Ecotoxicological assessments of atmospheric biomonitors exposed to urban pollution in a Brazilian metropolis.

Subcellular metal distribution assessments are the most adequate biomonitoring approach to evaluate metal toxicity, instead of total metal assessments This study aimed to assess subcellular metal distributions and associations to the main metal exposure biomarker, metallothionein (MT), in two bromeliad species (Tillandsia usneoides and Tillandsia stricta) exposed established in industrial, urban, and port areas in the metropolitan region of Rio de Janeiro, southeastern Brazil, through an active biomonitoring approach conducted one year. Metals and metalloids in three subcellular fractions (insoluble, thermolabile and thermostable) obtained from the MT purification process were determined by inductively coupled plasma mass spectrometry (ICP-MS). Lower MT concentrations were observed both during the dry sampling periods, associated to the crassulacean acid metabolism (CAM) and during the COVID-19 pandemic, due to reduced urban mobility, decreasing pollutant emissions. The percentage of non-bioavailable metals detected in the insoluble fraction increased throughout the sampling period for both species. Several metals (Cr, Co, Cu, Cd, Mn, Ni, Se, and Zn), most associated with vehicle emissions, the main pollutant source in urban centers, were detected in the thermostable fraction and are, thus, associated with MT through the MT-metal detoxification route. Insoluble metal concentrations were higher in T. stricta, indicating that this species seems less susceptible to cellular metal exposure damage. A potential protective effect of Se and Fe was detected against Pb, suggested by a strong negative correlation, which may be attributed to antioxidant roles and similar uptake routes, respectively.

Genetic and physiological effects of the natural radioactive gas radon on the epiphytic plant Tillandsia brachycaulos.

Radon (222Rn) is the most abundant natural radioactive gas in nature and triggers carcinogenesis. Few reports exist on whether radon can damage plants as it does animals. Therefore, we chose Tillandsia brachycaulos, a common indicator plant, as the material to detect the physiological and genetic changes caused by radon. With an increase in radon concentration, DNA indices (tail length, tail DNA, tail moment and Olive tail moment) from the comet assay and malondialdehyde (MDA) content increased significantly, suggesting that T. brachycaulos inevitably suffered from radiation damage. However, neither the leaf relative conductivity nor the soluble protein content changed significantly with radon fumigation, and no dose-dependent effect existed between the chlorophyll content and radon concentration, indicating that T. brachycaulos had resistance to radon stress. Foliar trichomes most likely excluded the pollutant from plants because DNA damage in T. brachycaulos with trichomes manually removed was considerably greater than that with trichomes. Moreover, the antioxidant enzyme system further reduced the damage of radon to plants because the activity of superoxide dismutase (SOD) increased significantly with the radon concentration.

Comparison of oxidative stress in four Tillandsia species exposed to cadmium.

This is first study comparing four morphologically variable species of the genus Tillandsia and therefore various responses to the cadmium (Cd) action were expected. In accordance, Cd accumulation increased in order Tillandsia fasciculata < Tillandsia brachycaulos < Tillandsia pruinosa < Tillandsia capillaris, reaching 29.6 and 197.4 µg g(-1) DW in first and last species after watering with 2 µM Cd(2+) solution over 30 days. Fluorescence visualization of oxidative stress confirmed increase in ROS and especially elevation in hydroperoxides though no visible symptoms appeared on the plants. At the same time, nitric oxide generation and nitroso-glutathione depletion by Cd treatment were typically observed. Fluorescence staining of Cd using two dyes (PhenGreen and Leadmium) showed that Leadmium fits better with AAS quantification. Macro- and micro-nutrients were not considerably affected except for zinc. Reduced glutathione content was the highest in control T. fasciculata while oxidized glutathione in T. capillaris. Ascorbic acid amount revealed extreme quantitative differences among species and decreased in T. fasciculata only. Free amino acids accumulation was similar among species except for T. capillaris and Cd caused both depletion and increase but without high quantitative differences. Data are explanatively discussed in the context of limited literature related to oxidative stress in epiphytic plants and with general responses of plants to cadmium/heavy metals.

Physiological responses of Tillandsia albida (Bromeliaceae) to long-term foliar metal application.

The impact of 2-month foliar application of cadmium, nickel and their combination (10 µM) on Tillandsia albida was studied. Cadmium caused damage of tissue but assimilation pigments were depressed in Cd+Ni variant only. Stress-related parameters (ROS and peroxidase activities) were elevated by Cd and Cd+Ni while MDA content remained unaffected. Free amino acids accumulated the most in Ni alone but soluble proteins were not influenced. Among phenolic acids, mainly vanillin contributed to increase of their sum in all variants while soluble phenols even decreased in Cd+Ni and flavonols slightly increased in Cd variants. Phenolic enzymes showed negligible responses to almost all treatments. Mineral nutrients (K, Ca, Na, Mg, Fe, and Zn) were not affected by metal application but N content increased. Total Cd or Ni amounts reached over 400 µg g(-1) DW and were not affected if metal alone and combined treatment is compared while absorbed content differed (ca. 50% of total Cd was absorbed while almost all Ni was absorbed). These data indicate tolerance of T. albida to foliar metal application and together with strong xerophytic morphology, use for environmental studies is recommended.

Antioxidant response of three Tillandsia species transplanted to urban, agricultural, and industrial areas.

To evaluate the physiological response of Tillandsia capillaris Ruiz & Pav. f. capillaris, T. recurvata L., and T. tricholepis Baker to different air pollution sources, epiphyte samples were collected from a noncontaminated area in the province of Córdoba (Argentina) and transplanted to a control site as well as three areas categorized according to the presence of agricultural, urban, and industrial (metallurgical and metal-mechanical) emission sources. A foliar damage index (FDI) was calculated with the physiological parameters chlorophyll a, chlorophyll b, malondialdehyde (MDA), hydroperoxyconjugated dienes, sulfur (S) content, and dry weight-to-fresh weight ratio. In addition, electrical conductivity (E-cond), relative water content (RWC), dehydration kinetics (Kin-H(2)O), total phenols (T-phen), soluble proteins (S-prot), and activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase were determined. The parameters E-cond, FDI, SOD, RWC, and Kin-H(2)O can serve as suitable indicators of agricultural air pollution for T. tricholepis and T. capillaris, and CAT, Kin-H(2)O, and SOD can do the same for T. recurvata. In addition, MDA, T-phen, and S-prot proved to be appropriate indicators of urban pollution for T. recurvata. Moreover, FDI, E-cond, and SOD for T. recurvata and MDA for T. tricholepis, respectively, could be used to detect deleterious effects of industrial air pollution.

Mercury persistence in indoor environments in the Amazon region, Brazil.

We evaluated the indoor atmospheric Hg contamination in gold trade shops in two Brazilian cities of the Legal Amazon area using the Spanish moss (Tillandsia usneoides, Bromeliaceae) as a sentinel species. Plants inside plastic cages were exposed to a controlled atmosphere to evaluate the rate of Hg retention over time and then distributed in several stores with different characteristics to enable a relative comparison. Hg concentrations were determined by cold vapor atomic absorption spectrophotometry. Plants exposed in active stores with good air circulation exhibited lower levels. Ex-gold trade shops that were kept closed for long periods exhibited higher values. Stores that have been restored before being transformed into new businesses exhibited lower values than nonrestored ones. Direct measurements suggest that indoor Hg air concentrations were below the threshold limit recommended by the World Health Organization to occupational exposure; nevertheless, restoring ex-gold trade shops could ensure a healthier working environment.

Physiological responses of the CAM epiphyte Tillandsia usneoides L. (Bromeliaceae) to variations in light and water supply.

In an effort to understand the mechanisms that sustain rootless atmospheric plants, the modulation of Crassulacean acid metabolism (CAM) in response to variations in irradiance and water supply was investigated in the epiphyte Tillandsia usneoides. Plants were acclimated to three light regimes, i.e. high, intermediate and low, with integrated photon flux densities (PFD) of 14.40, 8.64 and 4.32 mol m-2 d-1 equivalent to an instantaneous PFD of 200, 100, and 50 mumol m-2 s-1, respectively. Daily watering was then withdrawn from half of the plants at each PFD for 7 d prior to sampling. In response to the three PFD treatments, chlorophyll content increased in plants acclimated to lower irradiances. Light response curves using non-invasive measurements of chlorophyll fluorescence demonstrated that photosystem II efficiency (phi PSII) was maintained in high PFD acclimated plants, as they exhibited a larger capacity for non-photochemical dissipation (NPQ) of excess light energy than low PFD acclimated plants. Net CO2 uptake increased in response to higher PFD, reflecting enhanced carboxylation capacity in terms of phosphoenolpyruvate carboxylase (PEPc) and ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) activities. After water was withdrawn, nocturnal net CO2 uptake and accumulated levels of acidity declined in all PFD treatments, concomitant with increased respiratory recycling of malate. Examining the strategies employed by epiphytes such as T. usneodies to tolerate extreme light and water regimes has demonstrated the importance of physiological mechanisms that allow flexible carboxylation capacity and continued carbon cycling to maintain photosynthetic integrity.