Peng Zhao

Background and aims: Plants encounter various abiotic stress during their growth, making it essential to understand their responses to such challenges. Though function of OsHMA3 in cadmium (Cd) sequestration into rice root vacuoles has been well characterized, little is known about how different OsHMA3 alleles influence plant responses to high Cd exposure. Methods: In this study, we utilized rice cultivars carrying a functional OsHMA3 allele (9311) and a loss-of-function OsHMA3 allele (W4) to investigate their differences in Cd detoxification responses. Morphological, physiological and subcellular changes, as well as Cd species were analyzed. Results: The results indicated that Cd was more extensively transported to shoots in W4 than 9311 as expected. However, W4 exhibited a more pronounced growth inhibition with reductions in shoot and root length, more severe leaf chlorosis with chlorophyll a, b, and carotenoid levels decreased by 31%, 43%, and 45% in W4, respectively, while no significant reductions were observed in 9311. Enhanced cell ultrastructural damage, including membranolytic changes, nuclear membrane lysis, and damage to the nucleus, was noted in W4, while, relatively normal cell structure in 9311. The antioxidant enzyme systems exhibited greater responses in W4 than those in 9311. Additionally, lower levels of nitrate/nitrite, chloride, and aminophenol Cd forms were found in W4 roots, while higher concentrations of these were observed in shoots, indicating distinct Cd detoxicity response between W4 and 9311. Conclusion: This study underscores the significance of the OsHMA3 gene in Cd detoxification responses, offering valuable insights into the mechanisms of plant Cd detoxification.

Cadmium (Cd) contamination in agricultural soils has emerged as a significant concern, particularly due to its potential impact on plant-based food. Soil pH reductions can exacerbate Cd mobility, leading to excessive accumulation in crops. While liming has been demonstrated as an effective method to mitigate Cd accumulation in rice grains in acid soils of southern China, its efficacy in remediating acid soils in northern China remains unclear. In this study, a multi-year field experiment was conducted on farmland impacted by zinc ore smelting at coordinates of 33.92° N 112.46° E to investigate the use of limestone for controlling Cd accumulation in wheat and maize grains. The results indicated that applying 7.5 t ha⁻¹ of limestone significantly raised the soil pH from 4.5 to 6.8 as anticipated. Different rates of limestone application (2.25, 4.45, and 7.50 t ha⁻¹) reduced Cd bioavailability in the soil by 20–54%, and Cd accumulation in wheat grains by 5–38% and maize grains by 21–63%, without yield penalty. The remediation effects were sustained for at least 27 months, highlighting limestone as a promising ameliorant for smelting-affected farmland in northern China.