The increasing prevalence of cadmium (Cd)-contaminated agricultural soils threatens the safe production of maize (Zea mays L.). To decrease the Cd accumulation in maize, a pot experiment was conducted to study the effects of humic acid on the growth and Cd uptake of maize seedlings. Cd treatment led to a decrease in biomass and photosynthetic pigment content in maize seedlings, as well as an increase in the activities of antioxidant enzymes. Under Cd stress, the application of humic acid resulted in an increase in biomass, photosynthetic pigment content, and antioxidant enzyme activity in maize seedlings. Additionally, the application of humic acid led to a decrease in root Cd content and an increase in shoot Cd content and translocation factor in maize seedlings under Cd stress. Compared to Cd treatment, humic acid reduced root Cd content by 14.63% and increased shoot Cd content by 12.81%. Furthermore, the carotenoid content, translocation factor, chlorophyll a + b content, and chlorophyll a content were strongly associated with shoot Cd content under Cd stress. Therefore, the application of humic acid can enhance growth, inhibit Cd uptake in roots, and promote Cd translocation from roots to shoots of maize seedlings under Cd stress.
Keywords: Grain crop; heavy metal; physiology; plant biostimulant.
A novel finding of our study is that the application of humic acid can enhance the growth and Cd uptake of maize seedlings under Cd stress. This finding suggests that while humic acid shows promise for improving plant health, its application may need to be reconsidered in Cd-contaminated agricultural areas.