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The study aimed to verify the water stress indicators of garlic (Allium sativum L.) submitted to water deficit levels, simulating the effects of possible climatic changes. Considering that A. sativum is a crop known worldwide for its medicinal, culinary properties and applications in the ecological management of agricultural pests and, knowing that the planet is undergoing constant climatic changes, this study becomes essential to understand the influence of these changes on this species cultivation. The treatments were established with water conditions of 100, 75, 50, and 25% of the pot capacity (PC). According to the pot capacity, three bulbils were planted per pot (5 L) containing Plantmax® substrate, irrigated every two days. During the first and last week of the greenhouse treatments, the chlorophyll index was evaluated using a porometer with a seven-day interval between the analysis. The first analysis was performed in the first week of water stress and the last one in the last days of stress. Garlic plants showed sensitivity to water deficit, resulting in lower conductance and transpiration compared to treatments 50% and 75% water deficit, apparently without causing changes in production. In view of the results of this study, it is concluded that Allium sativum L. will not be totally harmed by the climate changes expected in the future according to atmospheric changes in the region of Laranjeiras do Sul.

Climate change can cause imbalances in plants. Baccharis trimera is a specie usually found in harsh conditions and has medicinal and agricultural properties. Thus, this study aimed to evaluate the biochemical and physiological responses of this plant under water restriction (WR) levels. B. trimera samples were identified and collected in Erechim/RS and propagated in a greenhouse. When acclimated, they were subjected to 0, 25, 75 and 100% WR, determined according to the water saturation in the soil by capillary action. After 30 days of treatment, the physiological responses: growth, and fresh and dry biomass; and the biochemical responses: activity of superoxide dismutase (SOD), guaiacol peroxidase (GP) and ascorbate peroxidase (APX) enzymes, proline, protein and hydrogen peroxide content, and lipid peroxidation, were determined. Data were submitted to regression analysis and Pearson correlation. The WR of 27.37%, on average, induced an increase in physiological parameters, but the root growth was impaired in conditions above 50% of WR. With the increase in WR there was an increase in the activity of SOD in the shoot and APX in the root. In low WR conditions, proline contents were maintained. Therefore, with low levels of WR, around 27%, B. trimera has increase in root growth and root and shoot biomass. Proline, and SOD and APX activity are a pathway that scavenging the stress generated by WR on B. trimera. El cambio climático puede provocar desequilibrios en las plantas. Baccharis trimera es una especie que se encuentra a menudo en condiciones adversas y tiene propiedades medicinales y agrícolas. Así, el objetivo fue evaluar las respuestas bioquímicas y fisiológicas de esta planta a niveles de restricción de agua (RA). Se identificaron y recolectaron muestras de B. trimera en Erechim - RS y se propagaron en un invernadero. Una vez aclimatados, fueron sometidos a 0, 25, 75 y 100% de RA, determinado según la saturación de agua en el suelo por capilaridad. Después de 30 días de tratamiento, se determinaron las respuestas fisiológicas: crecimiento y biomasa fresca y seca; y respuestas bioquímicas: actividad de las enzimas superóxido dismutasa (SOD), guayacol peroxidasa (GP) y ascorbato peroxidasa (APX), prolina, contenido de peróxido de hidrógeno y proteínas y peroxidación de lípidos. Los datos se sometieron a análisis de regresión y correlación de Pearson. La RA media de 27,37% indujo un aumento en los parámetros fisiológicos evaluados, pero el crecimiento de las raíces se vio afectado en condiciones de RA superiores al 50%. Con el aumento de RA hubo un aumento en la actividad de las enzimas SOD en el parte aérea y de APX en la raíz. En condición de RA baja, se verificó el mantenimiento del contenido de prolina. Por lo tanto, con niveles bajos de RA, alrededor del 27%, B. trimera tiene un aumento en el crecimiento de las raíces y en la biomasa de parte aérea y raíces. La prolina, SOD y APX son una vía de eliminación del estrés generado por la RA en B. trimera. Alterações climáticas podem causar desequilíbrios nas plantas. Baccharis trimera é uma espécie frequentemente encontrada em condições adversas e apresenta propriedades medicinais e para uso na agricultura. Assim, objetivou-se avaliar as respostas bioquímicas e fisiológicas desta planta em níveis de restrição de água (RA). Amostras de B. trimera foram identificadas e coletadas em Erechim - RS e propagadas em casa de vegetação. Quando aclimatadas foram submetidas a 0, 25, 75 e 100% de RA, determinada de acordo com a saturação de água no solo por capilaridade. Após 30 dias de tratamento foram determinadas respostas fisiológicas: crescimento e biomassa fresca e seca; e respostas bioquímicas: atividade de enzimas superóxido dismutase (SOD), guaiacol peroxidase (GP) e ascorbato peroxidase (APX), conteúdo de prolina, proteína e peróxido de hidrogênio, e peroxidação de lipídeos. Os dados foram submetidos a análises de regressão e correlação de Pearson. A RA média de 27,37% induziu aumento nos parâmetros fisiológicos avaliados, porém o crescimento das raízes foi prejudicado em condições de RA acima de 50%. Com o aumento na RA houve o aumento na atividade das enzimas SOD na parte aérea e de APX na raiz. Em condição de baixa RA verificou-se a manutenção do conteúdo de prolina. Portanto, com baixos níveis de RA, em torno de 27%, B. trimera tem aumento no crescimento de raiz e na biomassa da parte aérea e raiz. Prolina, SOD e APX são uma via de eliminação do estresse gerado pela RA em B. trimera.

The objective of this work was to evaluate peroxidase activity and protein concentration in the defence system expression of common bean Phaseolus vulgaris L., submitted to different potencies of homeopathic preparations. The treatments were composed by: Arsenicum album, Staphisagria, Silicea and Sulphur, in the 6, 12 and 18 CH potencies, compared to the controls. The bean seeds were sown in pots which were kept in a greenhouse and the treatments were applied to them at 1% in distilled water since the sowing day, with intervals of 15 days until the R7 stage. The first evaluation was performed at 15 e 60 days after sowing, after artificial mechanical damage. Protein concentration and the activity of guaiacol peroxidase (POD) and ascorbate peroxidase (APX) enzymes were determined. Differences between treatments and controls were estimated by Glass Delta effect size analysis. Staphisagria 12CH induced greater increase in protein concentration on bean leaves. The Induction on APX and POD activities were observed in leaves treated with Sulphur in all tested potencies. The Glass Delta effect showed undulatory behaviour, sometimes acting positively, sometimes negatively, throughout all evaluations. Homeopathic preparations have the potential to induce biochemical defence mechanisms in beans, acting as resistance elicitors. El objetivo de este trabajo fue evaluar la actividad peroxidasa y la concentración de proteínas en la expresión del sistema de defensa de Phaseolus vulgaris L., sometido a diferentes preparaciones homeopáticas. Los tratamientos consistieron en: Arsenicum album, Staphisagria, Silicea y Sulphur, en las potencias 6, 12 y 18 CH, en comparación con los controles. Las semillas se sembraron en macetas mantenidas en invernadero. Los tratamientos se aplicaron al 1% en agua destilada de la siembra, con intervalos de 15 días hasta la etapa R7. La primera evaluación se realizó a los 15 y 60 días después de la siembra, luego de un daño mecánico artificial. Se determinó la concentración de proteínas, la actividad de las enzimas guayacol peroxidasa (POD) y ascorbato peroxidasa (APX). Las diferencias entre tratamientos y controles se estimaron analizando el tamaño del efecto Glass Delta. Staphisagria 12CH indujo un mayor aumento en la concentración de proteínas en las hojas de frijol. Se observaron actividades de inducción de APX y POD en hojas tratadas con azufre en todas las potencias probadas. El efecto Glass Delta mostró un comportamiento oscilatorio en todas las evaluaciones. Las preparaciones homeopáticas tienen el potencial de inducir mecanismos de defensa bioquímicos en Phaseolus vulgaris L., actuando como inductores de resistencia. O objetivo deste trabalho foi avaliar a atividade da peroxidase e a concentração de proteínas na expressão do sistema de defesa de Phaseolus vulgaris L., submetido a diferentes preparações homeopáticas. Os tratamentos foram compostos por: Arsenicum album, Staphisagria, Silicea e Sulphur, nas potências 6, 12 e 18 CH, comparados aos controles. As sementes foram semeadas em vasos mantidos em casa de vegetação. Os tratamentos foram aplicados a 1% em água destilada a partir da semeadura, com intervalos de 15 dias até o estádio R7. A primeira avaliação foi realizada 15 e 60 dias após a semeadura, após danos mecânicos artificiais. A concentração de proteínas, atividade das enzimas guaiacol peroxidase (POD) e ascorbato peroxidase (APX) foram determinadas. As diferenças entre os tratamentos e os controles foram estimadas pela análise do tamanho do efeito Glass Delta. Staphisagria 12CH induziu maior aumento na concentração de proteína nas folhas do feijoeiro. As atividades de indução de APX e POD foram observadas em folhas tratadas com Sulphur em todas as potências testadas. O efeito Glass Delta apresentou comportamento oscilatório, em todas as avaliações. As preparações homeopáticas têm potencial para induzir mecanismos de defesa bioquímica em Phaseolus vulgaris L., atuando como eliciadores de resistência.

Cold-tolerance in rice may be related to increased cellulose deposition in the cell wall, membrane fatty acids unsaturation and differential expression of several newly identified genes. Low temperature exposure during early vegetative stages limits rice plant’s growth and development. Most genes previously related to cold tolerance in rice are from the japonica subspecies. To help clarify the mechanisms that regulate cold tolerance in young indica rice plants, comparative transcriptome analysis of 6 h cold-treated (10 °C) leaves from two genotypes, cold-tolerant (CT) and cold-sensitive (CS), was performed. Differentially expressed genes were identified: 831 and 357 sequences more expressed in the tolerant and in the sensitive genotype, respectively. The genes with higher expression in the CT genotype were used in systems biology analyses to identify protein–protein interaction (PPI) networks and nodes (proteins) that are hubs and bottlenecks in the PPI. From the genes more expressed in the tolerant plants, 60% were reported as affected by cold in previous transcriptome experiments and 27% are located within QTLs related to cold tolerance during the vegetative stage. Novel cold-responsive genes were identified. Quantitative RT-PCR confirmed the high-quality of RNAseq libraries. Several genes related to cell wall assembly or reinforcement are cold-induced or constitutively highly expressed in the tolerant genotype. Cold-tolerant plants have increased cellulose deposition under cold. Genes related to lipid metabolism are more expressed in the tolerant genotype, which has higher membrane fatty acids unsaturation, with increasing levels of linoleic acid under cold. The CT genotype seems to have higher photosynthetic efficiency and antioxidant capacity, as well as more effective ethylene, Ca2+ and hormone signaling than the CS. These genes could be useful in future biotechnological approaches aiming to increase cold tolerance in rice.

Exposure to low temperature during germination and vegetative growth is a limiting factor to the establishment and development of rice seedlings. Higher cold tolerance of japonica than indica subspecies is well documented. However, reports of cold tolerance in indica genotypes are rare. We screened a large number of indica rice genotypes for cold tolerance during germination and initial vegetative growth. The indica genotypes IRGA 959-1-2-2F-4-1-4-A and IRGA 959-1-2-2F-4-1-4-D-1-CA-1, derived from the same cross, were characterized, respectively, as tolerant and sensitive to low temperature. Indexes of photosynthetic performance during light absorption were heavily affected by cold in both genotypes, but recovered after cold exposure only in the tolerant genotype. Activities of the antioxidant enzymes SOD and CAT (at the vegetative stage) and CAT and APX (at the germination stage) were higher in the tolerant than in the sensitive genotype. Expression of 20 genes previously related to cold response in rice was evaluated. Expression of OsLIP9 and OsWCOR413 were higher in the tolerant genotype upon or prior to cold exposure, respectively. The two sister lines show different molecular and physiological responses to low temperature stress. Further in-depth studies with these lines may help to identify new cold tolerance mechanisms in rice.

The objective of this work was to evaluate the effect on the physiological and biochemical aspects of garlic submitted to water deficit, knowing that the popular garlic Allium sativum L. is a culture known worldwide for its medicinal, culinary and ecological properties of agricultural pests. were constituted with water condition of 100; 75; 50 and 25% of pot capacity (CP). Three bulbs were planted per pot (5 L) containing Plantmax® substrate, irrigated every two days, according to pot capacity. The chlorophyll index was evaluated during the first and last week of greenhouse treatments. At 45 days after the treatments, the garlic plants were harvested to evaluate the physiological and biochemical parameters. Garlic plants showed to be sensitive to water deficit, resulting in lower leaf length and fresh biomass. Water stress induced the activity of the APX enzyme in the leaves and of the POD in the roots, as well as increase of proteins in the bulbilhos as biochemical mechanisms of adaptation.

The mineral nutritional homeostasis in response to different concentrations of Hg (0, 25 and 50μM) was evaluated in Pfaffia glomerata plant. The exposure to the highest level of Hg (50µM) caused a decreasing in shoot and root fresh weights of 15.5% and 20%, respectively. Both shoot and root Hg concentrations increased linearly with increasing external Hg concentrations. Ca concentration decreased in shoot only at 50µM Hg, whereas shoot K and Mg concentrations decreased at both 25 and 50µM Hg, when compared to the control. A significant decrease in Cu, Zn, Fe and Mn concentrations in plants exposed to Hg was observed, but most Zn, Mn, and Cu in the roots. On the other hand, P concentration increased in both root and shoot of plants exposed at 25 and 50µM Hg, whereas Na concentration increased only in the root at 25 and 50µM Hg exposure. In general, tissue nutrient concentrations in P. glomerata plantlets exposed to Hg were significantly decreased, which indicates that the Hg may cause alteration on the mineral nutritional homeostasis of this species. RESUMO: A homeostase nutricional mineral em resposta a diferentes concentrações de Hg (0, 25 e 50μM) foram avaliadas em plantas de Pfaffia glomerata. A exposição ao mais alto nível de Hg (50µM) causou um decréscimo de 15,5% e 20%, respectivamente, na matéria fresca da parte aérea e raízes. As concentrações de Hg na parte aérea e raízes aumentaram linearmente com o aumento das concentrações de Hg. A concentração de Ca decresceu na parte aérea somente em 50µM Hg, enquanto as concentrações de K e Mg na parte aérea decresceram tanto em 25 como em 50µM Hg, quando comparado ao controle. Observou-se um significativo decréscimo nas concentrações de Cu, Zn, Fe e Mn nas plantas expostas ao Hg, mas principalmente Zn, Mn e Cu nas raízes. Por outro lado, a concentração de P aumentou em raízes e parte aérea de plantas expostas a 25 e 50µM Hg, enquanto a concentração de Na aumentou somente nas raízes em 25 e 50µM Hg. No geral, as concentrações de nutrientes nos tecidos de P. glomerata expostas ao Hg foram significativamente diminuídas, o que indica que o Hg pode causar alterações na homeostase nutricional mineral dessa espécie.

Rice productivity is largely affected by low temperature, which can be harmful throughout plant development, from germination to grain filling. Germination of indica rice cultivars under cold is slow and not uniform, resulting in irregular emergence and small plant population. To identify and characterize novel genes involved in cold tolerance during the germination stage, two indica rice genotypes (sister lines previously identified as cold-tolerant and cold-sensitive) were used in parallel transcriptomic analysis (RNAseq) under cold treatment (seeds germinating at 13 °C for 7 days). We detected 1,361 differentially expressed transcripts. Differences in gene expression found by RNAseq were confirmed for 11 selected genes using RT-qPCR. Biological processes enhanced in the cold-tolerant seedlings include: cell division and expansion (confirmed by anatomical sections of germinating seeds), cell wall integrity and extensibility, water uptake and membrane transport capacity, sucrose synthesis, generation of simple sugars, unsaturation of membrane fatty acids, wax biosynthesis, antioxidant capacity (confirmed by histochemical staining of H2O2), and hormone and Ca(2+)-signaling. The cold-sensitive seedlings respond to low temperature stress increasing synthesis of HSPs and dehydrins, along with enhanced ubiquitin/proteasome protein degradation pathway and polyamine biosynthesis. Our findings can be useful in future biotechnological approaches aiming to cold tolerance in indica rice.

Aluminum (Al) toxicity is a limiting factor for crop production in acid soils, which cover approximately 60% of the Brazilian territory. This study aimed to evaluate the effects of Al on growth and tissue Al concentration of two Pfaffia glomerata accessions (BRA and JB/UFSM). Plantlets were grown in a hydroponic system with five Al concentrations (0, 50, 100, 150 and 200mg L-1) for 7 days. Most of the evaluated parameters presented significant interaction between both P. glomerata accessions and Al levels in nutrient solution and, in general, Al treatments negatively affected plant growth, especially roots. Moreover, BRA accession showed higher Al accumulation in its tissues than JB/UFSM and, consequently in BRA accession the growth was impaired substantially. Furthermore, the results suggest that, between P. glomerata accessions studied, BRA is less appropriated for medicinal uses when grown in soils with high Al levels, due to the higher accumulation of tissue Al content.

Rice is a staple food for half of the human population. Unlike other cereals such as wheat and barley, rice plants are susceptible to cold stress, which often results in decreased productivity, especially in regions where the indica subspecies is cultivated. Low temperatures can have negative impacts on rice plants during germination, vegetative growth, and reproductive stages. Considering the expected higher frequency of extreme temperature events in the near future, cold waves could even increase the negative impacts of low temperatures in rice production. Here, we review the efforts that have been made to achieve cold tolerance in rice through breeding, the major tools used for evaluating cold tolerance in rice plants, the discovery of quantitative trait loci (QTLs) and genes related to this tolerance, and the results obtained so far by genetic transformation of rice plants with potential cold-tolerance genes. Although much progress has been achieved, joint efforts from breeders and plant biologists could speed up the production of cold-tolerant rice plants, and some possible approaches are suggested.

The aim of this study was to assess the effect of aluminum on the in vitro activity of acid phosphatases (APases) of four potato clones, Macaca and Dakota Rose (Al-sensitive), and SMIC148-A and Solanum microdontum (Al-tolerant), grown in vitro, in hydroponics or in a greenhouse. The enzyme was assayed in vitro in the presence of 0, 1.85, 3.70, 5.55 and 7.40 mM Al. In plantlets grown in vitro, root APases were inhibited by Al in all clones, while shoot APases were inhibited by Al in S. microdontum and Dakota Rose and increased in Macaca at all Al concentrations. In plantlets grown in hydroponics, root APases increased in Macaca at 1.85 mM Al, whereas decreased at all Al levels in S. microdontum. In greenhouse plantlets, root APases decreased at 7.40 mM Al in S. microdontum and SMIC148-A, and at 3.70, 5.55 and 7.40 mM Al in Dakota Rose. Shoot APases decreased in Macaca and SMIC148-A. Conversely, in Dakota Rose, APases increased at 1.85 and 3.70 mM Al. These results show that the effect of Al toxicity on in vitro APase activity depends not only on Al availability but also on the plant organ, genetic background, and the growth conditions. Therefore, it suggests that acid phosphatases activity assessed in vitro might not be a good parameter to validate the screening for adaptation of potato clones to Al toxicity.

The phytotoxic effects of aluminum and the mechanisms of genetically-based Al tolerance have been widely investigated, as reported in many papers and reviews. However, investigations on many Al-sensitive and Al-resistant species demonstrate that Al phytotoxicity and Al-resistance mechanisms are extremely complex phenomena. The objective of the present study was to analyze the effects of aluminum on the activity of antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX). Also was evaluated the lipid peroxidation, H(2)O(2) content, levels of ascorbic acid (ASA), non-protein thiols (NPSH) and Al content in three genotypes of oat, Avena sativa L. (UFRGS 930598, UFRGS 17, and UFRGS 280). The genotypes were grown in different concentrations of Al ranging from 90 to 555 μM for 5 days. The antioxidant system was unable to overcome toxicity resulting in negative effects such as lipid peroxidation and H(2)O(2) content in UFRGS 930598. The results showed that UFRGS 930598 was the most sensitive genotype. UFRGS 17 and UFRGS 280 were more resistant to Al toxicity. These results suggest that UFRGS 17 has mechanisms of external detoxification and UFRGS 280 has mechanisms of internal detoxification. The different behavior of enzymatic and non-enzymatic antioxidants of the genotypes showed that aluminum resistance in UFGRS 17 and UFRGS 280 may be related to oxidative stress.

Oxidative stress caused by mercury (Hg) was investigated in Pfaffia glomerata plantlets grown in nutrient solution using sand as substrate. Thirty-day-old acclimated plants were treated for 9 days with four Hg levels (0, 1, 25 and 50 microM) in the substrate. Parameters such as growth, tissue Hg concentration, toxicity indicators (delta-aminolevulinic acid dehidratase, delta-ALA-D, activity), oxidative damage markers (TBARS, lipid peroxidation, and H(2)O(2) concentration) and enzymatic (superoxide dismutase, SOD, catalase, CAT, and ascorbate peroxidase, APX) and non-enzymatic (non-protein thiols, NPSH, ascorbic acid, AsA, and proline concentration) antioxidants were investigated. Tissue Hg concentration increased with Hg levels. Root and shoot fresh weight and delta-ALA-D activity were significantly decreased at 50 microM Hg, and chlorophyll and carotenoid concentration were not affected. Shoot H(2)O(2) concentration increased curvilinearly with Hg levels, whereas lipid peroxidation increased at 25 and 50 microM Hg, respectively, in roots and shoots. SOD activity showed a straight correlation with H(2)O(2) concentration, whereas CAT activity increased only in shoots at 1 and 50 microM Hg. Shoot APX activity was either decreased at 1 microM Hg or increased at 50 lM Hg. Conversely, root APX activity was only increased at 1 microM Hg. In general, AsA, NPSH and proline concentrations increased upon addition of Hg, with the exception of proline in roots, which decreased. These changes in enzymatic and non-enzymatic antioxidants had a significant protective effect on P. glomerata plantlets under mild Hg-stressed conditions.

The objective of this study was to evaluate whether the oxidative stress caused by aluminum (Al) toxicity is an early symptom that can trigger root growth inhibition in Macaca (Al-sensitive) and SMIC148-A (Al-tolerant) potato clones. Plantlets were grown in a nutrient solution (pH 4.00) with 0, 100 and 200mg Al L(-1). At 24, 72, 120 and 168h after Al addition, root length and biochemical parameters were determined. Regardless of exposure time, root length of the Macaca clone was significantly lower at 200mg Al L(-1). For the SMIC148-A clone, root length did not decrease with any Al treatments. Al supply caused lipid peroxidation only in Macaca, in both roots (at 24, 72, 120 and 168h) and shoot (at 120 and 168h). In roots of the Macaca, catalase (CAT) and ascorbate peroxidase (APX) activity decreased at 72 and 120h, and at 24, 72 and 120h, respectively. At 168h, both activities increased upon addition of Al. In roots of the SMIC148-A, CAT activity increased at 72 and 168h, whereas APX activity decreased at 72h and increased at 24, 12 and 168h. The Macaca showed lower root non-protein thiol group (NPSH) concentration at 200mg Al L(-1) in all evaluations, but the SMIC148-A either did not demonstrate any alterations at 24 and 72h or presented higher levels at 120h. This pattern was also observed in root ascorbic acid (AsA) concentration at 24 and 120h. The cellular redox status of these potato clones seems to be affected by Al. Therefore, oxidative stress may be an important mechanism for Al toxicity, mainly in the Al-sensitive Macaca clone.

A hydroponic experiment was carried out to characterize the oxidative stress responses of two potato cultivars (Solanum tuberosum L. cvs. Asterix and Macaca) to cadmium (Cd). Plantlets were exposed to four Cd levels (0, 50, 100, 150 and 200 microM) for 7 days. Cd concentration was increased in both roots and shoot. Number of sprouts and roots was not decreased, whereas Cd treatment affected the number of nodal segments. Chlorophyll content and ALA-D activity were decreased in both cultivars, whereas carotenoids content was decreased only in Macaca. Cd caused lipid peroxidation in roots and shoot of both cultivars. Protein oxidation was only verified at the highest Cd level. H(2)O(2) content was increased in roots and shoot of Asterix, and apparently, a compensatory response between roots and shoot of Macaca was observed. SOD activity was inhibited in roots of Asterix at all Cd treatments, whereas in Macaca it was only increased at two highest Cd levels. Shoot SOD activity increased in Asterix and decreased in Macaca. Root CAT activity in Asterix decreased at 100 and 150 microM, whereas in Macaca it decreased only at 50 microM. Shoot CAT activity was decreased in Macaca. Root AsA content in Macaca was not affected, whereas in shoot it was reduced at 100 microM and increased at 200 microM. Cd caused increase in NPSH content in roots and shoot. Our results suggest that Cd induces oxidative stress in both potato cultivars and that of the two cultivars, Asterix showed greater sensitivity to Cd levels.

In this study, the effects of cadmium chloride (CdCl2) on plant growth, histology of roots, photosynthetic pigments content, δ-aminolevulinic acid dehydratase (ALA-D; E.C. 4.2.1.24) and acid phosphatase activities (AP; E.C. 3.1.3.2), soluble phosphorus (Pi) measurement and mineral nutrients content in cucumber seedlings (Cucumis sativus L.) were investigated. Cucumber seedlings were grown in vitro in an agar-solidified substrate containing four CdCl2 treatments (0, 100, 400, and 1000 μM) for ten days. Cd was readily absorbed by seedlings and its content was greater in the roots than in the shoot. Cd reduced shoot and root length, and fresh and dry biomass of seedlings. Inhibition of root cell elongation in Cd-treated seedlings was observed by the increase of the mean radial size of cells belonging to three zones of the root tip. The highest level of Cd reduced in a similar manner chlorophyll a, chlorophyll b and total chlorophyll contents. Increasing concentrations of Cd resulted in a linear decrease in carotenoids levels of cotyledons. Interestingly, the ALA-D activity in cotyledons was inhibited only at the highest level of Cd. Root and shoot AP activities were, respectively, activated and inhibited at all CdCl2 concentrations. Root Pi concentration was increased in all Cd treatments and it was not altered in the shoot tissues. Moreover, in general, the nutrient contents were increased in the root and decreased in the shoot. Therefore, we suggest that Cd affects negatively growth, photosynthetic pigments, ALA-D and AP activities and partition of mineral nutrients in cucumber seedlings.

In this study, the effects of lead (Pb) on growth, photosynthetic pigments concentration, lipid peroxidation, electrolyte leakage percentage (ELP), protein oxidation, aminolevulinate dehydratase (ALA-D; E.C. 4.2.1.24), ascorbate peroxidase (APX; E.C. 1.11.1.11), catalase (CAT; E.C. 1.11.1.6) and superoxide dismutase (SOD; E.C. 1.15.1.1) activities, and ascorbic acid (AsA), non-protein thiol groups (NPSH) and total soluble protein concentrations in cucumber seedlings (Cucumis sativus L.) were investigated. Seedlings were grown in vitro in an agar-solidified substrate containing three Pb levels as (C2H3O2)Pb.3H2O (0, 100, 400, and 1000 µmol L-1) for 10 d. Increasing Pb concentrations in substrate enhanced Pb concentration in both roots and shoot. Pb accumulated at a higher amount in roots. Root length and total fresh weight were decreased at the two highest Pb concentrations. Cucumber showed no reduction in shoot length and total dry weight at any Pb level. The highest Pb concentration decreased water content and ALA-D activity as well as increased malondialdehyde, carbonyls and total soluble protein concentrations. Carotenoids concentration enhanced at 100 and 400 µmol Pb L-1, while chlorophyll concentration and ELP were not affected by Pb stress. Activity of APX was inhibited while the activities of CAT and SOD were increased at all Pb concentrations. AsA was enhanced at 400 and 1000 µmol Pb L-1 whereas NPSH were increased only at the highest Pb concentration. Therefore, high Pb-exposure caused oxidative stress, and the antioxidant system of the cucumber seedlings was not sufficient to revert it, contributing for growth reduction.

Pfaffia glomerata (Spreng.) Pedersen plantlets were grown under different cadmium (Cd) concentrations (0, 20, 40, 60 and 80 μM) in a hydroponic system during 7 d. Plant growth, micronutrient, chlorophyll and carotenoid concentrations, as well as δ-aminolevulinic acid dehydratase (ALA-D; E.C.4.2.1.24) and acid phosphatase (AP; E.C.3.1.3.2) activities were then analysed. Cadmium concentration in both shoots and roots increased with increasing external Cd levels. Metal concentration was on average 12-fold greater in root than in shoot tissues. Root length was unaffected by Cd treatments. In contrast, dry weight of both shoot and roots increased significantly upon addition of 20 and 40 μM Cd. Moreover, shoot and total plant dry weight was only reduced in plants treated with 80 μM Cd. Conversely, root dry weight decreased significantly upon addition of Cd concentrations above 40 μM. A micronutrient- and organ-dependent response to Cd toxicity was observed. Zinc and Cu concentrations in both shoot and roots did not alter upon treatment with Cd. Cadmium stress reduced Mn uptake but not its translocation within the plant. A synergistic effect of Cd on Fe concentration in root at 20 μM and 80 μM Cd levels was observed. The activity of AP, and especially that of ALA-D, was reduced with increasing Cd levels. At those these Cd levels, chlorophyll concentration was also reduced. There was a positive correlation between concentrations of carotenoids and chlorophylls. Our results indicate that P. glomerata seems to have some degree of Cd tolerance. Plântulas de Pfaffia glomerata (Spreng.) Pedersen foram cultivadas em cinco níveis (0, 20, 40, 60 e 80 μM) de cádmio (Cd) em um sistema hidropônico durante 7 d, visando-se analisar o crescimento, as concentrações de micronutrientes, clorofilas e carotenóides, bem como as atividades da desidratase do ácido δ-aminolevulínico (ALA-D; E.C.4.2.1.24) e fosfatase ácida (AP; E.C.3.1.3.2) nas plantas. A concentração de Cd, na parte aérea e raízes, aumentou com o incremento dos níveis de Cd. A concentração de Cd nas raízes foi, em média, 12 vezes maior do que na parte aérea. O comprimento das raízes não foi afetado pelos tratamentos de Cd. Em contraste, a biomassa seca da parte aérea e raízes aumentou significativamente pela adição de 20 e 40 μM Cd. Além disso, a biomassa seca total das plantas somente diminuiu no nível de 80 μM Cd em relação à das plantas-controle. Por outro lado, a biomassa radicular diminuiu significativamente pela adição de Cd a níveis superiores a 40 μM. Constatou-se resposta dependente do órgão e do micronutriente à toxicidade de Cd. As concentrações de Zn e Cu na parte aérea e raízes não foram alteradas pela presença de Cd. A absorção de Mn foi diminuída pelo estresse de Cd, porém sua translocação não foi alterada. Um efeito sinergístico do Cd na concentração de Fe nas raízes foi observado nos níveis de 20 e 80 μM Cd. As atividades da ALA-D e AP foram diminuídas com o incremento dos níveis de Cd, porém a ALA-D foi mais afetada. Naquelas concentrações de Cd, a concentração de clorofila também foi diminuída. Houve uma correlação positiva entre as concentrações de carotenóides e clorofila. Os resultados indicam que a P. glomerata parece ter algum grau de tolerância ao Cd.

Acid phosphatases (3.1.3.2) are a group of enzymes widely distributed in nature, which catalyze the hydrolysis of a variety of phosphate esters in the pH range of 4-6. We confirmed the presence of acid phosphatases in seedlings of cucumber (Cucumis sativus), radish (Raphanus sativus) and rocket salad (Eruca vesicaria) under different assay conditions using a rapid and simple preparation. The results showed that the optimum pH and temperature used for all species were close to 5.5 and 35°C, respectively. The enzyme was inhibited by molybdate, fluoride, azide, levamisole, orthovanadate, Zn2+ and Cu2+. Suramin had no effect on enzyme activity. The acid phosphatase from cucumber, radish and rocket salad hydrolyzed a wide variety of phosphate esters and the highest activity was observed with PPi, ATP and GTP. These results demonstrate that the enzyme investigated in this study is different from well known ester phosphate cleaving plant enzymes (apyrase and inorganic pyrophosphatases) and this preparation could be a useful tool to future toxicological studies and to study initially all isoforms of acid phosphatase. As fosfatases ácidas (3.1.3.2) são um grupo de enzimas amplamente distribuídas na natureza, as quais catalisam a hidrólise de uma variedade de ésteres de fosfato com uma variação de pH entre quatro e seis. Foi confirmada a presença de fosfatases ácidas em plântulas de pepino (Cucumis sativus), rabanete (Raphanus sativus) e rúcula (Eruca vesicaria) sob diferentes condições de ensaio usando uma preparação rápida e simples. Os resultados mostraram que o pH e a temperatura ótimos para todas as espécies foram 5,5 e 35°C, respectivamente. A enzima foi inibida por molibdato, fluoreto, azida, levamisole, ortovanadato, Zn2+ e Cu2+. O inibidor suramim não afetou a atividade enzimática. As fosfatases ácidas de pepino, rabanete e rúcula hidrolisaram uma ampla variedade de ésteres de fosfato e a maior atividade foi observada com PPi, ATP e GTP para pepino e rabanete e PPi, frutose-6-fosfato e GTP para rúcula. Esses resultados demonstraram que a enzima investigada neste estudo é diferente das conhecidas enzimas de plantas que clivam ésteres de fosfato (apirase e pirofosfatases inorgânicas). Desse modo, esta preparação pode ser uma ferramenta útil para futuros estudos toxicológicos e para se estudar inicialmente todas as isoformas das fosfatases ácidas.

In this study, the effects of cadmium (Cd) on lipid peroxidation, electrolyte leakage, protein oxidation, ascorbate peroxidase (APX; E.C. 1.11.1.11), catalase (CAT; E.C. 1.11.1.6) and superoxide dismutase (SOD; E.C. 1.15.1.1) activities, and ascorbic acid, non-protein thiol groups and total soluble protein contents in cucumber seedlings (Cucumis sativus L.) were investigated. Seedlings were grown in vitro in an agar-solidified substrate containing four Cd levels as CdCl2 (0, 100, 400, and 1000 µmol L-1) for 10 d. The lowest Cd level decreased the malondialdehyde concentration. Electrolyte leakage increased only at 1000 µmol Cd L-1, whereas protein oxidation and total soluble protein content were enhanced at 400 and 1000 µmol Cd L-1. Activity of APX was inhibited while the activities of CAT and SOD were increased at all Cd concentrations. Ascorbic acid was enhanced at 400 and 1000 µmol Cd L-1 whereas non-protein thiol groups were increased at all Cd supplies. The results evidence the importance of the enzymatic and non-enzymatic antioxidant system in response to cadmium toxicity in cucumber seedlings.

Aluminum toxicity is a serious problem in Brazilian soils and selecting potato clones is an important strategy to produce this crop on these kinds of soils. Potato clones, Macaca, SMIC148-A, Dakota Rose, and Solanum microdontum, were grown in a nutrient solution (pH 4.0) with 0, 50, 100, 150 and 200 mg Al L-1. After 7 d, Al concentration in both root system and shoot of all clones increased linearly with increasing Al levels. Based on relative root growth, S. microdontum and SMIC148-A were considered Al-tolerant clones, whereas Macaca and Dakota Rose were considered Al-sensitive. Shoot growth in Macaca linearly decreased with increasing Al levels. Root H2O2 concentration in both Al-sensitive clones increased with increasing Al supply, whereas in Al-tolerant clones it either decreased (SMIC148-A) or demonstrated no alteration (S. microdontum). Shoot H2O2 concentration increased linearly in Macaca, whereas for Dakota Rose it showed a quadratic relationship with Al levels. On the other hand, shoot H2O2 concentration in the Al-tolerant clones either demonstrated no alteration (S. microdontum) or presented lower levels (SMIC148-A). Root catalase (CAT) activity in both Al-sensitive clones increased with increasing Al levels, whereas in Al-tolerant clones it either demonstrated no alteration (SMIC148-A) or presented lower levels (S. microdontum). Shoot CAT activity in the S. microdontum increased curvilinearly with increasing Al levels. In all potato clones, chlorophyll concentration showed a curvilinear response to Al supply, where in Al-sensitive clones it decreased upon addition of Al exceeding 100 mg L-1, but in SMIC148-A it increased at levels between approximately 100 and 150 mg L-1, and decreased in S. microdontum regardless of the Al level. Carotenoid concentrations in the Al-sensitive clones were linearly decreased with increasing Al levels. Aluminum supply caused root lipid peroxidation only in the Al-sensitive clones, whereas in the shoot it increased linearly in the Al-sensitive clones and in S. microdontum it only increased at around 50 mg L-1. Most of root protein oxidation was only observed in the Al-sensitive clones. However, shoot protein oxidation was increased with increasing Al levels for all potato clones. These results indicate that oxidative stress caused by Al in potato may harm several components of the cell, mainly in Al-sensitive clones. Atoxicidade do alumínio é um problema sério em solos brasileiros e a seleção de clones de batata é uma estratégia importante para produzir essa cultura em tais solos. Clones de batata, Macaca, SMIC148-A, Dakota Rose e Solanum microdontum, foram cultivados em solução nutritiva (pH 4.0) com 0, 50, 100, 150 e 200 mg Al L-1. Após 7 d, o teor de Al em raízes e parte aérea em todos clones aumentou linearmente com o suprimento de Al. Baseado no crescimento relativo da raiz, os clones S. microdontum e SMIC148-A foram considerados tolerantes ao Al, enquanto os clones Macaca e Dakota Rose foram considerados sensíveis. O crescimento da parte aérea do clone Macaca diminuiu linearmente com o Al. A concentração de H2O2 nas raízes de ambos os clones sensíveis ao Al aumentou com o suprimento de Al, enquanto nos clones tolerantes houve decréscimo (SMIC148-A) ou falta de resposta (S. microdontum). A concentração de H2O2 na parte aérea aumentou linearmente em Macaca, enquanto em Dakota Rose houve uma relação quadrática com os níveis de Al. Por outro lado, nos clones tolerantes ao Al a concentração de H2O2 não foi alterada (S. microdontum) ou foi reduzida (SMIC148-A). A atividade da catalase (CAT) nas raízes de ambos clones sensíveis ao Al aumentou com o suprimento de Al, enquanto nos clones tolerantes não houve alteração (SMIC148-A) ou, então, redução (S. microdontum). Na parte aérea, a atividade da CAT em S. microdontum aumentou com o suprimento de Al. Em todos clones de batata, a concentração de clorofila variou curvilinearmente em relação ao suprimento de Al; nos clones sensíveis, a concentração de clorofila diminuiu pela adição de Al em níveis acima de 100 mg L-1, porém em SMIC148-A houve aumento na presença de Al (na faixa próxima a 100 e 150 mg L-1) e diminuição em S. microdontum, independentemente do tratamento de Al. A concentração de carotenóides nos clones sensíveis ao Al diminuiu linearmente, em resposta ao Al. O Al aumentou a peroxidação lipídica em raízes dos clones sensíveis, enquanto na parte aérea houve aumento linear nesses clones e também em S. microdontum (próximo a 50 mg Al L-1). A oxidação protéica foi observada principalmente nas raízes dos clones sensíveis ao alumínio. Entretanto, foi observada oxidação protéica na parte aérea de todos clones de batata, em resposta ao Al. Estes resultados indicam que o estresse oxidativo causado por Al em batata pode prejudicar vários componentes celulares, principalmente nos clones sensíveis ao metal.

Acid phosphatases (E.C.3.1.3.2) are a group of enzymes widely distributed in nature, which nonspecifically catalyze the hydrolysis of a variety of phosphate esters in pH ranges from 4 to 6 and play a major role in the supply and metabolism of phosphate in plants. The objective of the present study was to investigate the in vitro effects of some metals on the activity of acid phosphatase in cucumber seedlings ( Cucumis sativus L.) and to determine their kinetic parameters. The enzyme was assayed with Hg, Cd, Mn, Pb, Zn, K and Na at the 0.001–1 mM range using ATP, PPi and β-glycerol phosphate as substrates. Mn, Na and Cd did not significantly alter the enzyme activity. K caused a broad activation at low concentrations and an inhibition at high concentrations (10 mM) and lead caused no inhibition. Acid phosphatase was inhibited by Hg and Zn and the inhibition type and IC 50 values were determined for these metals. Hg presented a mixed inhibition type with PPi and ATP as substrates and uncompetitive inhibition with β-glycerol phosphate as substrate. Zn presented competitive inhibition for ATP as substrate, and a mixed inhibition type with PPi and β-glycerol phosphate as substrate. IC 50 values were 0.02, 0.3 and 0.15 mM for Hg, and 0.056, 0.035 and 0.24 mM for Zn with ATP, PPi and β-glycerol phosphate as substrates, respectively. Analysis of these results indicates that Zn is a more potent inhibitor of acid phosphatase from cucumbers than Hg.

In this study, the effects of exogenous mercury (HgCl(2)) on time-dependent changes in the activities of antioxidant enzymes (catalase and ascorbate peroxidase), lipid peroxidation, chlorophyll content and protein oxidation in cucumber seedlings (Cucumis sativus L.) were investigated. Cucumber seedlings were exposed to from 0 to 500microM of HgCl(2) during 10 and 15 days. Hg was readily absorbed by growing seedlings, and its content was greater in the roots than the in shoot. Time and concentration-dependent reduction in root and shoot length was observed at all concentrations tested, equally in the roots and shoot, at both 10 and 15 days. At 50microM HgCl(2), root fresh weight of 15-day-old seedlings increased, and at other concentrations, it reduced. For 10-day-old seedlings, reduction in root and shoot fresh biomass was observed. At 15 days, only at 50microM HgCl(2) was there no observed reduction in shoot fresh biomass. Dry weight of roots increased at 500microM both at 10 and 15 days, though at 250microM HgCl(2) there was only an increase at 15 days. There was a significant effect on shoot dry weight at all concentrations tested. Hg-treated seedlings showed elevated levels of lipid peroxides with a concomitant increase in protein oxidation levels, and decreased chlorophyll content when exposed to between 250 and 500microM of HgCl(2). At 10 days, catalase activity increased in seedlings at a moderately toxic level of Hg, whereas at the higher concentration (500microM), there was a marked inhibition. Taken together, our results suggest that Hg induces oxidative stress in cucumber, resulting in plant injury.

Apyrase and 5'-nucleotidase activities were analyzed in an ethidium bromide (EB) demyelinating model associated with interferon-beta (IFN-beta). The animals were divided in groups: I, control (saline); II, saline and IFN-beta; III, EB and IV, EB and IFN-beta. After 7, 15 and 30 days the animals (n = 5) were sacrificed and the cerebral cortex was removed for synaptosome preparation and enzymatic assays. Apyrase activity using ATP as substrate increased in groups II, III and IV (P0.001) after 7 days and in groups III and IV (P0.001) after 15 days. Using ADP as substrate, an activation of this enzyme was observed in group III (P0.05) after seven and 15 days. The 5'-nucleotidase activity increased in group III (P0.05) after 7 days and in groups II, III and IV (P0.001) after 15 days. After 30 days treatment, no significant alteration was observed in enzyme activities. Results showed that apyrase and 5'-nucleotidase activities are altered in demyelination events and that IFN-beta was able to regulate the adenine nucleotide hydrolysis.

The objective of this study was to evaluate whether the oxidative stress caused by aluminum (Al) toxicity is a symptom that can trigger root growth inhibition in oat genotype seedlings. Oat seedlings were grown in a nutrient solution (pH 4.0) with 0 and 370 μM Al. At 12, 24, and 36 h after Al addition, growth (root length) and biochemical parameters (catalase — CAT, ascorbate peroxidase — APX, and superoxide dismutase — SOD activities, lipid peroxidation, ascorbic acid (ASA) and non-protein thiol group (NPSH) concentration) were determined. The aluminum content was measured in oat seedlings. Regardless of the exposure time, root of the tolerant genotype grew normally with any Al treatments. Al supply caused lipid peroxidation only in the Al-sensitive genotype in roots and shoots (at 12, 24, and 36 h). In sensitive genotype seedlings, CAT, APX, and SOD were activated only at 24 or 36 h. In tolerant and intermediate genotypes, CAT, APX, and SOD were activated at 12, 24, and 36 h. Data for root growth and lipid peroxidation suggested that lipid peroxidation in the sensitive genotype may be an effect of Al toxicity on root growth. Therefore, the tolerant, intermediate, and sensitive genotypes differ in the expression of the amount, type of antioxidants, and speed of activation of antioxidant system, suggesting a varying capacity of these genotypes to deal with oxidative stress, which resulted in varying sensitivity and tolerance to Al.

The possible role of zinc (Zn) to reverse the oxidative stress caused by mercury (Hg) was investigated in Pfaffia glomerata plantlets. Thirty-day-old acclimatized plantlets of P. glomerata were exposed to four treatments: control, 50 μM Zn, 50 μM Hg and 50 μM Zn + 50 μM Hg for 9 days. In Zn + Hg treatment, shoot and root Hg concentrations were 59 and 24% smaller than that plants exposed to 50 μM Hg added alone. An increase in the Zn concentration in the shoot of plants exposed to Zn + Hg occurred, although in the roots Zn concentration was not altered, when compared to the control. Fresh and dry weights, as well as the activity of δ-aminolevulinic acid dehydratase (δ-ALA-D) in Hg-treated plants were significantly reduced. Percentage survival, fresh and dry weights and δ-ALA-D activity of plants treated by 50 μM Zn + 50 μM Hg were greater than of that treated by Hg alone. Moreover, Zn treatment reduced the lipid peroxidation caused by Hg, being this effect related to increased root superoxide dismutase activity, and shoot catalase and ascorbate peroxidase activities. In conclusion, the presence of Zn in the substrate caused a significant reduction in the oxidative stress induced by Hg.

Aluminum (Al) is one of the most abundant elements of the planet and exposure to this metal can cause oxidative stress and lead to various signs of toxicity in plants. Plants are essential organisms for the environment as well as food for humans and animals. The toxic effect of aluminum is the major cause of decreased crop productivity. Thus, the objective of the present study was to analyze the effects of aluminum on the activity of antioxidant enzymes such as catalase (CAT - E.C. 1.11.1.6), superoxide dismutase (SOD - E.C.1.15.1.1) and ascorbate peroxidase (APX - E.C. 1.11.1.11), and on lipid peroxidation, electrolyte leakage percentage (ELP) and chlorophyll and protein oxidation levels in Cucumis sativus L. (cv. Aodai). Seedlings were grown at different concentrations of aluminum ranging from 1 to 2000 microM for 10 days. The increase in ELP and H(2)O(2) production observed in the seedlings may be related to the decreased efficiency of the antioxidant system at higher aluminum concentrations. The antioxidant system was unable to overcome toxicity resulting in negative effects such as lipid peroxidation, protein oxidation and a decrease in the growth of Cucumis seedlings. Aluminum toxicity triggered alterations in the antioxidant and physiological status of growing cucumber seedlings.

The objective of this study was to evaluate the effects of aluminum (Al) on the zinc (Zn), manganese (Mn), iron (Fe) and copper (Cu) concentrations in four potato clones (Macaca and Dakota Rose: both Al-sensitive clones; and SMIC148-A and Solanum microdontum: both Al-tolerant-clones), grown in a nutrient solution (pH 4.00) with 0, 50, 100, 150 and 200mg Al L-1. Root Zn and Fe concentrations decreased linearly with the increase of Al levels in Macaca, SMIC148-A and Dakota Rose and increased linearly in S. microdontum. Shoot Zn concentration showed a quadratic relationship with Al in S. microdontum and SMIC148-A, but a curvilinear response in Dakota Rose. Shoot Fe concentration showed a quadratic relationship with Al in S. microdontum, SMIC148-A and Dakota Rose. Root Mn concentration decreased linearly in Macaca and SMIC148-A, and increased linearly in S. microdontum with Al levels. Mn concentration showed a quadratic relationship with Al in roots of Dakota Rose and in shoot of SMIC148-A, and increased curvilinearly with Al levels in shoot of Dakota Rose. In shoot, there was no alteration in Zn, Fe and Mn in Macaca and Mn concentration in S. microdontum. Roots and shoot Cu concentration increased linearly in Dakota Rose, and showed quadratic relationship with Al in Macaca. Roots Cu concentration showed a quadratic relationship with Al levels in S. microdontum and SMIC148-A. Shoot Cu concentration increased linearly in S. microdontum, and decreased linearly in SMIC148-A. Therefore, the excessive Al accumulation affected the uptake and distribution of Zn, Fe, Mn and Cu in roots and shoot of potato clones.The response of shoot Cu concentration to Al was less altered in the Al-tolerant clones than was in Al-sensitive clones. Aluminum tolerance in S. microdontum may be connected with greater levels of Zn, Fe and Mn in the roots.

Carbofuran and malathion, well known pesticides, and paraquat, a world widely used herbicide, were tested on acetylcholinesterase (AChE) from Bungarus sindanus venom and butyrylcholinesterase (BChE) from human serum. The calculated IC(50 )values for inhibition of venom enzyme by malathion, carbofuran and paraquat were 2.5, 0.14, and 0.16 microM, respectively. The values for inhibition of serum butyrylcholinesterase (BChE) were 3.5, 0.09 and 0.18 microM, respectively. Analysis of kinetic data indicated that the inhibition caused by malathion, carbofuran and paraquat was mixed for venom AChE. For BChE from human serum, the inhibition caused by malathion and paraquat was mixed and for carbofuran it was uncompetitive. The present results suggest a commercial paraquat preparation (a popular herbicide) inhibits cholinesterases with similar or higher potency than classical pesticide inhibitors. Furthermore, this inhibition was observed both in human serum and snake venom, a newly studied source of AChE.

An increased catalase activity in Candida spp. has been suggested as a mechanism that reduces amphotericin B activity. Furthermore, resistance to antifungal agents like amphotericin B has been reported in some cancer patients undergoing chemotherapy treatment. In this study we analysed the influence of chemotherapy agents on catalase activity in Candida albicans, the major species involved in yeast infections. Eight strains of C. albicans isolated from HIV-positive patients were exposed to cyclophosphamide, cytarabine, dacarbazine and methotrexate antineoplastic drugs at the concentrations used during therapy. Catalase activity was measured and compared to the control group. Very significant differences (P0.01) were found when C. albicans was exposed to methotrexate (2 microg ml(-1) = 4 microM). For cyclophosphamide (50 microg ml(-1)), cytarabine (1 microg ml(-1)) and dacarbazine (8 microg ml(-1)), no differences were found (P0.05) between the control and drug-exposed groups. Although more extensive studies are necessary, these data do suggest that the antineoplastic drug methotrexate contributes to the resistance to antifungal drug therapy by varying catalase activity.

Agaricomycetes fungi community at different forest systems in the northwest of Rio Grande do Sul State, Brazil: seasonal deciduous forest and eucalypt monoculture). Monocultures differ from native forests in relation to plant heterogeneity, variety of substrates, and soil humidity, possibly altering the diversity of organisms, such as the fungi. This study aimed to compare the richness, abundance, and composition of Agaricomycetes fungi in a native forest and in a eucalypt monoculture. The fungi were collected in a seasonal deciduous forest area and in a Eucalyptus grandis monoculture, in the northwest of Rio Grande do Sul State, Brazil. The abundance and richness of fungi were significantly lower in the eucalypt plantation than in the native forest and the species composition differed between the areas. Thus, it was concluded that the eucalypt monoculture negatively affects the Agaricomycetes fungi community.