Nickel Toxicity, Altering ROS Scavenging Mechanism and Impairing Sugar Based Signaling in Vigna radiata (L.) Wilczek during Germination and Seedling Establishment

Abstract

Nickel is a heavy metal that has a minor requirement in plants and exerts strong toxic effects at low concentrations. Seed germination and pre-greening stages of seedling establishment represent a brief heterotrophic phase in the life of an otherwise autotrophic organism. Germination is also a stage when the seed relies on stored reserves, including minerals rather than carrying out their uptake and has not been studied. The present work is a study of alteration of germination-related biochemical parameters in the presence of Nickel. Manifestations of Nickel induced oxidative stress as well as antioxidant defenses together with sugar sensing and respiratory enzymatic factors were investigated in seeds of Vigna radiata. Ni treatment increased electron flow through complex IV in cotyledons. It is proposed that inactivation of α-amylase adversely affects sugar movement to the growing seedling, leading to poor sugar sensing by hexokinase. These factors, including possible mis-metallation of electron transport complexes, combine to produce the observed symptoms of Nickel toxicity. The altered antioxidants activity can be correlated with Reactive Oxygen Species production and subsequent changes in seed metabolism.