Light means power: harnessing light spectrum and UV-B to enhance photosynthesis and rutin levels in microtomato plants

Urban vertical agriculture with lighting system can be an alternative green infrastructure to increase local food production irrespective of environmental and soil conditions. In this system, light quality control can improve the plant physiological performance, well as induce metabolic pathways that contribute to producing phenolic compounds important to human health. Therefore, this study aimed to evaluate the influence of RBW (red, blue and white) and monochromatic (red and blue; R and B, respectively) light associated or not with UV-B on photosynthetic performance and phenolic compound production in microtomato fruits cultivated via vertical agriculture. The experimental design adopted was completely randomized, with six replicates illuminated with 300 µmol·m−2·s−1 light intensities (RBW, RBW + UV, B, B + UV, R, and R + UV), 12 h photoperiod, and 3.7 W·m−2 UV-B irradiation for 1 h daily for the physiological evaluations. Twenty-six days after the installation, gas exchange, chlorophyll a fluorescence and nocturnal breathing were evaluated. Fruits in different ripening stages (green, orange, and red) were collected from microtomato plants grown under with different light qualities, to evaluate the physiological performance. The identification and quantification of the phenolic compound rutin was also performed to investigate their metabolic response. This study identified that plants grown under B + UV had high photosynthetic rates (A=11.57 µmol·m−2·s−1) and the fruits at all maturation stages from plants grown under B and B + UV had high rutin content. Meanwhile, the activation of suppressive mechanisms was necessary in plants grown under R because of the high nocturnal respiration and unregulated quantum yield of the non-photochemical dissipation of the photosystem II. These results highlight the importance of selecting light wavelength for vegetable cultivation to produce fruits with a high content of specialized metabolites that influence color, flavor, and health promotion, which is of special interest to farmers using sustainable cropping systems

Effect of nitric oxide in amelioration of arsenic-induced stress in Pistia stratiotes L.(Araceae)

O efeito do óxido nítrico na atenuação do estresse desencadeado pelo arsênio (As) foi avaliado em Pistia stratiotes, sendo o óxido nítrico suprido na forma de nitroprussiato sódico (SNP). As plantas, cultivadas em solução nutritiva, pH 6,5, ½ da força iônica, foram expostas a quatro tratamentos: controle (apenas solução nutritiva); SNP (0,1 mg L-1); As (1,5 mg L-1); As + SNP (1,5 e 0,1 mg L-1, respectivamente). As plantas permaneceram nessas condições por sete dias, para análises de crescimento e absorção de As e nutrientes minerais, e por 24 horas, para análises de alterações metabólicas. A cinética de absorção de As foi analisada, utilizando-se para isso seis concentrações do poluente, nas quais as plantas permaneceram por duas horas: 0,0; 0,25; 0,5; 0,75; 1,0 e 1,5 mg L-1. Os parâmetros de cinética de absorção de As por P. stratiotes indicam que a absorção do metalóide ocorre por transportadores de alta afinidade. O As absorvido foi acumulado nos tecidos vegetais, principalmente na raiz, conferindo a P. stratiotes baixo fator de translocação e o status de possível hiperacumuladora, características que não foram afetadas pela presença de SNP. O acúmulo de As desencadeou uma série de danos, como aumento na produção de espécies reativas de oxigênio (ânion superóxido e peróxido de hidrogênio) e na peroxidação lipídica. Estes danos foram revertidos pelo SNP, que aparentemente atuou diretamente como antioxidante e como molécula sinalizadora, estimulando respostas antioxidantes enzimáticas (catalase, peroxidase e peroxidase do ascorbato) e não enzimáticas (estímulo do ciclo ascorbato-glutationa), o que se refletiu em aumentos na capacidade antioxidante total. Como consequência, o índice de tolerância ao As aumentou na presença de SNP. Os parâmetros fotossintéticos também foram afetados pela presença de As, sendo que os teores de pigmentos cloroplastídicos diminuíram, com exceção dos carotenóides, que apresentaram aumentos em suas concentrações. A presença de SNP restaurou os teores dos pigmentos à níveis normais. A eficiência fotoquímica máxima do FSII e o rendimento quântico do transporte de elétrons também foram afetados negativamente pelo As, enquanto coeficiente de extinção não fotoquímica apresentou incrementos significativos. A assimilação líquida de carbono decresceu significativamente na presença de As, enquanto gs não se alterou e a razão Ci/Ca aumentou, indicando a ocorrência de limitações bioquímicas. A razão ΦFSII/ ΦCO2 foi maior nas plantas expostas ao As. O SNP teve efeito protetor tanto sobre a fluorescência quanto sobre as trocas gasosas, restaurando estes parâmetros à níveis normais. Em relação aos teores de nutrientes minerais, a exposição ao As diminuiu os teores de ferro, magnésio, manganês e fósforo, não tendo afetado os teores de cálcio. Destes nutrientes, apenas os teores de fósforo não retornaram a valores semelhantes ao controle quando o As foi suprido em combinação com SNP. Desta forma o óxido nítrico, suprido na forma de SNP, foi eficaz na atenuação dos danos desencadeados pelo As, agindo tanto como antioxidante direto quanto como molécula sinalizadora.Nitric oxide effect on attenuating the stress triggered by arsenic (As) was evaluated in Pistia stratiotes, being the nitric oxide supplied in the form of sodium nitroprusiate (SNP). The plants were cultivated in nutrient solution, pH 6.5, ½ ion force and exposed to four treatments: control (nutrient solution) SNP (0.1 mg L-1); As (1.5 mg L-1); As + SNP (1.5 and 0.1 mg L-1, respectively). The plants remained in this condition for seven days to the analysis of growth and, As and mineral nutrients uptake and for 24 hours, to the analysis of metabolic changes. The As uptake kinetic was analyzed using six concentrations of this pollutant, in which the plants remained for two hours: 0.0, 0.25, 0.5, 0.75, 1.0 and 1.5 mg L-1. The parameters of As uptake kinetic in P. stratiotes indicate that this metalloid uptake occurs by the high affinity transporters. The absorbed As was accumulated in the vegetal tissues, mainly in the roots, which gave to P. stratiotes a low translocation factor and a status of probably hyperaccumulator, a characteristic that was not affected by SNP presence. The As accumulation triggered many damages, as the increment of reactive oxygen species (superoxide anion and hydrogen peroxide) and lipid peroxidation. These damages were reversed by SNP, which apparently acted directly as antioxidant and as a signalizing molecule, stimulating enzymatic (catalase, peroxidase and ascorbate peroxidase) and non-enzymatic (stimulating the ascorbato-glutathione cycle) antioxidant responses, which reflected in an increase in total antioxidant capacity. As a consequence, As tolerance index increased in the presence of SNP. The photosynthetic parameters were also affected, with the reduction in the chloroplastic pigments concentration in presence of As, except carotenoids that showed an increase in their concentration. The SNP presence restored pigments concentrantion to the normal levels. The maximum photochemical efficiency of PSII and the quantum yield of electron transport were also negatively affected by As, while the non-photechemical quenching (NPQ) presented significant increment. Carbon assimilation (A) decreased significantly in As presence whereas gs did not alter and the Ci/Ca rate increased, indicating biochemical limitations. The ΦFSII/ ΦCO2 rate was higher in plants exposed to As. For the mineral nutrients concentration, As exposition decreased iron, magnesium, manganese and phosphorus concentration, but did not alter calcium concentration. Of these nutrients, only phosphorus concentration did not show similar values than control when As was supplied in combination to SNP. Therefore, nitric oxide, supplied in the form of SNP, was efficient on attenuating damages triggered by As, acting as a direct antioxidant and as a signalizing molecule.Fundação de Amparo a Pesquisa do Estado de Minas Gerai

Cell signaling in response to arsenic: action of nitric oxide on the molecular, biochemical, physiological, ultrastructural level and implications for phytoremediation

O óxido nítrico (NO) é um importante sinalizador celular em condições de estresses bióticos ou abióticos. No presente estudo investigou-se o papel deste sinalizador na resposta de Pistia stratiotes ao arsênio (As). As plantas, cultivadas em solução nutritiva, pH 6,5, 1⁄4 da força iônica, foram expostas a quatro tratamentos, por 24 horas: controle (apenas solução nutritiva); nitroprussiato sódico (SNP doador de NO) (0,1 mg L -1 ); As (1,5 mg L -1 ); As+SNP (1,5 e 0,1 mg L -1 , respectivamente). Para análise de crescimento as plantas permaneceram por três dias nas condições supracitadas. O acúmulo de As por P. stratiotes aumentou a concentração de espécies reativas de oxigênio (ROS), o que teve efeitos danosos sobre a integridade das membranas celulares e sobre vários processos fisiológicos, como fotossíntese, respiração e fotorrespiração. Em relação à fotossíntese, diversos parâmetros foram alterados, desde a concentração de pigmentos até a fixação de carbono, com consequente queda na concentração de sacarose. Comportamento similar foi observado em relação à taxa de fotorrespiração, que também apresentou decréscimos. O processo respiratório, por sua vez, aumentou, provavelmente devido à similaridade química entre arsenato e fosfato, o que comprometeu o status energético da célula. Todos esses efeitos danosos do As se refletiram sobre a estrutura celular de P. stratiotes , provocando a desestruturação do sistema de membranas e o colapso do protoplasto, além de queda dos tricomas. Consequentemente, observou-se queda do crescimento vegetal e baixo índice de tolerância ao poluente. A adição de SNP, no entanto, foi capaz de atenuar os efeitos tóxicos do As, provavelmente através da S-nitrosilação proteica. A adição de SNP manteve a concentração de ROS em níveis similares ao controle e restaurou a taxa fotossintética, a estrutura celular das plantas e a taxa de crescimento. Esses efeitos benéficos do SNP aparentemente são consequências de alterações desencadeadas tanto no metabolismo primário, secundário e antioxidante de P. stratiotes . O SNP aumentou o NPQ e a atividade respiratória, além de inibir a fotorrespiração, o que provavelmente está relacionado com a manutenção da homeostase de ROS e com a geração de esqueletos de carbono para mecanismos de defesa. Essas alterações nos 7 viiiprocessos vegetais foram acompanhadas por mudanças nas concentrações de açúcares, intermediários do ciclo de Calvin e intermediários da fotorrespiração. O SNP também influenciou de forma significativa o metabolismo antioxidante de P. stratiotes exposta ao As, tendo sido observado aumento na atividade de enzimas antioxidantes, como dismutase do superóxido, peroxidase, catalase, peroxidase da glutationa e redutase da glutationa, e alteração a concentração de antioxidantes não enzimáticos, como glutationa, ascorbato e prolina. A glutationa foi particularmente importante na tolerância de P. stratiotes ao As, e parece ter agido tanto como substrato para atividade enzimática quanto para a síntese de fitoquelatinas. O SNP desencadeou ainda alterações nos metabólitos relacionados com a glicólise e com o ciclo dos ácidos tricarboxílicos, além de afetar a concentração de vários polióis e aminoácidos, a maior parte dos quais estão relacionados com o combate ao estresse oxidativo. A adição de SNP permitiu, portanto, a integração dos processos vegetais e o ajuste da maquinaria metabólica de P. stratiotes em resposta ao As, o que resultou na reprogramação do metabolismo antioxidante e alterações no metabolismo primário e secundário, culminando com o aumento da tolerância das plantas ao metaloide.Nitric oxide (NO) is an important cellular signaling molecule involved in the response of plants to biotic and abiotic stress. This study investigated the role of NO in Pistia stratiotes responses to arsenic (As). The plants were cultivated in nutrient solution, pH 6.5, with 1⁄4 of the full ionic strength and exposed to four treatments, for 24 hours: control (nutrient solution) sodium nitroprusside (SNP) (0.1 mg L-1); As (1.5 mg L-1); As + SNP (1.5 and 0.1 mg L-1, respectively). For growth analysis, plants remained for three days in the conditions described above. The accumulation of As by P. stratiotes increased the concentration of reactive oxygen species, which had harmful effects on the integrity of cell membranes and several physiological process, as photosynthesis, respiration and photorespiration. Regarding the photosynthesis, several parameters have changed, including since the pigment concentration until the carbon fixation, with consequent decrease in sucrose concentration.Similar behavior was observed in relation to photorespiration rate, which also decreased. The respiration process increased, probably due to chemical similarity between arsenate and phosphate, which compromised the energy status of the cell. All these harmful effects of As were reflected in the cellular structure of P. stratiotes, causing the disruption of the membranes system, the collapse of the protoplast and fall in trichomes.As a consequence, there was decrease of plant growth and low level of tolerance to the pollutant. The addition of SNP, however, was able to attenuate the toxic effects of the As, probably through protein S-nitrosylation. The addition of SNP remained the concentration of ROS at levels similar to the control and restored the photosynthetic rate, the cellular structure and the growth rate. These beneficial effects of SNP apparently are consequences of changes triggered both in primary, secondary and antioxidant metabolism of P. stratiotes . The SNP increased the NPQ and the respiratory activity, and inhibited photorespiration, which is probably related to the maintenance of ROS homeostasis and the generation of carbon skeletons for defense mechanisms. These changes in plant processes were accompanied by changes in sugar concentrations, Calvin cycle intermediates and intermediates of the photorespiration. The SNP also influenced the antioxidant metabolism of P. 9 ixistratiotes exposed to As and increased the activity of antioxidant enzymes such as superoxide dismutase, peroxidase, catalase, glutathione peroxidase and of glutathione reductase, and altered the concentration of non-enzymatic antioxidants such as glutathione, ascorbate and proline. Glutathione was particularly important in the tolerance of P. stratiotes to As, and appears to have acted both as a substrate for enzyme activity as for the phytochelatin synthesis. The SNP also triggered changes in metabolites related with the glycolysis and the tricarboxylic acid cycle and affected the concentration of various polyols and amino acids, most of which are related to the oxidative stress. The addition of SNP therefore enabled the integration of plant physiological processes and the adjusting the metabolic machinery of P. stratiotes in response to As, resulting in the reprogramming the antioxidant metabolism and changes in primary and secondary metabolism, culminating in the increase in the plant tolerance to the metalloid.Conselho Nacional de Desenvolvimento Científico e Tecnológic

Dispersão de diásporos não mirmecocóricos por formigas: influência do tipo e abundância do diásporo

A mirmecocoria é importante processo para a dinâmica vegetacional em diferentes ecossistemas, principalmente na região neotropical. Entretanto, a relação entre formigas e diásporos não mirmecocóricos é pouco documentada em ambientes da América do Sul. Dessa forma, este estudo teve por objetivos quantificar a taxa de remoção de diásporos não mirmecocóricos em fragmento de Cerrado e verificar se a presença de recursos energéticos e, ou, a abundância dos diásporos são determinantes para sua remoção por formigas. Formigas removeram 19,81% dos diásporos não mirmecocóricos coletados, e a presença de recursos energéticos influenciou significativamente essa remoção, não sendo significativa a relação entre abundância e remoção. Como a maioria dos diásporos coletados não era do tipo carnoso, com pouco ou nenhum recurso energético disponível para formigas, a importância da mirmecofauna para a remoção de diásporos não mirmecocóricos pode estar sendo subestimada

Drought-Induced Mortality: Branch Diameter Variation Reveals a Point of No Recovery in Lavender Species

International audienceIn the context of climate change, determining the physiological mechanisms of drought-induced mortality in woody plants and identifying thresholds of drought survivorship will improve forecasts of forest and agroecosystem die-off. Here, we tested whether continuous measurements of branch diameter variation can be used to identify thresholds of hydraulic failure and physiological recoverability in lavender (Lavandula angustifoliaandLavandulaxintermedia) plants exposed to severe drought. Two parameters of branch diameter variation were tested: the percentage loss of diameter and the percentage loss of rehydration capacity. In two greenhouse experiments with different growth conditions, we monitored variation in branch diameter in the two lavender species exposed to a series of drought/rewatering cycles that varied in drought-stress intensity. Water potential, stomatal conductance, loss of xylem hydraulic conductance, and electrolyte leakage were also measured. We observed that plants were not able to recover when percentage loss of diameter reached maximum values of 21.3% +/- 0.6% during drought, regardless of species and growth conditions. A percentage loss of rehydration capacity of 100% was defined as the point of no recovery, and was observed with high levels of cellular damage as estimated by electrolyte leakage measured at 75.4% +/- 9.3% and occurred beyond 88% loss of xylem hydraulic conductance. Our study demonstrates that lavender plants are not able to recover from severe drought when they have used up their elastic water storage. Additionally, drought-induced mortality in these species was not linked to xylem hydraulic failure but rather to high levels of cell damage. Under extreme drought, death of lavender plants occurs when the water storage of the elastic compartment of the branch is exhausted

Role of glutathione in tolerance to arsenite in Salvinia molesta, an aquatic fern

ABSTRACT In many plant species, tolerance to toxic metals is highly dependent on glutathione, an essential metabolite for cellular detoxification. We evaluated the responses of glutathione metabolism to arsenite (AsIII) in Salvinia molesta, an aquatic fern that has unexplored phytoremediation potential. Plants were exposed to different AsIII concentrations in nutrient solution for 24 h. AsIII caused cell membrane damage to submerged leaves, indicating oxidative stress. There was an increase in the glutathione content and ϒ-glutamylcysteine synthetase enzyme activity in the submerged and floating leaves. The glutathione peroxidase and glutathione sulfotransferase enzymes also showed increased activity in both plant parts, whereas glutathione reductase only showed increased activity in the submerged leaves. These findings suggest an important role for glutathione in the protection of S. molesta against the toxic effects of AsIII, with more effective tolerance responses in the floating leaves

Scots pines colonizing the harsh environment of volcano slopes increased their hydraulic safety margin

International audienceThe ability of trees to survive and naturally regenerate under increasing drought conditions will depend on their capacity to vary key hydraulic and morphological traits that increase drought tolerance. Yet, there has been limited investigation into this variability under recurrent severe drought conditions since the establishment phase. We investigated the hydraulic and leaf trait adjustments of Scots pine trees settled in an abandoned slag quarry by comparing them across three topographic positions inducing contrasted effects on growth. We measured xylem and foliar traits to compare the water status of trees according to tree location and to evaluate the respective risk for xylem hydraulic failure using the soil–plant hydraulic model SurEau. Compared to upslope and downslope trees, slope trees exhibited lower growth, photosynthetic pigment contents, vulnerability to embolism and specific hydraulic conductivity, as well as higher water potential at turgor loss point and midday water potentials. As a consequence, slope trees showed an increase in the hydraulic safety margin and a low level of embolism, compared to downslope and to upslope trees. Additionally, these adjustments induced an increase in the time to hydraulic failure in slope trees compared to downslope and upslope trees under similar drought conditions simulated using the SurEau model. These results suggest a prioritization of hydraulic safety over growth in Scots pine developed in a harsh environment, resulting in a dwarf phenotype

Hydraulic adjustments of Scots pine colonizing a harsh environment on volcano slopes

Abstract The ability of trees to survive and naturally regenerate in increasing drought conditions will depend on their capacity to vary key hydraulic and morphological traits that increase drought tolerance. Despite many studies investigating variability in these drought-tolerant traits, there has been limited investigation into this variability under recurrent severe drought conditions since the establishment phase. We investigated the long-term hydraulic and leaf trait adjustments of Scots pine trees settled in an abandoned slag quarry by comparing them across three different topographic positions inducing contrasted effects on growth and development. We measured xylem and foliar traits to compare the water status of trees according to tree location and to evaluate the respective risk for xylem hydraulic failure using the soil-plant hydraulic model SurEau . Compared to upslope and downslope trees, slope trees exhibited lower growth, vulnerability to embolism, specific hydraulic conductivity and photosynthetic pigment contents, as well as higher water potential at turgor loss point and midday water potentials. The hydraulic adjustments of trees settled on slag slopes reduced the risk for hydraulic failure and thus prevented an increase in embolism compared to downslope and upslope trees. These results suggest a prioritization of hydraulic safety over growth in Scots pine developed in a harsh environment, resulting in a dwarf phenotype

Hydraulic adjustments of Scots pine colonizing a harsh environment on volcano slopes

Abstract The ability of trees to survive and naturally regenerate in increasing drought conditions will depend on their capacity to vary key hydraulic and morphological traits that increase drought tolerance. Despite many studies investigating variability in these drought-tolerant traits, there has been limited investigation into this variability under recurrent severe drought conditions since the establishment phase. We investigated the long-term hydraulic and leaf trait adjustments of Scots pine trees settled in an abandoned slag quarry by comparing them across three different topographic positions inducing contrasted effects on growth and development. We measured xylem and foliar traits to compare the water status of trees according to tree location and to evaluate the respective risk for xylem hydraulic failure using the soil-plant hydraulic model SurEau . Compared to upslope and downslope trees, slope trees exhibited lower growth, vulnerability to embolism, specific hydraulic conductivity and photosynthetic pigment contents, as well as higher water potential at turgor loss point and midday water potentials. The hydraulic adjustments of trees settled on slag slopes reduced the risk for hydraulic failure and thus prevented an increase in embolism compared to downslope and upslope trees. These results suggest a prioritization of hydraulic safety over growth in Scots pine developed in a harsh environment, resulting in a dwarf phenotype