Attenuating Effect of an Extract of Cd-Hyperaccumulator Solanum nigrum on the Growth and Physio-chemical Changes of Datura innoxia Under Cd Stress

Abstract

Abstract Purpose The use of plant extracts obtained from plants that are highly tolerant to heavy metal toxicity has been beneficial in improving the growth of plants grown under metal toxicity conditions. A lab experiment was performed to elucidate the alleviating role of foliar applied cadmium (Cd)-hyperaccumulator Solanum nigrum (S. nigrum) extract on Datura innoxia (D. innoxia) plants grown under Cd stress (0, 50, and 100 mg Cd kg-1 soil). Methods Growth parameters, photosynthetic pigment content, osmo-metabolic compounds, reduced glutathione and phytochelatins content, oxidative damage, and lignin content and its related enzyme (cell wall-bound peroxidase, POX) were determined. Results Apart from the foliar application response of S. nigrum leaf extract (SNE) in either Cd exposed or non-Cd exposed plants, growth parameters of D. innoxia plant grown under both Cd concentrations (50 and 100 mg Cd kg-1 soil) in terms of root and shoot fresh, dry weight, length, and leaf area were noticeably diminished by 29 and 51%, 29 and 54%, 35 and 70%, 40 and 53%, 30 and 69%, 40 and 60%, and 11 and 23%, respectively, compared with untreated control plants. Foliar delivered SNE secured the photosynthetic pigment, free amino acids, soluble proteins, and soluble sugar content. Additionally, it lessened the adverse effects of Cd stress on D. innoxia plants by curtailing the content of hydrogen peroxide (H2O2) and malondialdehyde (MDA) by 28 and 27%, and 21 and 23%, respectively, compared with the plants subjected to 50 and 100 mg Cd kg-1 only. The findings herein indicated that the plant water extract and their interactions in the investigated Cd rates significantly augmented phenolics, alkaloids, reduced glutathione and phytochelatins content. Cell wall stiffening in D. innoxia indicated that lignin content and POX were significantly higher in plants exposed to 100 mg Cd kg-1 soil displaying increase values of 275 and 300%, respectively, against non-Cd treated control. The magnitude of increment imposed by Cd stress was lessened by using SNE that reflects on adequate cell growth advocated by limited lignification, in terms of lignin content, and downregulated POX activity. Owing to SNE application, root and leaves Cd contents were efficiently reduced reflecting apparent plant liveliness compared with the SNE non-treated Cd-stressed plants. Conclusions The outcomes of this study designate that foliar application of the Cd-hyperaccumulator S. nigrum leaf extract can be counted as an unconventional and innovative approach in the alleviation of Cd stress and can be employed as integrated practice when Cd-contaminated regions were exploited for sustainable agriculture of the multipurpose plants.