Effect of exogenous additives on oxidative stress and defense system of a tree: Zanthoxylum armatum DC. under in vitro conditions

Abstract

Toxicity related to oxidative stress has been a concern for mature, woody tree species with high phenolic content when placed under in vitro conditions, particularly at explant establishment stage. The study of biochemical factors responsible for oxidative stress (lipid peroxidation, reactive oxygen species like hydrogen peroxide) and the defense (antioxidant enzymes and non-enzymatic factors) that the plant offers, in the tree system under in vitro environment requires special consideration. This study focuses on the effect of exogenous additives [polyvinyl pyrrolidone (PVP), citric acid (CC), ascorbic acid (AA)] and initial dark treatment on oxidative stress, defense system, DNA oxidation, total chlorophyll content for the in vitro explant establishment of a medicinal tree Zanthoxylum armatum DC., for a duration of 1-month. Exogenous additives and darkness maintained a sustained level of lipid peroxidation hydrogen peroxide, oxidized DNA content and antioxidant enzymes (superoxide dismutase, catalase, and ascorbate peroxidase) in the modified treatment throughout the in vitro experimental period, in comparison to the control. Thus, establishing a relation between exogenous antioxidants and explant oxidative stress-free condition. This can further be utilized to prevent oxidative leaching of explant of mature and woody trees in vitro. Explants of Z. armatum were able to survive under in vitro conditions for 1 month, with low levels of phenolic leaching and oxidative stress, when additives (2 g L−1 PVP, 100 mg L−1 CC, 100 mg L−1 AA) are added in the medium with initial dark treatment for 72 h.