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

Abstract

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.

Oxidative damage and photosynthetic impairment in tropical rice cultivars upon exposure to excess iron

“…The oxidative damage, as indicated by the TBARS concentration in the sensitive cultivar, may disrupt the membrane integrity of the thylakoid and hinders the formation of a transmembrane electrochemical potential gradient in the chloroplasts through lipid peroxidation, preventing NPQ buildup. The susceptibility of NPQ to high Fe concentrations in leaves has been reported previously (Neves et al, 2009;Pereira et al, 2013).…”

“…Although chlorophyll molecules may be degraded by ROS (Neves et al, 2009), these pigments were not the first target of ironinduced oxidative stress. On the other hand, iron is required for chlorophyll biosynthesis (Msilini et al, 2011), and the chlorophyll index may increase in plants that are exposed to an iron overload (Pereira et al, 2013).…”

Assessment of Iron Toxicity in Tropical Grasses with Potential for Revegetating Mined Areas

“…The absorption and excessive accumulation of iron in plants can increase the formation of rOS, therefore causing oxidative damage in plants [4,25]. Increases in MDA, a lipid peroxidation byproduct, are considered an important indicator of oxidative stress in plants [13,26].…”

Effects of road dust on the growth characteristics of Sophora japonica L. seedlings

“…In previous artificial dusting studies, several dust load treatments were compared (Armbrust, 1986;Shukla et al, 1990;Charlesworth et al, 2003;Kuki et al, 2009), concerning loam, fly ash, iron dust, and cement dust. As for the dust composition's effects on plants, in the ore dust studies, ore element contents and plant characteristics were often linked (Kuki et al, 2008;Neves et al, 2009). However, comparison is lacking for the ways dusts of different compositions affect plants.…”