Evaluation of changes in lipid peroxidation, ROS production, surface structures, secondary metabolites and yield of linseed (Linum usitatissimum L.) under individual and combined stress of ultraviolet-B and ozone using open top chambers.

The individual and interactive effects of supplemental UV-B (sUV-B) (ambient + 7.2 kJ m-2 d-1) and elevated O3 (ambient + 10 ppb) were evaluated under field conditions using open top chambers on two cultivars, Padmini and T-397 of linseed (Linum usitatissimum L.). Mean monthly surface level of O3 concentrations varied from 27.7 ppb to 59.0 ppb during the experimental period. Both UV-B and O3 induced the production of ROS (H2O2 and O2.-), resulting in significant damage of membranes due to lipid peroxidation and electrolyte leakage. Synthesis of secondary metabolites (flavonoids, anthocyanin, lignin and wax) was also enhanced in all the treatments, whereas biomass and yield were reduced. Alterations in frequency of stomata and wax distribution were also observed through scanning electron microscopy (SEM). Cultivar Padmini was found to be more sensitive because of higher damage of membrane vis-a-vis reduction in biomass and seed yield. However, concentrations of flavonoids, anthocyanin, lignin and wax were higher in T-397, suggesting its relative resistance against applied stress. Combined exposure of sUV-B and O3 was less harmful, as compared to their individual treatment. Among the three treatments, O3 was found to be more detrimental for overall growth and sUV-B for economic yield.

Adaptive Responses Induced by Low Dose Radiation in Dentate Gyrus of Rats

The purpose of this study is to investigate the mechanism of alternative responses to low dose irradiation for neuronal cell proliferation in the dentate gyrus of rats. To determine the effect of a single exposure to radiation, rats were irradiated with a single dose of 0.1, 1, 10 or 20 Gy. To determine the effect of the cumulative dose, the animals were irradiated daily with 0.01 Gy or 0.1 Gy from 1 to 4 days. The neuronal cell proliferation was evaluated using immunohistochemistry for 5-bromo-2'-deoxyuridine (BrdU), Ki-67 and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining. Four consecutive daily irradiations with a 0.01 Gy/fraction increased the number of BrdU-positive and Ki-67-positive cells in a dose dependent manner, but this did not affect the number of TUNEL-positive cells. However, there was not a dose dependent relationship for the 0.1 Gy/fraction irradiation with the number of BrdU, Ki-67 and TUNEL positive cells. Our data support the explanation that the adaptive response, induced by low-dose radiation, in the hippocampus of rats is more likely a reflection of the perturbations of cell cycle progression.