Integrated Ca, Mg, Cu, and Zn supply upregulates leaf anatomy and metabolic adjustments in Eucalyptus seedlings.

Adaptive responses to abiotic stresses such as soil acidity in Eucalyptus-the most widely planted broad-leaf forest genus globally-are poorly understood. This is particularly evident in physiological and anatomical disorders that inhibit plant development and wood quality. We aimed to explore how the supply of Ca and Mg through liming (lime), combined with Cu and Zn fertilization (CZF), influences physiological and anatomical responses during Eucalyptus grandis seedlings growth in tropical acid soil. Therefore, related parameters of leaf area and leaf anatomy, stomatal size, leaf gas exchange, antioxidant system, nutrient partitioning, and biomass allocation responses were monitored. Liming alone in Eucalyptus increased specific leaf area, stomatal density on the abaxial leaf surface, and Ca and Mg content. Also, Eucalyptus exposed only to CZF increased Cu and Zn content. Lime and CZF increased leaf blade and adaxial epidermal thickness, and improved the structural organization of the spongy mesophyll, promoting increased net CO2 assimilation, and stomatal conductance. Fertilization with Ca, Mg, Cu, and Zn positively affects plant nutrition, light utilization, photosynthetic rate, and antioxidant performance, improving growth. Our results indicate that lime and CZF induce adaptive responses in the physiological and anatomical adjustments of Eucalyptus plantation, thereby promoting biomass accumulation.

Mechanisms of Mucor sp. CM3 isolated from the aquatic macrophyte Eichhornia crassipes (Mart.) Solms to increase cadmium bioremediation.

Bioremediation of toxic metals is a feasible and low-cost remediation tool to reduce metal contamination. Plant-fungus interactions can improve this technique. Eichhornia crassipes (Mart.) Solms is a macrophyte reported to bioremediate contaminated water. Thus, the present study aimed to isolate endophytic fungi from E. crassipes, select a highly cadmium (Cd) tolerant isolate and evaluate its bioremediation potential. This was evaluated by (1) the fungus tolerance and capacity to accumulate Cd; (2) Cd effects on cell morphology (using SEM and TEM) and on the fungal antioxidant defense system, as well as (3) the effect on model plant Solanum lycopersicum L. cultivar Calabash Rouge, inoculated with the endophyte fungus and exposed to Cd. Our results selected the endophyte Mucor sp. CM3, which was able to tolerate up to 1000 g/L of Cd and to accumulate 900 mg of Cd/g of biomass. Significant changes in Mucor sp. CM3 morphology were observed when exposed to high Cd concentrations, retaining this metal both in its cytoplasm and in its cell wall, which may be linked to detoxification and metal sequestration mechanisms related to the formation of Cd-GSH complexes. In addition, Cd stress induced the activation of all tested antioxidant enzymes - superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR) - in this endophytic fungus. Moreover, when inoculated in tomato plants, this fungus promoted plant growth (in treatments without Cd) and induced an increased metal translocation to plant shoot, showing its potential to increase metal bioremediation. Therefore, this study indicates that the isolated endophyte Mucor sp. CM3 can be applied as a tool in different plant conditions, improving plant bioremediation and reducing the environmental damage caused by Cd, while also promoting plant growth in the absence of contaminants.

New insights into cadmium tolerance and accumulation in tomato: Dissecting root and shoot responses using cross-genotype grafting.

Cadmium (Cd) is one of the most threatening soil and water contaminants in agricultural settings. In previous studies, we observed that Cd affects the metabolism and physiology of tomato (Solanum lycopersicum) plants even after short-term exposure. The objective of this research was to use cross-genotype grafting to distinguish between root- and shoot-mediated responses of tomato genotypes with contrasting Cd tolerance at the early stages of Cd exposure. This study provides the first report of organ-specific contributions in two tomato genotypes with contrasting Cd tolerance: Solanum lycopersicum cv. Calabash Rouge and Solanum lycopersicum cv. Pusa Ruby (which have been classified and further characterized as sensitive (S) and tolerant (T) to Cd, respectively). Scion S was grafted onto rootstock S (S/S) and rootstock T (S/T), and scion T was grafted onto rootstock T (T/T) and rootstock S (T/S). A 35 µM cadmium chloride (CdCl2) treatment was used for stress induction in a hydroponic system. Both shoot and root contributions to Cd responses were observed, and they varied in a genotype- and/or organ-dependent manner for nutrient concentrations, oxidative stress parameters, antioxidant enzymes, and transporters gene expression. The findings overall provide evidence for the dominant role of the tolerant rootstock system in conferring reduced Cd uptake and accumulation. The lowest leaf Cd concentrations were observed in T/T (215.11 µg g-1 DW) and S/T (235.61 µg g-1 DW). Cadmium-induced decreases in leaf dry weight were observed only in T/S (-8.20%) and S/S (-13.89%), which also were the only graft combinations that showed decreases in chlorophyll content (-3.93% in T/S and -4.05% in S/S). Furthermore, the results show that reciprocal grafting is a fruitful approach for gaining insights into the organ-specific modulation of Cd tolerance and accumulation during the early stages of Cd exposure.

Leaf 13C and 15N composition shedding light on easing drought stress through partial K substitution by Na in eucalyptus species.

This work aimed to investigate the partial K-replacement by Na supply to alleviate drought-induced stress in Eucalyptus species. Plant growth, leaf gas exchange parameters, water relations, oxidative stress (H2O2 and MDA content), chlorophyll concentration, carbon (C) and nitrogen (N) isotopic leaf composition (δ13C and δ15N) were analyzed. Drought tolerant E. urophylla and E. camaldulensis showed positive responses to the partial K substitution by Na, with similar dry mass yields, stomatal density and total stomatal pore area relative to the well K-supplied plants under both water conditions, suggesting that 50% of the K requirements is pressing for physiological functions that is poorly substituted by Na. Furthermore, E. urophylla and E. camaldulensis up-regulated leaf gas exchanges, leading to enhanced long-term water use efficiency (WUEL). Moreover, the partial K substitution by Na had no effects on plants H2O2, MDA, δ13C and δ15N, confirming that Na, to a certain extent, can effectively replace K in plants metabolism. Otherwise, the drought-sensitive E. saligna species was negatively affected by partial K replacement by Na, decreasing plants dry mass, even with up-regulated leaf gas exchange parameters. The exclusive Na-supplied plants showed K-deficient symptoms and lower growth, WUEL, and δ13C, besides higher Na accumulation, δ15N, H2O2 and MDA content.

Tolerance of tomato to cadmium-induced stress: analyzing cultivars with different fruit colors.

The objective of the present study was to assess the response of tomato cultivars with different fruit colors to exposure to increasing Cd levels in the substrate by measuring the impacts of Cd on the oxidative stress indicators and physicochemical features of fruits, as well as plant development and yield components. A completely randomized experiment in a 3 × 3 factorial design [tomato cultivar (which produces purple, red, or white fruits) vs Cd level in the substrate (0, 3.6, or 12 mg kg-1)] was performed. The cultivation of plants in substrate containing 3.6 mg kg-1 Cd did not affect yield, but fruits exhibited nonpermissive Cd concentrations in both peel and mesocarp across all cultivars. By contrast, yield was decreased in plants with red and white fruits after their cultivation in substrate containing 12 mg kg-1 Cd, while the productivity of plants with purple fruits was maintained under such conditions. The hydrogen peroxide content in the fruit mesocarp depended only on cultivar. However, an increased lipid peroxidation level was detected in the mesocarp of purple fruits at the highest Cd concentration. No parameters of fruit quality [i.e., diameter, length, °Brix, pH, titratable acidity, color (L*, a*, and b*), and concentrations of lycopene and ß-carotene in mesocarp] were affected by long-term exposure to Cd at 12 mg kg-1. In conclusion, the results of this study suggested that the potential Cd side effects on diverse tomato quality features can be buffered at the fruit level because these features were maintained at the usual values despite high Cd concentrations in tomato peel and pulp. Moreover, these buffering mechanisms are independent of lycopene and ß-carotene concentrations in fruit peel, since the three tomato cultivars that were evaluated in the present study (white fruits, possessing no or negligible concentrations of these carotenoids, and red and purple tomato, possessing high lycopene and ß-carotene concentrations) were able to sustain several fruit quality parameters after long-term exposure to high Cd concentrations in the substrate.

Unraveling the mechanisms controlling Cd accumulation and Cd-tolerance in Brachiaria decumbens and Panicum maximum under summer and winter weather conditions.

We evaluated the mechanisms that control Cd accumulation and distribution, and the mechanisms that protect the photosynthetic apparatus of Brachiaria decumbens Stapf. cv. Basilisk and Panicum maximum Jacq. cv. Massai from Cd-induced oxidative stress, as well as the effects of simulated summer or winter conditions on these mechanisms. Both grasses were grown in unpolluted and Cd-polluted Oxisol (0.63 and 3.6 mg Cd kg-1 soil, respectively) at summer and winter conditions. Grasses grown in the Cd-polluted Oxisol presented higher Cd concentration in their tissues in the winter conditions, but the shoot biomass production of both grasses was not affected by the experimental conditions. Cadmium was more accumulated in the root apoplast than the root symplast, contributing to increase the diameter and cell layers of the cambial region of both grasses. Roots of B. decumbens were more susceptible to disturbed nutrients uptake and nitrogen metabolism than roots of P. maximum. Both grasses translocated high amounts of Cd to their shoots resulting in oxidative stress. Oxidative stress in the leaves of both grasses was higher in summer than winter, but only in P. maximum superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities were increased. However, CO2 assimilation was not affected due to the protection provided by reduced glutathione (GSH) and phytochelatins (PCs) that were more synthesized in shoots than roots. In summary, the root apoplast was not sufficiently effective to prevent Cd translocation from roots to shoot, but GSH and PCs provided good protection for the photosynthetic apparatus of both grasses.

Cadmium toxicity degree on tomato development is associated with disbalances in B and Mn status at early stages of plant exposure.

Cadmium (Cd) toxicity is frequently coupled to its accumulation in plants, but not always the highest Cd concentration triggers the worst damages, indicating that additional events influence the magnitude of Cd side-effects. We investigated the early mechanisms behind the differential Cd-induced impacts on plant development of four tomato accessions with contrasting tolerance to Cd toxicity. At organ level, the highest Cd concentration was not associated with the largest biomass losses. In leaves, changes in superoxide dismutase and catalase activities were not related to differences in Cd concentration, which was unable to provoke H2O2 overproduction on the sixth day of plant exposure to this metal. Further investigation in the mineral profile revealed that magnitude of Cd toxicity depends probably on synergic effects from increased B status, in addition to the own Cd accumulation. Furthermore, disbalances in Mn status (i.e., excess in leaves and deficiency in roots) may enhance Cd toxicity degree. According to data, however, the low magnesium (Mg) status can be linked to tomato tolerance against Cd toxicity. In conclusion, the tomato tolerance degree under short-Cd exposure depends on actively, finely regulation of mineral homeostasis that results in different development of plant organs. The better understanding on the mode of action of Cd toxicity in plants can help in the establishment of strategies to mitigate its impacts on crop yield.

Proteomic analysis of mature barley grains from C-hordein antisense lines.

Hordeins are the major storage proteins in barley grains and are responsible for their low nutritional quality. Previously, antisense C-hordein barley lines were generated and were shown to contain a more balanced amino acid composition and an altered storage protein profile. In the present study, a proteomic approach that combined two-dimensional gel electrophoresis (2-DE) and mass spectrometry was used to (1) identify the changes in the protein profile of non-storage proteins (salt soluble fraction) in antisense C-hordein barley lines (L1, L2 and L3) and (2) map the differentially expressed proteins compared to the non-transgenic control line (Hordeum vulgare cv. Golden Promise). Moreover, the changes in the proteins were correlated with the more balanced amino acid composition of these lines, with special attention to the lysine content. The results showed that suppression of C-hordein expression does not exclusively affect hordein synthesis and accumulation. The more balanced amino acid composition observed in the transgenic lines L1, L2 and L3 was an indirect result of the profound alterations in the patterns of the non-storage proteins. The observed changes included up-regulated expression of the proteins involved in stress and detoxification (L1), defence (L2 and L3), and storage globulins (L1, L2 and L3). To a lesser extent, the proteins involved in grain metabolism were also changed. Thus, the increased essential amino acids content results from changes in distinct protein sources among the three antisense C-hordein lines analyzed, although the up-regulated expression of lysine-rich proteins was consistently observed in all lines.

Efeitos de tratamentos térmicos aplicados sobre frutas cítricas armazenadas sob refrigeração / Effects of thermal treatments applied on citric fruits under cold storage

Foram aplicados tratamentos térmicos em laranja "Valência", tangor "Murcott" e lima ácida "Tahiti" armazenadas em baixa temperatura e avaliados os efeitos na redução de injúrias pelo frio e sobre outras características bioquímicas. Os seguintes tratamentos foram aplicados: T1: frutas armazenadas a 1°C (Controle); T2: aquecimento rápido das frutas em água quente a 53°C, durante 3 minutos, sendo, em seguida, armazenadas a 1°C; T3: aquecimento lento das frutas em câmara regulada para 37°C, por 2 dias, com posterior armazenamento a 1°C; e T4: aquecimento intermitente em ciclos de 6 dias a 1°C + 1 dia a 25°C. As frutas foram armazenadas durante 90 dias a 1°C e 90-95 por cento de Umidade Relativa (UR), sendo avaliadas a cada 15 dias. Além da incidência dos danos, foram avaliadas também as atividades das enzimas antioxidativas (catalase, glutationa redutase e ascorbato peroxidase). A lima ácida "Tahiti" e o tangor "Murcott" suportaram até 90 dias de armazenamento a 1°C com aquecimento intermitente, não apresentando danos pelo frio. No tratamento controle (armazenamento contínuo a 1°C), os danos pelo frio surgiram aos 30 dias de armazenamento para a lima "Tahiti" e aos 45 dias para o tangor "Murcott". Em laranjas "Valência", as injúrias pelo frio surgiram aos 45 dias de armazenamento, sendo significativamente menores no condicionamento térmico. Os efeitos dos tratamentos térmicos no aumento da resistência das frutas ao frio podem estar relacionados com a atividade das enzimas antioxidativas. Para a laranja "Valência", os tratamentos térmicos, aplicados na forma de condicionamento térmico ou aquecimento intermitente, reduzem as injúrias pelo frio e podem prolongar a conservação das frutas a 1°C e 90-95 por cento UR. Para tangor "Murcott" e lima "Tahiti", o aquecimento intermitente é o tratamento mais eficiente para a redução de injúrias pelo frio e para o aumento na capacidade de armazenamento.

In the present study thermal treatments on,'Valência' orange, 'Murcott' tangor and 'Tahiti' (temperature conditioning and intermittent warming) were applied lime. The following treatments were applied: T1: Fruits stored at 1°C (Controls); T2: Fast heating of the fruits in hot water at 53°C for 3 minutes and stored at 1°C; T3: Slow heating of the fruits in camera regulated at 37°C for 2 days, with subsequent storage at 1°C; and T4: Intermittent heating in cycles of 6 days at 1°C + 1 day at 25°C. Fruits were stored under low temperature (1°C) and 90-95 percent relative humidity (RH) during 90 days. Chilling injury incidence and changes in physical-chemical characteristics were evaluated every 15 days. Activity of catalase, glutathione reductase and ascorbate peroxidase was also determined. Intermittent warming was more efficient than temperature conditioning to reduce chilling injury. 'Tahiti' lime and 'Murcott' tangor supported up to 90 days of intermittent warming stored at 1°C, while control fruits showed chilling injury after 30 days ('Tahiti' lime) and 45 days ('Murcott' tangor). 'Valência' orange was affected by chilling injury after 45 days of cold storage, and temperature conditioning has caused lower incidence of this disorder. The effect of thermal treatments can be related to the activity of antioxidant enzymes. For ´Valência" orange, thermal treatments, applied as thermal conditioning or intermittent heating, reduce injuries caused by cold and can lengthen the conservation of fruits at 1°C and 90-95 percent RH. The intermittent heating is the most efficient treatment to reduce injuries caused by cold and increase at storage capacity of the 'Murcott' tangor and 'Tahiti' lime.