Decisive Enzymes and Prediction Models for the Glutathione Content in Spinach (Spinacia oleracea L.) Exposed to Cadmium

In plants, glutathione (GSH) is crucial for the detoxification and tolerance of heavy metals. However, the change characteristics and decisive enzymes involved in GSH metabolism under heavy metal exposure are still unclear. Based on long-term exposure cultivation of spinach and monitoring of the change trends of enzyme activity and GSH contents in response to Cd stress, these issues were clarified. Spinach goes through three statuses in sequence in response to Cd stress, i.e., perception status (PS), response status (RS) and new stable status. With the increase in Cd concentration, the durations of the PS and RS and the time to reach the peaks in the roots were shorter. However, the durations of the PS and the time to reach the peaks in the leaves were longer. The enzyme activities changed significantly in response to diverse Cd stress in RS. γ-glutamyl transpeptidase was vital to the GSH content in roots. Glutathione synthase was important for the GSH content in leaves. The results of this study provide valuable information to find an efficient way to perform GSH adjustments to fulfill the goal of ensuring food safety.