State of the Antioxidant System and Photosynthetic Apparatus of Barley after Gamma-Irradiation at Different Growth Stages

In this study investigated changes in antioxidant system and photosystem II (PSII) in spring barley (Hordeum vulgare L.) leaves after acute γ-radiation exposure at four growth stages. Growth stages: 4 leaves unfolded (Z 14) and 5 leaves unfolded (Z 15), 1st node detectable (Z 31), flag leaf sheath extending (Z 41) and 1/4 of inflorescence emerged (Z 53) according to the international phenological Zadox scale. Plants were irradiated with doses of 15, 30, 45, and 60 Gy at a rate of 16 Gy/h. The flavonoids content was observed as the plants grew, reaching maximum values at the stage Z 53; after γ-irradiation no changes in the content at the studied stages were detected. The MDA content at all growth stages varied within the control range. Proline content remained unchanged compared to control values 48 h post-irradiation. Chl a, Chl b, and carotenoids content did not differ from controls 72 h after irradiation at stages Z 14–Z 15, Z 31, and Z 41, however, at stage Z 53, a 36% decrease in pigments in studied doses range was observed. Photosystem II (PS II) proved to be quite resistant to the effects of acute γ-irradiation in the early stages (Z 14–Z 41), with the exception of the stage Z 53, where a decrease chlorophyll fluorescence was observed. The ascorbic acid (AsA) and reduced glutathione (GSH) content, and the total reducing activity index increased (p < 0.05) at stages Z 31, Z 41 and Z 53 after irradiation in the studied doses range relative to the control. Thus, during the first three days after γ-irradiation of barley plants in high doses, activation of the components of the ascorbate-glutathione cycle was noted.