Effect of UV-B priming on the abiotic stress tolerance of stress-sensitive rice seedlings: Priming imprints and cross-tolerance

Ultraviolet (UV)-B priming can boost the abiotic stress tolerance of plants by activating stress-responsive pathways. The main objective of the present study was to investigate the persistence of priming imprints and cross-tolerance inducing effects of UV-B priming in abiotic stress-sensitive rice (Oryza sativa L. 'Aiswarya') when subjected to various abiotic stressors (NaCl, PEG, and UV-B). The UV-B priming of rice seeds and seedlings effectively enhanced photosynthetic efficiency, antioxidant machinery activity, and antioxidative enzyme production, especially when seedlings were exposed to NaCl, followed by UV-B and PEG. The ability of UV-B priming to induce cross-tolerance against NaCl stress was substantiated by the greater antioxidant activity of the primed and NaCl-stressed seedlings. The greater performance and stress tolerance of the seedlings from UV-B-primed seeds were attributed to the carryover of priming imprints from seeds into the seedlings. Indeed, UV-B priming activated the antioxidant systems of the seedlings, even under non-stress conditions, and resulted in greater responses upon subsequent stress exposure, which suggested that preparedness for encountering imminent stress was attained by UV-B priming in a stress-sensitive rice.