Favorable subcellular distribution, stable binding form and synergistic antioxidation restrict Cd accumulation in the medicinal part of Asparagus cochinchinensis

Abstract

Background and aims

Soil cadmium (Cd) pollution threatens the safe consumption of medicinal materials (Asparagus cochinchinensis). However, related research on the physiological response and medicinal quality of plants under Cd exposure is insufficient.

Methods

This study preliminarily revealed the Cd uptake characteristics and detoxification mechanism of A. cochinchinensis by analyzing the distribution and morphological changes in Cd and explored the response of enzymes and nonenzymes (medicinal components).

Results

As the degree of Cd stress increased, the biomass of different tissues increased under Cd0.5. Mineral elements were absorbed synergistically with Cd in the roots under Cd0.5 (0.91 mg/kg), which counteracted the growth toxicity caused by Cd absorption. In addition, Cd significantly increased in the cell sap to protect organelles, protein and pectic acid (F_NaCl) increased to chelate Cd and maintain a low level of water-soluble Cd (F_W) to reduce its toxicity, and synergistic antioxidation by enzymes and nonenzymes (SOD–CAT–saponins) increased to alleviate damage. In contrast, a high level of Cd stress inhibited the absorption of Mn in tubers and aboveground parts and led to the accumulation of numerous toxic forms of Cd (F_W) in organelles under Cd2 (3.68 mg/kg), potentially affecting photosynthesis and decreasing biomass.

Conclusion

A. cochinchinensis has an adaptive detoxification mechanism to maintain low toxicity; in particular, adjusting the subcellular distribution and morphological changes in Cd increase the resistance of medicinal components, thus maintaining safe growth.