Mn₃ O₄ Nanoparticles Alleviate ROS-Inhibited Root Apex Mitosis Activities to Improve Maize Drought Tolerance

Poly (acrylic) acid coated Mn3O4 nanoparticles (PAA@Mn₃ O₄ nanoparticles (PMO, 11.02 nm, -28.93 mV)) are synthesized to investigate whether they can help to improve maize drought tolerance and the relevant mechanisms behind this. In planta experimental results show that under drought (15% PEG 6000, polyethylene glycol, mimicking drought stress, 96 h), compared with the control plants, 500 mg L^-1 PMO (root application, 96 h) improves maize drought tolerance, showing an increase of root length (21.6%), shoot length (21.2%), fresh weight (7.8%) and total protein (67.2%) content. In addition, PMO significantly decreases the malondialdehyde (MDA) content by 74.7% in maize under drought, compared with the control group. Further, PMO treated maize root apex shows significantly increased mitotic index (MI, 35.5%), and decreased hydrogen peroxide (40.9%). Compared with the control under drought (15% PEG, 96 h), thr root apex of maize plants treated with PMO (500 mg L^-1 , root application, 96 h) have significantly lower level of H₂ O₂ . Overall, the results show that PMO can alleviate drought-inhibited cell mitosis activities via maintaining ROS (reactive oxygen species) homeostasis. In this study, it is not only shown that PMO can be a good nano-regulator candidate to improve maize drought tolerance, but also that PMO has potential to modulate plant cell mitosis activities.