The allelopathic effects of exogenous pyrogallol on antioxidant metabolism and leaf gas exchange in arsenic-stressed maize (Zea mays L.) seedlings

Abstract

Pyrogallol (PG) is a polyphenol naturally occurring in the leaves and fruits of various plants and is widely utilized as an active component in pharmaceuticals. Although the allelopathic activities of phenolic compounds are well-documented, the allelopathic effects of pyrogallol under heavy metal stress remain poorly understood. This study investigated the effects of PG on oxidative stress indicators, enzymatic and non-enzymatic antioxidant responses, and leaf gas exchange parameters in maize (Zea mays L.) seedlings under arsenic (As) stress. The combined treatment with PG and As led to a significant 5-fold increase in arsenic accumulation compared to treatment with As alone. This application also caused excessive oxidative stress, which exceeded the antioxidant system’s capacity. Although the application of PG or As alone enhanced activity of antioxidant enzymes, their combined application suppressed these enzymes, reducing total antioxidant capacity. Similarly, the combination of PG and As caused a significant decline in photosynthetic performance, further disrupting redox balance and physiological stability. These findings reveal the synergistic toxicity of PG and As, which severely impair plant metabolism. In As-contaminated soils, phenolic compounds like PG may intensify oxidative stress, influencing plant physiology, depending on the concentration. This study underscores the importance of careful management of phenolic compounds in agricultural systems exposed to heavy metal pollution.