Brassinosteroids interact with nitric oxide in the response of rice root systems to arsenic stress

Brassinosteroids (BRs), an emerging class of phytohormones, affect numerous plant physiological and metabolic processes can improve defense systems to counteract metalloid phytotoxicity. Nitric oxide (NO), a reactive nitrogen species (RNS), behaves as signalling molecule activating cellular responses various environmental conditions. induce NO synthesis through nitrate reductase (NR) synthase (NOS) activities. Arsenite arsenate, inorganic forms the arsenic (As), cause both soil pollution many disorders in plants, including important crops like rice, due oxidative stress generated by imbalance between RNS oxygen (ROS). Rice is very susceptible As toxicity because availability solubility are high flooded paddy fields cultivated areas. The research aims investigate effects BRs on rice root exposed 10-4 M Na2HAsO40.7 H2O [As(V)] or 2.5 × 10-5 NaAsO2 [As(III)], highlighting induced cyto-histological events dissecting role response. A specific concentration (10-7 M) 24-epibrassinolide (24-eBL), exogenously applied BR, increases lateral (LR) formation more than 50% presence As(III) As(V). In addition, eBL attenuates thickening cell walls outermost cortical layers LRs adventitious roots (ARs) reducing ⁓ lignin deposition, while it restores As(v)-altered levels increasing OsNOS1 expression distribution.