Luisa Louro Martins

Effect of Excess Copper on Tomato Plants: Growth Parameters, Enzyme Activities, Chlorophyll, and Mineral Content

ABSTRACT In this work, the effect of excess copper (Cu) on tomato plants grown in hydroponic solutions for up to 15 days was studied. The solutions contained different Cu concentrations ranging from 0.05, 0.15, 0.20, and 0.35 mM Cu. Dry mass, root length, and foliar area decreased with time and Cu solution concentration. Copper accumulated more heavily in roots than in leaves. Mineral uptake was affected by increasing Cu concentrations in solution with calcium (Ca), iron (Fe), and zinc (Zn) contents in leaves decreasing. Except for Ca, the concentrations of these elements in the roots also decreased, which indicated that root uptake was affected and the translocation to upper plant parts was disrupted. Iron leaf deficiency was the probable cause of the observed chlorosis and decrease in chlorophyll levels. The activities of three enzymes studied in leaves (guaiacol peroxidases (GPOD), catalase (CAT), and polyphenol oxidase (PPO)) increased transiently, probably as an early response mechanism against Cu induced oxidative stress. At higher Cu concentrations, this defense mechanism broke down and the activities of the enzymes decreased accordingly.

Characterization of Plant Antioxidative System in Response to Abiotic Stresses: A Focus on Heavy Metal Toxicity

Reactive Oxygen Species (ROS) are a natural consequence of the aerobic metabolism, and plants have mechanisms to deal with them in normal conditions, controlling the formation and removal rates. Under stress conditions, cell homeostasis is disrupted and ROS production can increase a lot putting a heavy burden on the those antioxidative mechanisms, some of which are activated in order to eliminate the excess ROS (Mittler et al., 2004).

Effect of Heavy Metals in Plants of the Genus Brassica

Several species from the Brassica genus are very important agricultural crops in different parts of the world and are also known to be heavy metal accumulators. There have been a large number of studies regarding the tolerance, uptake and defense mechanism in several of these species, notably Brassica juncea and B. napus, against the stress induced by heavy metals. Numerous studies have also been published about the capacity of these species to be used for phytoremediation purposes but with mixed results. This review will focus on the latest developments in the study of the uptake capacity, oxidative damage and biochemical and physiological tolerance and defense mechanisms to heavy metal toxicity on six economically important species: B. juncea, B. napus, B. oleracea, B. carinata, B. rapa and B. nigra.

Growth and physiological responses to cadmium stress of two populations of Dittrichia viscosa (L.) Greuter

Two clones of Dittrichia viscosa (L.) Greuter from contrasting populations, DV-A (metallicolous) and DV-W (non-metallicolous), were studied to compare Cd accumulation and tolerance. After 10 days of hydroponic culture with 0, 5, 10, and 15 mg Cd L(-1), metal accumulation and plant growth were measured as well as other stress markers such as decrease in the content of photosynthetic pigments, lipid peroxidation, phenols, H(2)O(2), and free proline. We also analyzed the activity of the antioxidant enzymes guaiacol and ascorbate peroxidases, catalase, superoxide dismutase, and glutathione reductase as well as their isoform patterns. Our results confirmed a high Cd tolerance and accumulation in both clones of D. viscosa, which suggests that these traits are constitutive in this species. However, when the Cd concentration in solution exceeded 10 mg Cd L(-1), DV-A was more tolerant than DV-W. The physiological mechanisms involved in Cd tolerance also differed between them, although phenols and guaiacol peroxidase played an important role in both clones. The effective Cd detoxification of DV-A consisted mainly in a promoted ascorbate peroxidase activity and better efficiency of catalase and glutathione reductase enzymes.

Cadmium accumulation and antioxidative defences in Brassica juncea L. Czern, Nicotiana tabacum L. and Solanum nigrum L.

Remediation of sites contaminated with heavy metals using hyperaccumulators seems a promising alternative to engineering approaches. In this work, we compared cadmium (Cd) accumulation and tolerance (based on responses to oxidative stress) in three different species, Brassica juncea (L.) Czern, Nicotiana tabacum L. and Solanum nigrum L., described in the literature as very tolerant or even as hyperaccumulators. The plants were grown in soil spiked with different Cd concentrations (0 – 35 mg kg−1) over a period of 90 days. The translocation factor (TF), used to measure the effectiveness to translocate Cd from roots to shoots, depended greatly on the species. N. tabacum was the plant which exhibited the highest TF values. It was the only plant under study that fulfilled the conditions of a hyperaccumulator for all levels of soil contamination. On the other hand, S. nigrum presented the highest Cd concentration in plant tissues, with TF >1 in the presence of 5 mg Cd kg−1 of soil. Although B. juncea had presented the lowest TF and Cd concentrations, it was the only plant with TF values increasing with the level of cadmium. Oxidative stress in plants was evaluated by lipid peroxidation and activities of catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and superoxide dismutase (SOD), both in roots and shoots. A significant enhancement (versus control) on lipid peroxidation and enzymatic activity of CAT and APX in shoots of B. juncea, N. tabacum and S. nigrum was observed for the highest levels of Cd in soil, 15 and/or 35 mg Cd kg−1. B. juncea presented the most sensitive response of GPX, for all levels of Cd in soil. Lipid peroxidation and CAT activity were greater in shoots than in roots for all plants and soil Cd concentrations. SOD activity did not present consistent trends for any plant.

Influence of bioaccessibility of total mercury, methyl-mercury and selenium on the risk/benefit associated to the consumption of raw and cooked blue shark (Prionace glauca)

This study aimed to identify the benefit and risk associated with raw and cooked blue shark consumption taking into account the bioaccessibility of Se, Hg and MeHg, by using in vitro digestion method. Selenium, Hg and MeHg levels were higher in cooked samples, particularly in grilled blue shark. Whereas Se bioaccessibility was above 83% in grilled samples, Hg and MeHg bioaccessibility was lower in grilled samples with values near 50%. In addition, all Se-Health Beneficial Values were negative and the molar MeHg:Se ratios were higher than one. The risk-benefit assessment yielded a maximum consumption of one yearly meal for raw or cooked blue shark, thus emphasizing the need to recommend the consumption of a wider variety of seafood species in a balanced and healthy diet.

Comparison of cadmium-induced oxidative stress in Brassica juncea in soil and hydroponic cultures

AimsThe objective of this study was to investigate the response of Brassica juncea in the presence of Cd, in hydroponic and soil experiments, and to conclude about common and divergent trends in both cultures.MethodsWe studied the effect of Cd on growth, oxidative damage and antioxidant responses in roots and shoots of B. juncea grown in soil and hydroponic cultures, using typical time-scales for each one. Major ROS-scavenging enzymes such as catalase, ascorbate peroxidase and guaiacol peroxidase were evaluated, as well as lipid peroxidation.ResultsSmall Cd concentrations in the plant led to enhanced plant growth, while large Cd concentrations impaired growth. The increase in lipid peroxidation observed in the presence of Cd was always greater in shoots than in roots. The physiological response to enhanced levels of reactive oxygen species in the presence of Cd included an increase in guaiacol peroxidase, ascorbate peroxidase and catalase activities, but those enzymes were not always enhanced in a similar manner in both cultures.ConclusionsThe main factors responsible for the differences between the experiments in soil and nutrient solution, were the different Cd content in the plant tissues and the different time-scale of the experiments.

Effect of copper on antioxidant enzyme activities and mineral nutrition of white lupin plants grown in nutrient solution

ABSTRACT We analyzed the effect of different copper (Cu) concentrations (0.10, 0.15, 0.20 and 0.35 mM) and time (1 day to 9 days) on several growth and biochemical parameters of roots and shoots of white lupin plants (Lupinus albus cv Estoril) grown in nutrient solution. A significant decrease in leaf fresh weight and leaf area was detected. Copper accumulated in the roots, and an impairment of nutrient translocation was only observed after six days at the highest Cu concentrations applied. A transient increase in the activity of polyphenoloxidase (EC 1.10.3.1) enforces a role for lignification as a defense strategy under enhanced Cu levels. The activities of several antioxidative enzymes were enhanced after Cu application. Our results indicate that Lupinus albus cv ‘Estoril’ is a rather resistant plant that can cope with moderate concentrations of copper, mostly by controlling up to a certain point, the uptake of excessive amounts of this metal.

Improvement in soil and sorghum health following the application of polyacrylate polymers to a Cd-contaminated soil

Contamination of soils with cadmium (Cd) is a serious global issue due to its high mobility and toxicity. We investigated the application of insoluble polyacrylate polymers to improve soil and plant health. Sorghum was grown in a Cd-contaminated sandy soil. Polyacrylate polymers at 0.2% (w/w) were added to half of the soil. Control soil without plants was also included in the experiment. Growth of sorghum was stimulated in the polymer-amended soil. The concentration of Cd in the shoots, and the activities of catalase and ascorbate peroxidase decreased in plants from polymer-amended soil compared with unamended control. The amount of CaCl(2)-extractable Cd in the polymer-amended soil was 55% of that in the unamended soil. The Cd extracted in sorghum shoots was 0.19 mg per plant grown on soil without polymer and 0.41 mg per plant grown on polymer-amended soil. The total amount of Cd removed from each pot corresponded to 1.5 and more than 6% of soil CaCl(2)-extractable Cd in unamended and polymer-amended soil, respectively. The activities of soil acid phosphatase, beta-glucosidase, urease, protease and cellulase were greatest in polymer-amended soil with sorghum. In conclusion, the application of polyacrylate polymers to reduce the bioavailable Cd pool seems a promising method to enhance productivity and health of plants grown on Cd-contaminated soils.

Influence of enzymes and technology on virgin olive oil composition

ABSTRACT This work aims at presenting the state-of-the-art about the influence of the activity of olive endogenous enzymes, as well as of the application of adjuvants in olive oil technology, discussing their influence on the composition of virgin olive oil, especially in phenols and volatile compounds.