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

Variation in Brant's oak (Quercus brantii Lindl.) leaf traits in response to pollution from a gas refinery in semiarid forests of western Iran

Air pollution around refineries and factories is one of the major environmental challenges affecting forest ecosystems' health. Although there have been many studies on Iran's forest ecosystems, the physiological and morphological responses of Brant's oak (Quercus brantii Lindl.) leaves to the pollution of the gas refineries in the semiarid forests have not received much attention. We sampled healthy and mature leaves from four oak stands in different seasons (spring, summer, and autumn of 2019) and at various distances from the gas refinery (1,000, 1,500, 2,000, 2,500, and 10,000 m). The results showed that oak trees in different seasons and at different distances from the refinery had different physiological and morphological leaf trait responses to the pollution source. Oak trees with an air pollution tolerance index value of less than 11 were in a sensitive range to air pollution and can be used to biomonitor air pollution around the gas refinery in Zagros forests. Physiological traits in different seasons and at various distances in comparison with morphological traits (persistent reaction responses) were well distinguished from one another and were more affected by pollution. Oak trees in summer and autumn and at distances up to 2,500 m had rapid reaction responses, including oxidative stress indicators such as electrolyte leakage (EL), hydrogen peroxide, and different enzymatic and nonenzymatic antioxidants such as phenol, flavonoids, catalase, and proline. Because of their high sensitivity to atmospheric pollutant stresses, we recommend that these traits be used for rapid and low-cost environmental monitoring of pollution in different seasons and distances from pollution sources in semiarid ecosystems.

Biomarker Responses of Spanish Moss Tillandsia usneoides to Atmospheric Hg and Hormesis in This Species

Hg is an environmental pollutant with severe biotoxicity. Epiphytic Tillandsia species, especially Spanish moss T. usneoides, are widely used as the bioindicator of Hg pollution. However, the effects of different Hg concentrations on Tillandsia have been rarely studied and the occurrence of hormesis in Tillandsia species has not been determined. In this study, T. usneoides was subjected to stress induced by 15 concentrations of gaseous Hg ranging from 0 to 1.8 μg m^-3 through a misting system and then Hg content and eight common biomarkers in leaves were measured. The results showed that leaf Hg content significantly increased with Hg concentration, showing a linear relationship. However, there were no obvious mortality symptoms, indicating that T. usneoides showed strong resistance to Hg. Conversely, there were no simple linear relationships between changes in various biomarkers following Hg treatment of T. usneoides and Hg concentration. With increasing Hg concentration, malondialdehyde (MDA) content did not change significantly, superoxide anion radical content decreased gradually, superoxide dismutase (SOD) content decreased to the bottom and then bounced back, electrical conductivity increased, and glutathione (GSH) and metallothionein (MT) content increased to the peak and then dropped. The coefficient of determination of the dose-effect curves between SOD, GSH, and MT contents and Hg concentration was high, and the dose-effect relationship varied with hormesis. The present study is first to confirm hormesis induced by heavy metal pollution in Tillandsia species.

Physiological response of the bioindicator Ramalina farinacea in relation to atmospheric deposition in an urban environment

Urban air pollution is one of the most important environmental problems. Lichens are good bioindicators in air pollution studies because of their dependence on the atmospheric deposition for nutrition. The present study focused on the effects of urbanization on the composition of atmospheric deposition inputs and physiological parameters of transplanted epiphytic lichen Ramalina farinacea. The status of lichens responded to urban pollutants related to vehicle and industrial activity (NO₃^-, Ca²⁺, Mg²⁺, NO₂, PM₁₀). The content of chlorophyll and F_V/F_M were positively related to the amount of precipitation (mm) and the Normalized Difference Vegetation Index (NDVI). The increase in lipid peroxidation and electrolyte conductivity, indicating damage to the cell membrane, was found in lichens transplanted to the urban environment. The high variability in electrolyte conductivity indicated that cell membrane injuries were characteristics of the investigated study area.

The utility of biochemical, physiological and morphological biomarkers of leaf sulfate levels in establishing Brachylaena discolor leaves as a bioindicator of SO2 pollution

The negative impacts of air pollution have made monitoring of air quality increasingly important, especially in heavily industrialized areas such as the South Durban Basin (SDB), in South Africa. Bioindicators such as trees can complement conventional air quality monitoring and be used to prioritise vulnerable areas. This study assessed the utility of Brachylaena discolor DC. tree leaves as a bioindicator of sulfur dioxide pollution. This involved correlating ground level sulfur dioxide concentrations ([SO₂]) with B. discolor leaf sulfate concentrations ([sulfate]) at three industrial (treatment) sites within the SBD and control site at which [SO₂] was significantly lower for all four seasons. Based on this significant positive correlation between the aforementioned (p = 0.005; ρ = 0.667) leaf sulfate levels were related to various biochemical (intracellular hydrogen peroxide production, total aqueous [TAA] and enzymic antioxidants [superoxide dismutase and catalase], lipid peroxidation [LPO] and electrolyte leakage), physiological (leaf chlorophyll fluorescence [LCF] and relative chlorophyll content) and morphological (leaf area [LA]) biomarkers of stress measured on leaves from trees at the treatment and control sites. Annual [SO₂] and leaf [sulfate] at the treatments were significantly (p < 0.05) higher than the control and high by global standards. TAA, LPO, electrolyte leakage, LCF, and LA were significantly (p < 0.05) correlated with seasonal [sulfate]. Except for superoxide dismutase, catalase and relative chlorophyll content all other biomarkers could differentiate between the treatment sites and the control. However, TAA, electrolyte leakage and LA were the only biomarkers sensitive enough to reflect differences in annual [sulfate] across the treatment sites; these should be used to establish B. discolor leaves as a bioindicator of SO₂ pollution.

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.