Influence of Ionizing Radiation on Antioxidant Enzymes in Three Species of Trigonella (Report‪)‬

INTRODUCTION Plants often face the challenge of several environmental conditions which include such stressors as drought, salinity, pesticides, low temperature and irradiation, all of which exert adverse effects on plant growth and development (1). Gamma irradiation was reported to induce oxidative stress with overproduction of reactive oxygen species (ROS) such as superoxide radicals ([O.sub.2.sup.-]), hydroxyl radicals ([OH.sup.-]) and hydrogen peroxides ([H.sub.2][O.sub.2]) (2), which react rapidly with almost all structural and functional organic molecules, including proteins, lipids and nucleic acids causing disturbance of cellular metabolism (3). To avoid oxidative damage, plants have evolved various protective mechanisms to counteract the effects of reactive oxygen species in cellular compartments (4). One of the protective mechanisms was the enzymatic system, which operate with the sequential and simultaneous actions of a number of enzymes including SOD, APOX and CAT (5). SOD which occur in various cell compartments, dismute [O.sub.2.sup.-] to [H.sub.2][O.sub.2] and oxygen (6). Catalases were synthesized in a tissue specific and age dependent manner, scavenge [H.sub.2][O.sub.2] generated during photorespiration and [beta]-oxidation of fatty acids (7). Peroxidases located in the cytosole, vacuole, cell walls as well as in extra-cellular spaces use guaiacol as electron donors and utilize [H.sub.2][O.sub.2] in the oxidation of various inorganic and organic substrates (8). The role of GR in [H.sub.2][O.sub.2] scavenging mechanism in plant cells was well established in Haliwell--Asada enzyme pathways (4).