Clusia hilariana and Eugenia uniflora as bioindicators of atmospheric pollutants emitted by an iron pelletizing factory in Brazil.

The objectives of this work were to evaluate if the pollution emitted by the pelletizing factory causes visual symptoms and/or anatomical changes in exposed Eugenia uniflora and Clusia hilariana, in active biomonitoring, at different distances from a pelletizing factory. We characterize the symptomatology, anatomical, and histochemistry alterations induced in the two species. There was no difference in the symptomatology in relation to the different distances of the emitting source. The foliar symptoms found in C. hilariana were chlorosis, necrosis, and foliar abscission and, in E. uniflora, were observed necrosis punctuais, purple spots in the leaves, and increase in the emission of new leaves completely purplish. The two species presented formation of a cicatrization tissue. E. uniflora presented reduction in the thickness of leaf. In C. hilariana, it was visualized hyperplasia of the cells and the adaxial epidermis did not appear collapsed due to thick cuticle and cuticular flanges. Leaves of C. hilariana showed positive staining for iron, protein, starch, and phenolic compounds. E. uniflora showed positive staining for total phenolic compounds and starch. Micromorphologically, there was accumulation of particulate matter on the leaf surface, obstruction of the stomata, and scaling of the epicuticular wax in both species. It was concluded that the visual and anatomical symptoms were efficient in the diagnosis of the stress factor. C. hilariana and E. uniflora showed to be good bioindicators of the atmospheric pollutants emitted by the pelletizing factory.

Ecophysiological responses to excess iron in lowland and upland rice cultivars.

Iron (Fe) is an essential nutrient for plants but under high concentrations, such as that found naturally in clay and waterlogged soils, its toxic effect can limit production. This study aimed to investigate the stress tolerance responses exhibited by different rice cultivars. Both lowland and upland cultivars were grown under excess Fe and hypoxic conditions. Lowland cultivars showed higher Fe accumulation in roots compared with upland cultivars suggesting the use of different strategies to tolerate excess Fe. The upland Canastra cultivar displayed a mechanism to limit iron translocation from roots to the shoots, minimizing leaf oxidative stress induced by excess Fe. Conversely, the cultivar Curinga invested in the increase of R1/A, as an alternative drain of electrons. However, the higher iron accumulation in the leaves, was not necessarily related to high toxicity. Nutrient uptake and/or utilization mechanisms in rice plants are in accordance with their needs, which may be defined in relation to crop environments. Alterations in the biochemical parameters of photosynthesis suggest that photosynthesis in rice under excess Fe is primarily limited by biochemical processes rather than by diffusional limitations, particularly in the upland cultivars. The electron transport rate, carboxylation efficiency and electron excess dissipation by photorespiration demonstrate to be good indicators of iron tolerance. Altogether, these chemical and molecular patterns suggests that rice plants grown under excess Fe exhibit gene expression reprogramming in response to the Fe excess per se and in response to changes in photosynthesis and nutrient levels to maintain growth under stress.

Differential responses of C3 and CAM native Brazilian plant species to a SO2- and SPMFe-contaminated Restinga.

Aiming to evaluate responses in terms of growth rates, physiological parameters, and degree of sensitivity to SO2 and SPMFe in Eugenia uniflora L. (Myrtaceae, a C3 species) and Clusia hilariana Schlecht (Clusiaceae, a CAM species); saplings were exposed to emissions from a pelletizing factory for 7 months. The species were distributed along a transect (200, 500, 800, 1400, and 1700 m away from the emission source), and analyses were performed after 71, 118, and 211 days of exposure to the pollutants. E. uniflora received higher superficial deposition of particulate iron. The highest total iron foliar contents were observed 200 m away from the emission source in both plant species, while the highest total sulfur foliar contents were observed 200 m away in C. hilariana and 800 m away in E. uniflora. E. uniflora presented decreased values of height growth rate, number of necrotic leaves, chlorophyll analysis (SPAD index) and transpiration, in relation to the distances from the emission source. C. hilariana showed decreased values of height growth rate, number of leaves, number of necrotic leaves, total ionic permeability, stomatal conductance, transpiration, net CO2 assimilation, and total dry matter, in relation to distances from the emission source. In relation to the days of exposure, both species presented increased number of necrotic leaves and foliar phytotoxicity index, and decreased values in the chlorophyll analysis. The two native plant species, both of which occur in the Brazilian Restinga, showed damage when exposed to emissions from an iron ore pelletizing factory. C. hilariana was considered the most sensitive species due to the decreased values in a higher number of variables after exposition.

Iron excess affects rice photosynthesis through stomatal and non-stomatal limitations.

Iron toxicity is the most important stressor of rice in many lowland environments worldwide. Rice cultivars differ widely in their ability to tolerate excess iron. A physiological evaluation of iron toxicity in rice was performed using non-invasive photosynthesis, photorespiration and chlorophyll a fluorescence imaging measurements and chlorophyll content determination by SPAD. Four rice cultivars (BR IRGA 409; BR IRGA 412; BRA 041171 and BRA 041152) from the Brazilian breeding programs were used. Fe(2+) was supplied in the nutrient solution as Fe-EDTA (0.019, 4, 7 and 9 mM). Increases in shoot iron content due to Fe(2+) treatments led to changes in most of the non-invasive physiological variables assessed. The reduction in rice photosynthesis can be attributed to stomatal limitations at moderate Fe(2+) doses (4mM) and both stomatal and non-stomatal limitations at higher doses. Photorespiration was an important sink for electrons in rice cultivars under iron excess. A decreased chlorophyll content and limited photochemical ability to cope with light excess were characteristic of the more sensitive and iron accumulator cultivars (BRA 041171 and BRA 041152). Chlorophyll fluorescence imaging revealed a spatial heterogeneity of photosynthesis under excessive iron concentrations. The results showed the usefulness of non-invasive physiological measurements to assess differences among cultivars. The contributions toward understanding the rice photosynthetic response to toxic levels of iron in the nutrient solution are also discussed.

Iron plaque formation and morphoanatomy of roots from species of restinga subjected to excess iron.

The restingas, a sandy coastal plain ecosystem of Brazil, have received an additional amount of iron due to the activity of mining industries. The present study aims to characterize morphoanatomically and histochemically the iron plaque formation on roots of Ipomoea pes-caprae L. and Canavalia rosea DC, cultivated in hydroponic solution with and without excess iron. The iron plaque formation as well as changes in the external morphology of the lateral roots of both species were observed after the subjection to excess iron. Changes in the nutrient uptake, and in the organization and form of the pericycle and cortex cells were observed for both species. Scanning electron microscopy showed evident iron plaques on the whole surface of the root. The iron was histolocalized in all root tissues of both species. The species of restinga studied here formed iron plaque in their roots when exposed to excess of this element, which may compromise their development in environments polluted by particulated iron.

Photosynthesis and oxidative stress in the restinga plant species Eugenia uniflora L. exposed to simulated acid rain and iron ore dust deposition: potential use in environmental risk assessment.

The Brazilian sandy coastal plain named restinga is frequently subjected to particulate and gaseous emissions from iron ore factories. These gases may come into contact with atmospheric moisture and produce acid rain. The effects of the acid rain on vegetation, combined with iron excess in the soil, can lead to the disappearance of sensitive species and decrease restinga biodiversity. The effects of iron ore dust deposition and simulated acid rain on photosynthesis and on antioxidant enzymes were investigated in Eugenia uniflora, a representative shrub species of the restinga. This study aimed to determine the possible utility of this species in environmental risk assessment. After the application of iron ore dust as iron solid particulate matter (SPM(Fe)) and simulated acid rain (pH 3.1), the 18-month old plants displayed brown spots and necrosis, typical symptoms of iron toxicity and injuries caused by acid rain, respectively. The acidity of the rain intensified leaf iron accumulation, which reached phytotoxic levels, mainly in plants exposed to iron ore dust. These plants showed the lowest values for net photosynthesis, stomatal conductance, transpiration, chlorophyll a content and electron transport rate through photosystem II (PSII). Catalase and superoxide dismutase activities were decreased by simulated acid rain. Peroxidase activity and membrane injury increased following exposure to acid rain and simultaneous SPM(Fe) application. Eugenia uniflora exhibited impaired photosynthetic and antioxidative metabolism in response to combined iron and acid rain stresses. This species could become a valuable tool in environmental risk assessment in restinga areas near iron ore pelletizing factories. Non-invasive evaluations of visual injuries, photosynthesis and chlorophyll a fluorescence, as well as invasive biochemical analysis could be used as markers.

Trioecy in Coccoloba cereifera Schwacke (Polygonaceae), a narrow endemic and threatened tropical species

Trioecy, the co-occurrence of the males, females, and hermaphrodite morphs in natural populations, is a rare and poorly studied breeding system. It is expressed in Coccoloba cereifera, an endemic, and endangered species from the rupestrian fields of Serra do Cipó, southeastern Brazil. Male individuals produce staminate flowers but no fruits. Female individuals produce pistillate flowers and set fruits. Both staminate and pistillate flowers present non-functional organs of the opposite sex that simulate perfect flowers. Hermaphrodite individuals produce two different perfect flowers, each one belonging to distinct individuals, and set fruits. Perfect flowers differ in the amount of pollen produced, in pollen viability, and in some morphological traits. Two Hymenoptera species visited the flowers sporadically. The low natural fructification indicated a limited pollination, while the fruit set recorded in bagged pistillate flowers indicated agamospermy. Female individuals represent more than 40 percent of the population studied and must be the result of agamospermic seeds.

A trioicia, a coocorrência, em população natural, de indivíduos masculinos, femininos e hermafroditas, é um sistema reprodutivo raro e pouco estudado. Coccoloba cereifera (Polygonaceae), espécie endêmica e em perigo de extinção dos campos rupestres da Serra do Cipó, sudeste brasileiro, apresenta esse sistema. Indivíduos masculinos produzem flores estaminadas e não frutificam. Indivíduos femininos produzem flores pistiladas e frutificam. Ambas flores estaminadas e pistiladas apresentam órgãos não-funcionais do sexo oposto, tornando-as semelhantes às flores perfeitas. Indivíduos hermafroditas produzem dois tipos de flores perfeitas, cada um pertencente a indivíduos distintos, e ambos frutificam. As flores perfeitas diferem entre si na quantidade de pólen produzido, na viabilidade do pólen e em algumas características morfológicas. Duas espécies de Hymenoptera visitaram as flores esporadicamente. A baixa frutificação natural indicou uma polinização limitada, ao passo que a frutificação registrada em flores pistiladas, isoladas por sacos, indicou agamospermia. Indivíduos femininos representaram mais que 40 por cento da população estudada e devem ser resultantes de sementes agamospérmicas.

Effects of simulated deposition of acid mist and iron ore particulate matter on photosynthesis and the generation of oxidative stress in Schinus terebinthifolius Radii and Sophora tomentosa L.

Particulate matter is a natural occurrence in the environment, but some industries, such as the iron ore sector, can raise the total amount of particles in the atmosphere. This industry is primarily a source of iron and sulfur dioxide particulates. The effects of the pollutants from the iron ore industries on representatives of restinga vegetation in a Brazilian coastal ecosystem were investigated using physiological and biochemical measures. Two species, Schinus terebinthifolius and Sophora tomentosa, were exposed to simulated deposition of acid mist and iron ore particulate matter in acrylic chambers in a greenhouse. Parameters such as gas exchange, fluorescence emission, chlorophyll content, total iron content, antioxidant enzyme activity and malondialdehyde content were assessed in order to evaluate the responses of the two species. Neither treatment was capable of inducing oxidative stress in S. terebinthifolius. Nevertheless, the deposition of iron ore particulates on this species increased chlorophyll content, the maximum quantum efficiency of photosystem II and the electron transport rate, while iron content was unaltered. On the other hand, S. tomentosa showed a greater sensitivity to the treatments. Plants of S. tomentosa that were exposed to acid mist had a decrease in photosynthesis, while the deposition of iron particulate matter led to an increase in iron content and membrane permeability of the leaves. The activities of antioxidant enzymes, such as catalases and superoxide dismutase, were enhanced by both treatments. The results suggested that the two restinga species use different strategies to overcome the stressful conditions created by the deposition of particulate matter, either solid or wet. It seems that while S. terebinthifolius avoided stress, S. tomentosa used antioxidant enzyme systems to partially neutralize oxidative stress. The findings also point to the potential use of S. tomentosa as a biomarker species under field conditions.

Effects of fluoride emissions on two tropical grasses: Chloris gayana and Panicum maximum cv. Colonião.

In order to detect early effects of plant contamination by fluoride emission on two tropical grasses, Chloris gayana and Panicum maximum, previously cultivated under greenhouse conditions, were exposed to a single source of fluoride emission at a station at 1.1 km from an aluminum smelter in Ouro Preto, MG, Brazil. Controls were placed at a reference station 78km from the fluoride source. During an 8-day period of exposure leaf injury, ionic permeability, photosynthetic rates, stomatal conductance, transpiration, chlorophyll a fluorescence and chlorophyll, soluble carbohydrates and fluoride contents were evaluated. Plants at the Ouro Preto station showed an increase in fluoride content, leaf injury and ionic permeability. Symptoms of injury by fluoride exposure were visible after 3-4 days in both species. High electrolyte leakage and correlation coefficients between the total ionic permeability and the fluoride content in leaves indicate a fluoride effect on the structural and/or functional integrity of the cellular membranes. Leaf fluoride injuries were quite different in the two species. In C. gayana necroses were limited to the leaf tips, while in P. maximum damages were observed in the whole leaf, suggesting a higher susceptibility of this latter species to fluoride. Nonetheless, neither grass showed statistical differences with respect to photosynthetic rates, stomatal conductance, transpiration, chlorophyll a fluorescence and chlorophyll content in leaves without any apparent fluoride injury. Plants at the Ouro Preto station showed a significant decrease in reducing sugar content between 3 and 5 days of exposure to fluoride, but thereafter reducing sugar content increased reaching the content of control plants. Fluoride exposed plants also showed a remarkable starch content reduction, remaining always much lower than those at the reference station.