Co-application of melatonin and zeolite boost bamboo tolerance under cadmium by enhancing antioxidant capacity, osmolyte accumulation, plant nutrient availability, and decreasing cadmium absorption

Abstract

Bamboo, a fast-growing and high biomass plant, is one of the income resources of local people in the south and southeast of Asia, known as a food resource with high calories and fiber. However, increased heavy metal contamination cases in bamboo shoots have recently caused concerns. Recently, the role of zeolite and melatonin in the emendation of plant soil and increasing plant growth has been discovered, yet, there is no data on the combined effect of the two on bamboo species. The concurrent interaction in higher plants, particularly, remains elusive. Here, we investigated the role of a combination of zeolite and melatonin in bamboo under cadmium (Cd) stress. In one-year-old bamboo plants (Sasa kongosanensis f. aureo– striatusor), the treatments included a single 150 µM foliar spray of melatonin (Me) and 15 g Zeolite (Ze) kg−1 soil under four concentrations of Cd toxicity (0, 100, 150, and 200 mg L−1). The Cd-induced oxidative stress with overproduction of reactive oxygen species (ROS), lipoperoxidation, and membrane permeability imbalance in bamboo plants reduced biomass and growth. However, melatonin and zeolite alone and together significantly increased plant nutrients in the soil by enhancement of 23% in phosphorous, 23% in nitrogen, 20% in magnesium, 15% in calcium, 10% in potassium as well as 17% increase in relative water content (RWC), 7% in water content (WC), 16% in soluble carbohydrate, 34% in proline, 29% in antioxidant activity, and 26% in non-antioxidants, 13% in ascorbic acid, 24% in anthocyanin, 28% in chlorophylls, 14% in shoot, and 16% in root dry biomass and 15% in shoot length. We concluded that combining 150 µM melatonin and 15 g zeolite with essential mechanisms such as improving antioxidants, increasing plant nutrient availability, reducing Cd absorption, and raising osmolyte accumulation promotes bamboo durability against Cd toxicity and can help further reduce metal toxicity in bamboo species. Such an approach might subsequently have benefits for food safety.