Plants mobilize photosynthates by three transport pathways: apoplastic, symplastic through plasmodesmata (PD), and transcellular. In the flavedo of post-harvest mature lemons, a high level of activity of cell wall-bound invertase (WI), an enzyme associated with transcellular transport of monosaccharides, has been detected. To elucidate whether this high enzymatic activity is related to restricted transport in the symplastic pathway with fruit maturation, the aim of the present work was to compare anatomical and biochemical parameters in peel tissues of immature and mature lemons. Anatomical structure of cell walls, callose deposition, WI activity, and sucrose content were analyzed in peel tissues of immature and mature lemons. The parenchyma of the flavedo tissue of immature lemons presented an elevated number of primary pit fields (PPF). These PPF, associated with PD or cell wall interruptions, had the appearance of a string of beads; however, in mature lemons, the number of PPF was scarce due to callose deposition. WI activity and apoplastic sucrose content increased significantly in the flavedo of mature lemons compared to immature lemons. The present findings lay structural and functional bases relevant to understanding differences between immature and mature lemons, which would help to design agricultural practices in pre- and post-harvest management.

Floating ferns of the genusSalviniahave great potential for phytoremediation of heavy metals. To date, the effect of essential metals on the accumulation and transport of toxic metals by aquatic ferns has not been suitably established. The aim of this study was to compare the ability of floating leaves ofSalvinia minimaandSalvinia rotundifoliaspecies to accumulate Cr from Cr(VI solutions containing very low (0.02 mg L-1) and low (5 mg L-1) Zn concentrations. After 7-day metal-exposure period, results showed that Zn increased Cr accumulation inS. minimaleaves whereas inS. rotundifoliadecreased significantly. Contrarily Zn accumulation did not show great differences between species. This fact may indicate that Zn interfere Cr(VI) uptake byS. rotundifolia. Bioconcentration factor (BCF) and translocation factor (TF) were affected differently by Zn in bothSalviniaspecies. Membrane stability index (MSI) of bothSalviniaspecies was decreased significantly by 5 mg L-1Zn concentration. Zn ions also increased hydrogen peroxide accumulation in fronds ofSalviniaspecies. Total thiols (TT), non-protein thiols (NPT) and protein-bound thiols (PBT) were differentially affected by Cr(VI) and Zn ions. This study provides evidences on the involvement of different mechanisms against Cr(VI)/Zn toxicity inS. minimaandS rotundifoliaspecies.

Photosynthetic characterization of the quinoa cultivar Titicaca grown at the Encalilla site (1995 m asl), a high mountain valley of the Argentinean Northwest, is described in this study.Titicaca cultivar, bred in Denmark from Chilean and Peruvian parenteral lines, is a promising short cycle cultivar and daylength neutral photoperiod.Results showed that maximal photosynthetic CO2 assimilation (Amax) and stomatal conductance (gs) were similar to other quinoa varieties.However, carboxilation capacity and leaf transpiration (E) were significantly higher in Titicaca cultivar compared with other quinoa cultivars grown in the same place.Assimilation of CO2 and stomatal conductance exhibited a strong correlation, like that occurs between (E) and (gs).Light saturation point (LSP) and light compensation point (LCP) were higher in relation to other quinoa cultivars.Grain yield of 2.35 and 2.51 g/plant was recorded and indicating a well adaptation to arid climatic conditions of the Argentinean Northwest region.The highest value of UV protective pigments found in Titicaca will be explained by solar irradiance in the grown area in relation to Denmark conditions.Grain yield, harvest index and some physiological parameters suggested a good adaptation of the Titicaca quinoa cultivar to high mountain valleys of the Argentina Northwest.This means that Titicaca may be considered as a good alternative for farmers in order to get similar production in less time.

We analyzed the effect of pH on Cr(III) accumulation, biomass production, and phenolic profile of Salvinia rotundifolia and Salvinia minima plants grown in the presence of increasing concentrations of CrCl3. Biomass accumulation, metal tolerance index, and photosynthetic pigment contents indicate that Salvinia rotundifolia seems to be more tolerant of Cr(III) than S. minima at different pHs. Increased metal accumulation by Salvinia species under increasing pH could be explained by changes of the protonation status of cell wall functional groups because both the highest and the lowest pH values used in the present study were outside of the levels at which Cr(III) species start to precipitate. The metal translocation factor indicates that in buffered conditions S. rotundifolia tend to retain more Cr(III) in lacinias than S. minima, probably through the involvement of insoluble phenolics. The results of the present study could be useful to the management of solution pH to maximize the removal of Cr(III) by aquatic plants. Environ Toxicol Chem 2019;38:167-176. (c) 2018 SETAC

Introducción y Objetivos: En las provincias argentinas productoras de alcohol se genera anualmente un gran volumen de vinazas. Se ha propuesto que las mismas podrían ser utilizada para el fertirriego de la caña de azúcar u otras especies. Sin embargo, las investigaciones básicas para conocer el efecto de las mismas sobre el suelo, morfología y fisiología de las especies a fertirrigar son escasas en el noroeste argentino. M&M: Se aportan datos sobre el efecto de la vinaza diluida (1:1, 1:5 y 1:10 v/v) sobre la asimilación fotosintética de soja cultivada bajo condiciones semicontroladas (invernáculo). Resultados: La asimilación fotosintética máxima (Amax) se afecta fuertemente en todas las diluciones utilizadas. En la menor dilución (1:1) la Amax disminuye el 35 % respecto al control, mientras que en la dilución 1:10 dicho porcentaje se reduce al 15,9 %. Los cambios en la Amax se correlacionaron con disminuciones en la conductancia estomática, contenido de nitrógeno foliar (Nf) y clorofila total. Los datos de fluorescencia de la clorofila muestran una disminución de Fv/Fm en la dilución 1:1, lo que indicaría un estrés en el fotosistema II (PSII) inducido por la vinaza. Conclusiones: Se concluye que la aplicación de vinaza diluida, afecta el intercambio de gases y que si se la utiliza debería hacerse con diluciones 1:10 o superiores. Se recomienda estudios a largo plazo para conocer el efecto de la vinaza sobre las características fisicoquímicas y biológicas de los suelos, así como la probable acumulación de metales pesados en las plantas fertirrigadas.

The development and fitness of phytophagous insects are tightly linked to the nutritional quality of their host plants and many studies have examined the influence of primary and secondary metabolites of plants and their effects on the development of insects. Herbivore tactics to modify plant metabolic pathways to lower host toxicity need to be better understood as they are critical to a better understanding of herbivore–host plant relationships. To contribute to this end, in this study we analyzed temporal patterns of glucose, sucrose, fructose, and total soluble sugar contents, as well as tannins, phenols, and flavonoids in the mesocarp of fruit of native walnut ( Juglans australis ), uninfested and infested by Anastrepha fraterculus and Ceratitis capitata (sometimes simultaneously in a single fruit). Both fly species are polyphagous tephritids whose larvae feed on a wide variety of hosts. We observed a high correlation between infestation and adult emergence of these two insects which was positive in the case of sugar content and negative in the case of toxic secondary metabolites in fruit. At particular ripening stages, infested fruit contained higher levels of sugars and lower levels of phenols and tannins than non-infested fruit. We discuss the possibility that A. fraterculus and C. capitata , each with different egg-laying strategies, may modify metabolical pathways in the fruit for their own benefit through larval activity with the help of bacteria in their gut. Alternatively, the patterns observed may be simple side effects of larval feeding and associated growth of opportunistic microorganisms.

La vinaza es un efluente que se genera en la obtención de etanol, está constituido en un 90% por agua, su pH es ácido y contiene 10% de compuestos orgánicos e inorgánicos. El enorme volumen de vinaza que se genera anualmente, puede llevar a la contaminación de suelos y cursos de agua en gran escala con el consiguiente riesgo socioeconómico que tal situación puede producir. Una posibilidad para dicha problemática puede ser la utilización de la vinaza para fertirriego de diferentes cultivos. Sin embargo, tal posibilidad requiere evaluar sus efectos sobre las plantas como en los suelos a mediano y largo plazo. En este estudio se evaluó el efecto de diferentes diluciones de vinaza (1:1, 1:5 y 1:10 v/v) sobre el crecimiento y productividad de la soja bajo condiciones semicontroladas. La altura de planta, diámetro de tallo y número de hojas no variaron significativamente respecto al control sin vinaza; mientras el área foliar específica (AFE) y el contenido de nitrógeno foliar si resultaron afectados. El volumen de grano no resultó afectado en todas las diluciones aplicadas; en tanto que, el rendimiento granario solo fue afectado a la menor dilución. Los resultados se discuten en términos del estrés provocado por la vinaza.

El cultivo de la quinoa para la obtención de granos para la alimentación humana ha comenzado a extenderse en la región de los Valles Calchaquíes (Tucumán, Argentina) por arriba de los 2.000 m snm. Tratándose de un cultivo nuevo para dicha región son necesarios los estudios ecofisiológicos y agronómicos para lograr un manejo adecuado de esta nueva alternativa productiva. En este estudio se analiza el efecto de la densidad de siembra sobre la respuesta fotosintética frente a diferentes densidades de flujo fotosintético de fotones (DFFF) estableciéndose los valores de asimilación máxima (A max), punto de saturación lumínica (PSL), punto de compensación lumínica (PCL), eficiencia fotosintética (Ø CO2 ) y respiración nocturna (R n ). Por otro lado, se roporcionan datos relacionados con la asimilación fotosintética neta (A n ), conductancia estomática (g s ), transpiración foliar (T r ), concentración interna de CO 2 (C i ), capacidad de carboxilación (A n /C i ) y eficiencia intrínseca en el uso del agua (EUA i ). Asimismo se brindan datos sobre el contenido de pigmentos fotosintéticos (clorofilas y carotenoides) y otros compuestos protectores (que absorben a los 305 nm). Este estudio demuestra que los parámetros del intercambio de gases están directamente correlacionados con la morfología, anatomía foliar y rendimiento en granos y que la densidad de siembra tiene un efecto directo sobre ellos.

Effects of seasonality and increasing Cr(VI) concentrations on leaf starch-sucrose partitioning, sucrose- and starch-related enzyme activities, and carbon allocation toward leaf development were analyzed in fronds (floating leaves) of the floating fern Salvinia minima. Carbohydrates and enzyme activities of Cr-exposed fronds showed different patterns in winter and summer. Total soluble sugars, starch, glucose and fructose increased in winter fronds, while sucrose was higher in summer ones. Starch and soluble carbohydrates, except glucose, increased under increasing Cr(VI) concentrations in winter fronds, while in summer ones only sucrose increased under Cr(VI) treatment. In summer fronds starch, total soluble sugars, fructose and glucose practically stayed without changes in all assayed Cr(VI) concentrations. Enzyme activities related to starch and sucrose metabolisms (e.g. ADPGase, SPS, SS and AI) were higher in winter fronds than in summer ones. Total amylase and cFBPase activities were higher in summer fronds. Cr(VI) treatment increased enzyme activities, except ADPGase, in both winter and summer fronds but no clear pattern changes were observed. Data of this study show clearly that carbohydrate metabolism is differently perturbed by both seasonality and Cr(VI) treatment in summer and winter fronds, which affects leaf starch-sucrose partitioning and specific leaf area (SLA) in terms of carbon investment.

González, Juan A.; Sebastián E. Buedo; Fernando E. Prado. 2017. “Carac - terización fotosintética en plantas jóvenes y adultas de Alnus acuminata (“aliso del cerro”) en las Yungas (Tucumán, Argentina)”. Lilloa 54 (1). Se estudió la asimilación fotosintética máxima (A max ) en ejemplares jóvenes y adultos de Alnus acuminata así como otras variables relacio - nadas al intercambio de gases como conductancia estomática (g s ), transpiración foliar (T r ) y concentración interna de CO 2 (C i ). También se calculó la eficiencia de carboxilación (A max /C i ) y la eficiencia intrínseca en el uso del agua (EUA i ) así como el contenido de nitrógeno foliar, pigmentos fotosintéticos, área foliar específica (AFE) y masa foliar específica (MFE). A partir de las curvas de asimilación de CO 2 en función de la radiación fotosintéticamente activa (RFA) se determinaron el punto de compensación por luz (PCL), punto saturación por luz (PSL), efi - ciencia fotosintética (Ø CO2 ), factor de curvatura q y tasa máxima de transporte de electrones (ETR max ). Si bien en la zona de estudio el régimen lumínico es homogéneo, los microhabitats donde crecen los ejemplares adultos y jóvenes de “aliso” son diferentes. Así, en los bosques con ejemplares adultos, las plantas crecen expuestas a radiación solar diferencial por efecto de la vecindad entre individuos; mientras que los ejemplares jóvenes crecen más abiertamente sin interferencia por lo que se hallan más expuestos a la radiación solar. Los resultados muestran que en los ejemplares jóvenes la mayoría de los parámetros evaluados fueron más altos que en las ejemplares adultos. Desde el punto de vista ecofisiológico, este estudio pone en evidencia que tanto la asimilación fotosintética, como las estructuras foliares internas de A. acuminata varían con la ontogenia; comportándose como especies “demandantes de luz” los individuos juveniles y como “tolerantes a la sombra” los adultos.

The International Conference on Fluids and Chemical Engineering (FluidsChE 2017) organised by Centre for Excellence for Advanced Research in Fluid Flow (CARIFF), Universiti Malaysia Pahang, Malaysia (FluidsChE 2017) aims to provide a platform to discuss ideas and latest research findings on different disciplines of chemical engineering. 1st FluidsChE 2015 was conducted in Langkawi, Malaysia in November, 2015 which stirred and kindled intellectual minds to make this event a biannual event to disseminate knowledge and findings of chemical engineering fields to the entire world. As an outcome of the event 60+ research articles are published in reputed journals which are in open access for all spectrums of researchers to gain knowledge. Research publications were sectioned into three volumes, volume -1, 2 and 3. First volume was segmented into these disciplines of fluid flow dynamics, distillation technology and absorption / adsorption technology. Second volume consisted of natural resources product lifecycle, polymer technology and pharmaceutical technology. Third volume contains allied fields of chemical engineering. Researchers from different parts of the world contributed to the knowledge pool. Convergence was seen where researchers from different disciplines collaborated for technology solution support for product development with feasible techno economics with prospects for successful commercialization. Keywords: Chemical Engineering, FluidsChe 2017, Malaysia, Cariff, Sabah

González, Juan A.; Sebastián E. Buedo; Marcela Bruno; Fernando E. Prado. 2017. “Quantifying Cardinal Temperaturas in Quinoa (Chenopodium quinoa) Cultivars”. Lilloa 54 (2). Seed germination and plant growth are affected by temperature. This study was conducted to evaluate the effect of temperature on seed germination of ten quinoa cultivars under a temperature gradient between 8 oC and 50 oC. The time course of germination was fitted using a logistic function. Aborted seeds and non-germinated seeds were also analyzed as function of temperature gradient. Cardinal temperatures were estimated by regression of the inverse time to 50% germination (germination rate) against temperature gradient. The minimum (T min ), optimum (T opt ) and maximum (T max ) temperatures for seed germination were determined using both linear (bilinear model) and polynomial (quadratic and cubic models) regressions. Based on T opt estimated from bilinear and cubic models, quinoa seeds can be grouped into two subgroups: one represented by Kancolla, Chucapaca, Kamiri, Robura and Sajama cultivars with values of T opt £ 33 oC, and other represented by CICA, Sayaña, Amilda, Ratuqui and Samaranti with T opt values ? 33 oC, respectively. Percentages of maximum cumu- lative germination calculated from the quadratic model were closely similar to those obtained in germination trials.

González, Juan A., Guillermo O. Martín (h), Marcela A. Bruno, Fernando E. Prado. 2016. “Quínoa (Chenopodium quinoa) crop as fodder supplement in Valles Calchaquíes (Argentinean Northwest)”. Lilloa 53 (1). Quínoa is multipurpose specie that may be utilized as grain for human nutrition or fodder production destined to animal (cows, goats, sheep, llamas, among others) in some places where natural pastures are scarce. Traditionally quinoa is sown by hand and a high plant density was obtained. In order to avoid plants competition it is necessary to clear eliminating a lot of plants. The objective of this study is the evaluation of the eliminated plants for fodder. This paper contributes with data of aerial dry matter (leaves and stems) in 9 quínoa varieties and 1 genotype (landrace) cultivated in Amaicha del Valle (1,995 m asl, Tucumán, Argentina) of 110 days old. Shoot dry matter production oscillated between 7.7 Tn/ha (var. Sajama) to 2.7 Tn/ha (var. Samaranti). Leaf chemical analysis showed and elevated concentration of potassium (K) in all varieties with an oscillation of 8.54 % (Kancolla) to 9.93 % (Samaranti). Other minerals exhibited a low concentration and in general were 3.9 – 5.4 % for N; 0.20-0.34 for P; 2.5 -3.04 for Ca and 0.87Lil loa 53 (1): 74–81, 2016 74 Lil loa 53 (1): 74–81, 2016 75 1.57 for Mg. Organic matter content showed a variation between of 37.7 % (var. Sajama) and 42 % (var. Kancolla). Leaves and stem protein mean content were 15.7 % and 9.9 % respectively. Total fibers content was higher in stem in relation to leaves but the ash content was the opposite. To take into account dry matter production and protein, fibers and minerals content quínoa may be a good complement fodders for animals that take part in livestock production in Valles Calchaquíes.

Contamination of aquatic and terrestrial environments by toxic chromium (Cr) species is a worldwide increasing problem. Cr occurs in the environment mainly as Cr(III) and Cr(VI) species. Cr is an element whose toxic effects depend on its oxidation state. Cr(VI) is highly mobile and toxic to animals and plants. Conversely, Cr(III) is less mobile and less toxic. Cr does not accumulate in plants naturally, but can be absorbed easily from soils and waters. To face the challenge of adverse effects of Cr species in polluted environments, plants must use different mechanisms either to avoid the entry of toxic Cr species or to block their intracellular toxicity. Although it is always claimed that Cr(VI) is more toxic than Cr(III), when the Cr(VI) enters into cells, it is previously reduced to Cr(III) before its toxic effects occur. From this fact could arise an intriguing question on the unquestioned current dogma about the accumulation of toxic Cr(VI) by plants: that is to say, the conversion of the Cr(VI) form to the “less toxic” Cr(III) form is a key tolerance mechanism. In this chapter, we analyze relationships between Cr(VI), Cr(III), and plants which underlying as “a dangerous affair.”

Erazzú, Luis E.; Juan A. González; Sebastián E. Buedo; Fernando E. Pra- do. 2016. “Efectos de la densidad de siembra en Chenopodium quinoa (quinoa). Incidencia sobre variables morfológicas y rendimiento de grano en la variedad CICA cultivada en Amai- cha del Valle (Tucumán – Argentina)”. Lilloa 53 (1). El cultivo de la quinoa ha comenzado a extenderse en el Noroeste Argentino (NOA) y en especial en los Valles Calchaquíes (valles de altura ubicados en el Noroeste de Argentina). La variedad más utilizada es CICA, originaria del Perú, que fuera obtenida a partir de otra denominada Amarilla de Maranganí. Sin embar- go, no se han encontrado antecedentes que expliquen la preferencia de esta variedad sobre otras. Para contribuir al conocimiento del manejo agronómico de esta variedad se estudió el efecto de la densidad de siembra sobre la morfología y particularmente sobre el rendimiento en granos. Las experiencias se realizaron en una localidad de los Valles Calchaquíes (Amaicha del Valle, Tucumán, Argentina) a 1.995 m sobre el nivel del mar. Los métodos utilizados para la siembra fueron por golpe, realizado manualmente (“CGo”, CICA separadas) y a chorri- llo, con maquina sembradora (“CCh”, CICA juntas). Con éstos se lograron densidades de plan- tas diferentes: 4,2 y 27,9 plantas/metro lineal respectivamente. Tanto la altura de las plan- tas, diámetro de tallo, área foliar específica (AFE), nitrógeno y fósforo foliar y el rendimiento en granos (kg/ha) fue mayor en el primer tratamiento. El análisis de las clases diamétricas de los granos obtenidos reveló que ambos tratamientos producen casi un 65% de granos cuyo diámetro es ? 1,41 mm. Sin embargo, en el tratamiento “CGo” aumenta la proporción de granos cuyos diámetros son ? a 1,68 mm. Este último dato es importante pues los granos con mayor diámetro tienen mayor aceptación en los mercados. En general, el rendi- miento en granos fue de 5.389 kg/ha y 3.049 kg/ha para los tratamientos “CGo” y “CCh”, respectivamente. Estos valores de rendimiento en grano se hallan incrementados con respec- to a aquellos que se obtienen en las zonas andinas y muy próximas a los que se informan para otras condiciones ambientales, como por ejemplo en Europa

The effect of cadmium on roots of four citrus rootstocks was studied to assess the relationships between oxidative stress, carbohydrates, phenolics and antioxidant responses. Swingle citrumelo (SC), Rangpur lime (RL), Troyer citrange (TC) and Volkamer lemon (VL) genotypes were exposed to 0, 5 and 10 µM Cd over 7 days, after which Cd accumulation was markedly higher in roots compared with stems and leaves. Malondialdehyde (MDA) and lipoxygenase (LOX) activity increased in Cd-treated SC and RL roots, suggesting that a lipid peroxidation is the main driver of plasma membrane damage. In contrast, in TC and VL genotypes, LOX-mediated lipid peroxidation does not appear to play a key role in Cd-induced lipid peroxidation, but H2O2 accumulation seems to be responsible of less plasma membrane damage. Catalase (CAT), superoxide dismutase (SOD) and guaiacol and syringaldazine peroxidases (G-POD and S-POD respectively) were differentially affected by Cd. Lipid profile and ATPase-dependant proton extrusion indicated higher disfunctionalities of root plasma membrane in SC and RL genotypes than in TC and VL genotypes. Differences in carbohydrates and phenolic compounds were also observed. Histochemical analysis of G-POD activity and lignin and suberin deposition revealed differences among genotypes. A model to explain the relationships among carbohydrates, soluble phenolics, lipid peroxidation and H2O2 accumulation in Cd-exposed roots was proposed.

In plants of Salvinia rotundifolia and Salvinia minima the effect of two Cr(VI) concentrations (5 and 20 mg L-1) applied for 7 days was assessed by measuring changes in biomass, photosynthetic pigments, Cr accumulation, malondialdehyde (MDA), membrane stability index (MSI), thiols (TT, NPT and PBT), and phenolics (SP and IP). Biomass in S. minima was decreased at highest Cr(VI) concentration, but there were no changes in S. rotundifolia. Metal accumulation was different in both species. S. minima accumulates more metal in fronds, but S. rotundifolia accumulates more metal in lacinias. Results also showed that S. minima translocates more Cr to fronds than S. rotundifolia, but at the whole plant level higher accumulation occurred in this last. Tolerance index (Ti) was higher in S. rotundifolia. Chl b and carotenoids were decreased only upon exposure to high Cr(VI) concentration in both species. Cr(VI) treatment did not enhance MDA accumulation. Cr exposure had no impact on MSI values when comparing with Cruntreated values. Thiols in fronds and lacinias showed different distribution patterns between species. IP and NPT were higher in S. rotundifolia lacinias that accumulate more Cr than S. minima lacinias. Whilst SP and NPT were higher in S. minima fronds compared with S. rotundifolia ones. This may indicate that these species can cope with Cr(VI) toxicity, either through metal complexation and/or metal reduction or by the scavenging of ROS derived from Cr-induced oxidative stress. Based on Cr accumulation and biomass production, S. rotundifolia seems more suitable to remove Cr(VI) from polluted waters. (C) 2016 Elsevier B.V. All rights reserved.

Salvinia minima is a widely distributed floating fern that bioaccumulates high concentrations of heavy metals and is a promising species for Cr(VI) removal from polluted waters. Metal bioaccumulation efficiency of aquatic plants can be affected by different factors such as surrounding pH and metal concentration. In this study we investigated the effect of solution pH on the biosorption and reduction of Cr(VI) in living plants of S. minima under both pH-stat (buffered) and pH-shift (unbuffered) conditions. Plants were exposed to 0, 5 and 20 mgL(-1) Cr(VI) concentrations for 7 days under controlled conditions at pH 4.0, 6.0 and 7.6. Cr(VI) was determined using 1,5-diphenylcarbazide in presence and absence of KMnO4. Cr(III) concentration was estimated as the difference between Cr-total [Cr(VI) + Cr(III)] (with KMnO4) and Cr(VI) (without KMnO4) concentrations. Metal biosorption was significantly higher in acid buffered solution than in unbuffered solution, but the biosorption pattern was different indicating that solution pH could be a key factor controlling the removal of Cr(VI) by S. minima. The pH of acid unbuffered Cr(VI)-containing solutions was significantly increased during Salvinia growth. Contrarily no significant changes of pH were observed in unbuffered solutions without Cr(VI). Reduction of Cr(VI) to Cr(III) was significantly higher at lower pH. Visual symptoms of Cr(VI)-induced damage were less evident at lower pH. Results demonstrated that S. minima can survive and remove Cr(VI) at low pH values. This work indicates that selection of suitable aquatic macrophytes for potential application in heavy metal phytoremediation requires an additional focus regarding interactions among metal, solution pH, and plant performance. (C) 2014 Elsevier B.V. All rights reserved.

Seasonal variations of chloroplast thylakoids and plasma membrane ultrastructure and changes in some biochemical parameters (e.g., metal accumulation, photosynthetic pigments, carbohydrates, lipid peroxidation, and electrolyte leakage) were studied in fronds of Salvinia minima plants exposed to increasing concentrations of Cr(VI) in both winter and summer. Disorganization of stacked (grana) and unstacked (stroma lamellae) thylakoids was greater in winter chloroplasts than in summer chloroplasts. Plasma membrane was less affected than thylakoids. Photosynthetic pigments, lipid peroxidation, soluble sugars, and starch were affected differently in winter and summer. Our results suggest that much greater ultrastructural alterations and changes in metabolite levels occurring in winter fronds are produced by higher oxidative stress resulting from the interactive effect between low temperature, low solar irradiance, and Cr(VI) toxicity, rather than from metal accumulation per se. Seasonal differences occurring in chloroplast ultrastructure and metabolite concentrations were discussed in relation to metabolic implications. Evaluated parameters represent a relevant approach to enhance knowledge on performance and fitness of plants exposed to heavy metals under fluctuating environmental conditions. This work also indicates that selection of suitable macrophytes to remove Cr(VI) requires an additional analyzing focus on structural and metabolic interactions that occur in plants exposed to heavy metals in contrasting seasons.