Co-application of 24-epibrassinolide and titanium oxide nanoparticles promotes 'Pleioblastus pygmaeus' plant tolerance to Cu and Cd toxicity by increasing antioxidant activity and photosynthetic capacity and reducing heavy metal accumulation and translocation

The integrated application of nanoparticles and phytohormones was explored in this study as a potentially eco-friendly remediation strategy to mitigate heavy metal toxicity in a bamboo species (Pleioblastus pygmaeus) by utilizing titanium oxide nanoparticles (TiO2-NPs) and 24-epibrassinolide (EBL). Hence, an in vitro experiment was performed to evaluate the role of 100 uM TiO2 NPs and 10E-8 M 24-epibrassinolide individually and in combination under 100 uM Cu and Cd in a completely randomized design using four replicates. Whereas 100 uM of Cu and Cd reduced antioxidant activity, photosynthetic capacity, plant tolerance, and ultimately plant growth, the co-application of 100 uM TiO2 NPs and 10E-8 M EBL+ heavy metals (Cu and Cd) resulted in a significant increase in plant antioxidant activity (85%), nonenzymatic antioxidant activities (47%), photosynthetic pigments (43%), fluorescence parameters (68%), plant growth (39%), and plant tolerance (41%) and a significant reduction in the contents of malondialdehyde (45%), hydrogen peroxide (36%), superoxide radical (62%), and soluble protein (28%), as well as the percentage of electrolyte leakage (49%), relative to the control. Moreover, heavy metal accumulation and translocation were reduced by TiO2 NPs and EBL individually and in combination, which could improve bamboo plant tolerance.