Photosynthetic changes and oxidative stress caused by iron ore dust deposition in the tropical CAM tree Clusia hilariana

Abstract

The effect of iron solid particulate matter (SPM Fe ) deposited onto soil and leaves on photosynthesis and oxidative stress was evaluated in Clusia hilariana, a CAM tropical tree of high occurrence in Brazilian restingas. Significant increases in iron content were found in plants exposed to SPM Fe applied onto leaf and soil surfaces. However, only the application of SPM Fe on leaves of C. hilariana caused significant reductions in some evaluated characteristics such as photosynthetic rate, stomatal conductance, transpiration, organic acid accumulation, potential quantum yield of PSII, and changes in daily CAM photosynthesis pattern. Increase in relative membrane permeability and reduction in catalase and superoxide dismutase activities in the leaves of plants exposed to SPM Fe also were observed; however, lipid peroxidation did not change. These responses seem to be due to the combination of physical effects such as increase of leaf temperature, reduction in light absorption, obstruction of stomatal pores, and biochemical effects triggered by oxidative stress.

Early detection of injuries in leaves of Clusia hilariana Schltdl. (Clusiaceae) caused by particulate deposition of iron

“…In previous studies, asymptomatic leaves of this species showed physiological alterations in response to the SPM Fe deposition, such as reduction of the pigment levels, compromising of the photosynthetic processes, and the increase of the leaf iron level (PEREIRA et al, 2009). Among possible causes, the authors have suggested it was due to the obstruction of the stoma and the iron absorption of the iron at leaf level, as the soil was covered during the SPM Fe applications (PEREIRA et al, 2009). However, the leaf structural and micromorphological analyses can be the key for answering these questions.…”

“…The experiment lasted 45 days, and the deposition simulation was performed at 8:00 in the morning. Inside the chamber, the amount of particulate matter deposited on the plants reached an average of 2.14 mg cm -2 day -1 (PEREIRA et al, 2009). In the control treatment, the plants were not subjected to deposition of iron particulate.…”

“…The simulation experiment was performed in a greenhouse (average annual temperature of 27.6ºC; average relative humidity of 72%) at the Universidade Federal de Viçosa (UFV) (20° 45' 20'' S, 42° 52' 40'' W), by means of a chamber that create natural ore deposition, as proposed by Hirano et al, (1995), and modified by Pereira et al, (2009). Before the simulation, C. hilariana plants were standardized regarding their height uniformity, number of leaves, and phytosanitary state.…”

“…The deposition of particulate matter on the leaf surface causes blockage of solar radiation by shadowing the leaf surface, altering the pigment synthesis, and the photosynthetic rate (HIRANO et al, 1995;NAIDOO;CHIRKOOT, 2004;OLIVEIRA et al, 2007;KUKI et al, 2008b;PEREIRA et al, 2009). Additionally, the obstruction of the stoma may cause the increase of the leaf temperature, the alteration of the transpiratory rate (PEREIRA et al, 2009) and anatomical and ultrastructural modifications in leaf tissues organization (SILVA et al, 2006).…”

“…Additionally, the obstruction of the stoma may cause the increase of the leaf temperature, the alteration of the transpiratory rate (PEREIRA et al, 2009) and anatomical and ultrastructural modifications in leaf tissues organization (SILVA et al, 2006). Symptomatological, physiological, and biochemical parameters have been often used to evaluate the effects of the SPM Fe deposition on plant species (LOPES et al, 2000;OLIVEIRA et al, 2007;KUKI et al 2008a,b;NEVES et al, 2009;PEREIRA et al, 2009). However, little attention has been paid to the prognostic value of microscopic parameters.…”