laricio ayant été peu étudié, nous nous sommes d’abord attachés à évaluer les variations saisonnières des indicateurs physiologiques. Les pins ont montré une réponse significative aux conditions météorologiques, avec une diminution des échanges gazeux avec l’atmosphère, ce qui est caractéristique d’une stratégie d’évitement de la sécheresse. Les résultats obtenus ont servi de base pour expliquer les réponses écophysiologiques aux perturbations environnementales.Suite aux brûlages dirigés, d’importantes différences ont été observées entre les expérimentations. Les transferts de chaleur ont été plus importants pour les pins de la pépinière que pour ceux en forêt. Les indicateurs de vitalité utilisés ont montré l’absence d’effets significatifs sur des pins matures. Les jeunes individus se sont montrés beaucoup plus sensible, ils ont subi des dommages importants au niveau du tronc et du houppier, provoquant la mort de certains pins.La richesse spécifique et la composition de la végétation de sous-bois ont été fortement influencées par le brûlage dirigé à court terme, et ne sont pas retournées à l'état initial après trois ans.Les informations obtenues ont permis d'approfondir les connaissances sur la physiologie et la tolérance aux stress hydrique et thermique de P. nigra subsp. laricio. Ces travaux ont également permis de fournir des recommandations pour les gestionnaires forestiers.

Forest functionality and productivity are directly related to canopy light interception and can be affected by potential damage from high irradiance. However, the mechanisms by which leaves adapt to the variable light environments along the multilayer canopy profile are still poorly known. We explored the leaf morphophysiological and metabolic responses to the natural light gradient in a pure European beech (Fagus sylvatica L.) forest at three different canopy heights (top, middle and bottom). Structural adjustment through light-dependent modifications in leaf mass per area was the reason for most of the variations in photosynthetic capacity. The different leaf morphology along the canopy influenced nitrogen (N) partitioning, water- and photosynthetic N-use efficiency, chlorophyll (Chl) fluorescence and quali-quantitative contents of photosynthetic pigments. The Chl a to Chl b ratio and the pool of xanthophyll-cycle pigments (VAZ) increased at the highest irradiance, as well as lutein and ?-carotene. The total pool of ascorbate and phenols was higher in leaves of the top and middle canopy layers when compared with the bottom layer, where the ascorbate peroxidase was relatively more activated. The non-photochemical quenching was strongly and positively related to the VAZ/(Chl a + b) ratio, while Chl a/Chl b was related to the photochemical efficiency of photosystem II. Along the multilayer canopy profile, the high energy dissipation capacity of leaves was correlated to an elevated redox potential of antioxidants. The middle layer gave the most relevant contribution to leaf area index and carboxylation capacity of the canopy. In conclusion, a complex interplay among structural, physiological and biochemical traits drives the dynamic leaf acclimation to the natural gradients of variable light environments along the tree canopy profile. The relevant differences observed in leaf traits within the canopy positions of the beech forest should be considered for improving estimation of carbon fluxes in multilayer canopy models of temperate forests.

The aim of this work is to analyze the effects of a) short-term treatments with different concentrations of O 3 (daily 6-hour fumigation with 0, 65, 175 and 300 ppb for 3-4 days); and b) a medium term treatment with O 3 (150 ppb three times a week for thirty days on the whole) and CO 2 (700 ppm) on gas exchange, chlorophyll fluorescence, and peroxidase activity in holm oak (Quercus ilex L.) leaves. The results show that net photosynthesis, transpiration, F V /F M ratio and POD activity were not influenced until an O 3 concentration of 300 ppb was reached. At this threshold, significant alterations in these physiological and biochemical parameters were found. The treatment with +CO 2 +O 3 showed an increase of net photosynthesis suggesting thus an antagonistic effect of CO 2 with regard to O 3 -induced injuries, while CO 2 alone increased photosynthesis and decreased transpiration but induced no effects on F V /F M ratio or peroxidase activity. From out data, holm oak shows a resistance to episodes of photochemical O 3 stress, that in the Mediterranean region can reach peaks of > 100 ppb. This response is likely to be due to the inorpho-anatomic structure of holm oak leaves and their sclerophyllous adaptations. This might leads holm oak to adopt a stress tolerance strategy with regard to leaf response to O 3 , the effects of which cannot be ameliorated by an increase of atmospheric CO 2 .