Physiological and Molecular Responses of the Aboveground Part of Indica-Japonica Intersubspecific Tetraploid Rice Seedlings to Ion Beam Stress

Low-energy ion beam bombardment can induce various biological effects on plants, including stimulation, damage, and mutation. However, the physiological and molecular mechanisms of the biological effects of ion implantation are not fully understood. In this article, ion beam implantation was performed on Indica–Japonica intersubspecific tetraploid rice seeds to explore the responses of their seedlings. The investigation found that the aboveground part development of rice seedlings was inhibited, radiation damage was induced, and the metabolic accumulation and expression of abscisic acid (ABA) was disturbed by implantation with large doses of the low-energy $\text{N}^{+}$ beam. The activities of the antioxidant enzymes and proline (Pro) content were also increased by low-dose ion implantation induction. The malondialdehyde (MDA) content in seedlings under ion implantation was markedly higher than those of controls, and increased with the increase of ion beam irradiation doses. Transcriptional expression analysis of selected genes revealed that partly ABA anabolism genes associated with ABA production were significantly upregulated in seedlings in response to ion implantation. The aforementioned results will be useful for further research on the physiological and molecular mechanisms of Indica–Japonica intersubspecific tetraploid rice to ion beam stress.