Amaranthus Biochar-Based Microbial Cell Composites for Alleviation of Drought and Cadmium Stress: A Novel Bioremediation Approach

Abstract

Metal contamination coupled with aridity is a major challenge for remediation of abiotic stressed soils throughout the world. Both biochar and beneficial bacteria showed a significant effect in bioremediation; however, their conjugate study needs more exploration. Two rhizobacteria strains Serratia sp. FV34b and Pseudomonas sp. ASe42b isolated from multi-metal and drought stressed sites showed multiple plant-growth-promoting attributes (phosphate solubilization, indole-3-acetic acid, siderophore, and ammonia production). Both strains were able to tolerate a high concentration of Cd along with being resistant to drought (−0.05 to −0.73 MPa). The seldom studied biomass of Amaranthus caudatus L. was used for biochar preparation by pyrolyzing it at 470 °C for 160 min under limited oxygen and then using it for the preparation of biochar-based microbial cell composites (BMC)s. To check the efficiency of BMC under Cd stress (21 mg kg−1 soil) and drought, a pot-scale study was conducted using Brassica napus L. for 47 days. Both the BMC5 (Biochar + Serratia sp. FV43b) and BMC9 (Biochar + Pseudomonas sp. ASe42b) improved the seed germination, plant biometrical (shoot and root biomass, length of organs) and physiological (photosynthetic pigments, proline, malondialdehyde, and relative water content) parameters under drought (exerted until it reaches up to 50% of field capacity) and Cd-spiked soil. However, for most of them, no or few significant differences were observed for BMC9 before and after drought. Moreover, BMC9 maximized the Cd accumulation in root and meager transfer to shoot, making it a best bioformulation for sustainable bioremediation of Cd and drought stressed soils using rapeseed plant.

Combined Application of Biochar and Plant Growth-Promoting Rhizobacteria Improves Heavy Metal and Drought Stress Tolerance in Zea mays

“…However, the accumulation of proline under HM, drought, and HM+drought stress conditions was significantly lower in ARN7- and GS-BC-treated plants compared to their respective control counterparts ( Figure 3 b). Similar observations were previously documented by Anbuganesan et al [ 7 ] and Tripti et al [ 16 ] where they noted reduced proline content upon the application of biochar and PGP bacteria under HM and drought stress conditions and suggested that treatment with biochar and PGP bacteria cumulatively reduced the stress effects caused by HM and drought.…”

“…Recently, bioaugmentation with plant growth-promoting rhizobacteria (PGPR) has also gained great attention as an effective strategy to mitigate various abiotic stresses in plants and improve crop productivity [ 16 , 17 , 18 ]. PGPR with the potential to tolerate abiotic stresses including HM, drought, etc., can colonize the plant rhizosphere and exhibit beneficial effects on plants by synthesizing various plant growth-promoting (PGP) substances such as 1-aminocyclopropane-1-carboxylate deaminase, siderophores, indole-3-acetic acid (IAA), exopolysaccharides, antimicrobial metabolites, N fixation, and solubilizing P, K, Zn, etc.…”

Salicylic acid alleviates the effects of cadmium and drought stress by regulating water status, ions, and antioxidant defense in Pterocarya fraxinifolia

“…Among these factors, soil-associated stressors such as water scarcity and heavy metals may be more detrimental in terms of plant morphological, physiological, and biochemical processes, which could lead to decrement in growth, biomass, and yield. Known as a highly toxic heavy metal, cadmium (Cd) is released into the environment through human activities such as mining, fertilizers, pesticides, and industrial processes (Tripti et al, 2023). Plants easily accumulate Cd from the soil, and excessive Cd uptake leads to metabolic defects and growth inhibition (Zhang et al, 2023a).…”