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

Abstract

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 µM TiO2 NPs and 10−8 M 24-epibrassinolide individually and in combination under 100 µM Cu and Cd in a completely randomized design using four replicates. Whereas 100 µM of Cu and Cd reduced antioxidant activity, photosynthetic capacity, plant tolerance, and ultimately plant growth, the co-application of 100 µM TiO2 NPs and 10−8 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.

The effects of titanium dioxide (TiO2) nanoparticles on physiological, biochemical, and antioxidant properties of Vitex plant (Vitex agnus - Castus L)

“…Titanium increases photosynthesis in two ways: one by changing the activity of proteins involved in photosynthesis, including fructose-1, 6 bisphosphatase, which affects Calvin cycle, gluconeogenesis enzymes, and changes in the pentose phosphate cycle, which play a role in carbohydrate metabolism. The second is through the increase of chlorophyll, which stimulates and increases photosynthesis [ 46 , 47 ]. TiO2 nanoparticles in rutile form can protect the structure of the chloroplast membrane against the reaction of oxygen free radicals and increase the activity of antioxidant enzyme systems such as POD and CAT [ 17 , 48 ].…”

Nano-enabled agrochemicals: mitigating heavy metal toxicity and enhancing crop adaptability for sustainable crop production

“…Similarly, applying SiNPs to the soil reduced Cd levels in grains, roots, and shoots by 22–82%, 10–60%, and 12–55%, respectively [ 85 ]. TiO 2 -NPs are successful in reducing Cd absorption in several plants, including Coriandrum sativum [ 15 ], bamboo [ 87 ], rice [ 88 ], and summer savory [ 89 ]. The use of CaO-NPs in barley led to a notable reduction in shoot Cd (43–70%) and root (30–40%) of both genotypes [ 11 ].…”

“…Applying Se-NPs in the presence of Cd and other HM stress conditions resulted in a considerable elevation of ASA and GSH in Brassica chinensis [ 131 ]. On the other hand, when bamboo plants were stressed by Cd, TiO 2 -NPs significantly increased levels of non-enzymatic antioxidants such as tocopherols, flavonols, and total phenolics [ 87 ]. The application of ZnO-NP resulted in an elevation of CAT, SOD, and POD activity in Cucumis melo subjected to Cd-induced stress, as well as an augmentation of flavonoids and phenolics [ 132 ].…”

Phytoremediation of Potentially Toxic Elements: Role, Status and Concerns

“…Further, PTEs are also responsible for stomatal closure, increased ethylene production and cause iron deficiency by inhibiting uptake from the medium or due to immobilization in root tissues [ 39 ]. PTEs such as Cd, As, Cr, and Cu inhibit PSII and photosynthetic genes ( psbA and psbB ), and increased accumulation of PTEs in roots, stems and leaves causes reduced growth in plants [ 40 , 41 , 42 ]. Aluminum damages root tips by stimulating the synthesis and accumulation of callose by inhibiting the assembly and release of border cells [ 43 ].Further, Al can accrue in plant cells and have the potential to bind at multiple sites, such as cell wall, cell membrane and nucleic acids, and impede various biological, physiological and cellular processes [ 43 ].…”