Enhancement of root growth under salt stress through the application of β-cyclocitral derivatives DQC-8 in Oryza sativa L.

Soil salinization is a major constraint to crop productivity, necessitating new strategies to enhance stress tolerance in staple cereals like rice (Oryza sativa L.). Although β-cyclocitral is a promising plant metabolite for promoting root growth under salt stress, its volatility and instability limit practical use. Here, we synthesized and screened a series of β-cyclocitral derivatives, identifying the acyl hydrazone DQC-8 as an optimized candidate. Under moderate salt stress (100 mM NaCl), DQC-8 treatment increased primary root length by 61% and plant biomass by up to 24% in 9311 rice compared with untreated controls, without affecting normal growth under non-stress conditions. In Nipponbare rice under high salt stress (150 mM NaCl), DQC-8 also increased primary root length by 23%. Furthermore, DQC-8 treatment improved all major agronomic traits in Nipponbare rice grown in salt-contaminated soil. Regarding to stability in water, DQC-8 retained over 30% of its concentration after 31 days in solution, whereas β-cyclocitral activity declined to 0.42% after 6 days. Mechanistic analyses revealed that DQC-8 mitigates salt-induced oxidative damage by reducing reactive oxygen species accumulation and proline content, thereby preserving cell membrane integrity. Transcriptome profiling demonstrated that DQC-8 modulates multiple key stress-responsive genes and pathways, notably upregulating OsPAO4, OsPYL6, OsERF096, DREB1C, and OsHSFA9, which contribute to enhanced adaptive responses. Collectively, these findings establish DQC-8 as a stable and efficacious plant growth regulator with significant potential for improving rice resilience on saline-alkali soil.