Photocaged abscisic acid enhances rice salt tolerance <i>via</i> sustained signaling and multilevel stress modulation

BACKGROUND: Although abscisic acid (ABA) is essential for improving plant tolerance to salt stress, its practical use in agriculture is severely limited by rapid photodegradation, poor lipophilicity, and short-lived activity. Here, three photo-caged ABA derivatives were developed as light-responsive ABA delivery systems and systematically compared with free ABA. RESULTS: All three photo-caged ABA derivatives showed sustained bioactivity in seed germination assays of Arabidopsis thaliana and rice, indicating prolonged ABA action. Under salt stress, NV (4,5-dimethoxy-2-nitrobenzyl bromide4)-ABA performed best. Compared with free ABA, NV-ABA enhanced seedling salt tolerance, promoted chlorophyll recovery, and increased shoot and root fresh weights by 36% and 18%. It also better maintained antioxidant homeostasis and moderate ABA signaling. Sustained expression of OsP5CS1, OsP5CR, OsNHX1, and OsRAB16A supported prolonged stress regulation. CONCLUSION: This study developed a photo-controlled strategy for precise ABA delivery, improving ABA stability and utilization, prolonging bioactivity, and enhancing crop salt tolerance, thus providing a novel approach for ABA application in crop stress regulation. © 2026 Society of Chemical Industry.