Electron Beam Ionization Induced Oxidative Enzymatic Activities in Pepper (Capsicum annuum L.), Associated with Ultrastructure Cellular Damages

Abstract

Mature green pepper fruits (Capsicum annuum L.) were subjected to ionizing radiation, in the range of 1-7 kGy, with accelerated electrons. Ultrastructural changes by electron microscopy, and the activity of several oxidative metabolism-related enzymes such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaicol peroxidase (POX), and lipoxygenase (LOX), were determined in pericarp tissue just after the ionization treatment and during postionization storage at 7 degrees C followed by 3 days at 20 degrees C. Changes in oxidative stress during the ionization treatment was assessed by the accumulation of malondyaldehide (MDA), a lipid peroxidation product. The ionization induced modifications in the cell ultrastructure, a moderate separation of the plasma membrane from the cell wall being observed for all doses. At 5 and 7 kGy, peroxisomes were not detected and the structures of the chloroplast and vacuoles were seriously damaged. Lipid peroxidation and lipoxygenase activity increased with the ionization dose, staying constant and decreasing, respectively, during the storage period. Conversely, catalase, ascorbate peroxidase, and superoxide dismutase had lower values than in nonionized fruits and, in general, their values did not change or diminished slightly from the seventh day of storage. Peroxidase exhibited an increase in activity with the ionization dose, although these was not a linear relationship, with higher values at 3kGy. Ionization of pepper, especially at doses of 5 and 7 kGy, caused a significant oxidative damage in the fruit, since it increased oxidation and decreased the antioxidant enzymatic defense systems causing ultrastructural changes at cell level.

Anatomical alterations of Phaseolus vulgaris L. mature leaves irradiated with X‐rays

“…The number of chloroplasts per cell, chloroplast ultrastructure, and pigment content have all been reported to be sensitive to irradiation (Keresztes & Kovács ; Martínez‐Solano et al . ; Kim et al . ).…”

“…Perturbations in the photosynthetic machinery have been observed in plants subjected to ionising radiation, with photosynthetic impairment detected at different steps of the photosynthetic pathway (De Micco et al 2011a). The number of chloroplasts per cell, chloroplast ultrastructure, and pigment content have all been reported to be sensitive to irradiation (Keresztes & Kov acs 1991;Mart ınez-Solano et al 2005;Kim et al 2011). However, many modifications seem to depend on the age of leaves at the time of irradiation.…”

Antioxidant response of Arabidopsis plants to gamma irradiation: Genome-wide expression profiling of the ROS scavenging and signal transduction pathways

“…ROS scavenging is a common protective response against gamma irradiation. The gamma irradiation responses of the four antioxidant enzymes, POD, APX, CAT and SOD, all of which are induced by water radiolysis (De Vita et al, 1993;Martinez-solano et al, 2005), were assessed in the 100 Gy and 800 Gy irradiated plants at both stages. Changes in POD activity as a consequence of gamma irradiation are shown in Fig.…”

Alcohol‐induced oxidative stress and cell responses

“…Normally, ROS are produced from endogenous sources as by‐products of normal and essential metabolic reactions, such as mitochondria energy generation or the detoxification reactions involving the cytochrome P‐450 enzyme system 19 . Exogenous sources include exposure to cigarette smoke, 20 consumption of alcohol in excess 13 and exposure to ionizing radiation 21 . Reactive oxygen species are able to (i) cause permanent structural changes in DNA as base‐pair mutations, deletions, insertions, rearrangements, and sequence amplification; (ii) initiate lipid peroxidation; (iii) activate cytoplasmic and nuclear signal transduction pathways; and (iv) modulate the activity of stress proteins and stress genes that regulate effector genes related to growth, differentiation, and cell death.…”