Physiological Mechanisms Underlying the Substrate-Dependent Enhancement of Cd Tolerance in Maize by AMF and UPB Co-Inoculation
Year: 2026
Type: preprint
Abstract: Background Arbuscular mycorrhizal fungi (AMF) and urease-producing bacteria (UPB) are common rhizosphere microorganisms in cadmium (Cd)-contaminated soils, but their effects on maize growth and Cd tolerance across substrates remain unclear. Purpose To evaluate the effects of single inoculation with AMF or UPB and dual inoculation (BF) on maize growth, physiology, and Cd tolerance under sand and soil culture, and to clarify the substrate-dependent physiological mechanisms. Methods Sand- and soil-culture experiments under 25 mg kg⁻¹ Cd stress were conducted. The treatments included single inoculation with AMF or UPB and dual inoculation (BF). Maize growth, physiology, and Cd tolerance were evaluated. Results In sand culture, BF increased plant height, shoot and belowground biomass, and stomatal conductance by 47–75%, while AMF increased root length and root surface area by 274% and 100% and reduced shoot Cd content by 57%; BF increased shoot and belowground Cd accumulation by 280% and 77%. In soil culture, UPB increased plant height by 16%, and AMF, UPB, and BF increased shoot biomass by 47–62%. UPB enhanced photosynthetic rate and stomatal conductance by 28% and 51%; BF increased stomatal conductance by 44% and decreased transpiration rate by 27%. AMF increased shoot K and belowground P by 61% and 45% and reduced shoot Cd content by 20%; BF reduced shoot Cd content by 16%; AMF increased belowground Cd accumulation by 31%. Inoculation reduced MDA content, enhanced SOD, POD, and CAT activities, and modulated IAA, ABA, ZR, and GA levels, with AMF and UPB interactions. Partial least squares structural equation modeling (PLS-SEM) indicated that in sand culture, AMF and UPB mainly affected photosynthesis by regulating endogenous hormones, thereby reducing maize Cd content; in soil culture, AMF and UPB treatments exerted direct negative effects on Cd content, whereas the hormonal pathway indirectly reduced Cd content per unit biomass, mainly through photosynthetic improvement and growth dilution. Conclusion Overall, AMF and UPB reduce Cd and enhance maize Cd tolerance via photosynthetic physiology, antioxidant defense, and hormone modulation, with substrate-dependent co-inoculation effects.
Source: Research Square
Institution: Yunnan Agricultural University
Language: English
Subfield: Plant Science
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7225639723