Resilience of oilseed rape plants to drought stress after exogenous application of AM1, an ABA-mimicking ligand

AM1 (ABA-mimicking ligand) is a newly identified signaling molecule for plants during drought tolerance. To investigate the potential role of AM1 in response of rapeseed to drought stress, we conducted experiments by growing rapeseed plants under different levels of drought stress with or without applying AM1 or ABA in a rain shelter. The results indicated that drought significantly inhibited rapeseed growth by damaging the photosynthesis system, increasing active oxygen accumulation, destroying the oxidative system, and worsening membrane lipid peroxidation. Exogenously applied AM1 and ABA both relieved the damage to rapeseed that was induced by drought stress. Compared with the drought-treated rapeseed, the AM1 treatment significantly improved plant height, number of green leaves, root collar thickness, leaf area, dry matter weight, and root cap ratios of rapeseed. In addition, Pn, Gs, Ci, Tr were significantly increased by the AM1 treatment. The AM1 treatment also alleviated the drought-induced reductions in Fv/Fm, ΦPSII, qN and ETR; induced an increase in NPQ; and resulted in decreased active oxygen accumulation and membrane lipid peroxidation. Although the ABA treatment relieved photosynthetic fluorescence and antioxidation system parameters to some extent, the effect was inferior to AM1 treatment. Yield under AM1 treatment was higher than that under ABA treatment but was still far lower than that of normal water supply control. In summary, AM1 is functionally similar to ABA in terms of drought relief and regulation, moreover has a better effect.