Effects of Low Dose γ-Radiation on Photosynthesis of Red Pepper (Capsicum annuum L.) and the Reduction of Photoinhibition

The effect of low dose radiation on photosynthesis and the reduction of photoinhibition in red pepper plant was investigated. The seedling height leaf width and leaf length of pepper were stimulated in plants grown from seeds irradiated with the low dose of 4 Gy. The evolution in the 4 Gy irradiation group was 1.5 times greater than in the control. To investigate the effect of low dose radiation on response to high light stress, photoinhibition was induced in leaves of pepper by illumination of high light (900 ). Pmax was decreased with increasing illumination time by 20% in the control, while hardly decreased in the 4 Gy irradiation group. The photochemical yield of PSII, estimated as Fv/Fm, was decreased with increasing illumination time by 50% after 4 hours while Fo did not change. However, Fv/Fm in the 4 Gy irradiation group was decreased by 37% of inhibition, indicating that the photoinhibition was decreased by the low dose radiation. Changes in the effective quantum yield of PSII, , and 1/Fo-1/Fm, a measure of the rate constant of excitation trapping by the PSII reaction center, showed similar pattern to Fv/Fm. And NPQ was decreased after photoinhibitory treatment showing no difference between the control and the 4 Gy irradiation group. These results showed the positive effect of low dose radiation on the seedling growth and the reduction of photoinhibition.