[Book Chapter] Environmental metal cation stress and oxidative burst in plants - A review (original) (raw)

Cation-induced superoxide generation in tobacco cell suspension culture is dependent on ion valence

There have been many reports suggesting the involvement of reactive oxygen species (ROS), including superoxide anion (O2.–), in salt stress. Herein, direct evidence that treatments of cell suspension culture of tobacco (Nicotiana tabacum L.; cell line, BY-2) with various salts of trivalent, divalent and monovalent metals stimulate the immediate production of O2.– is reported. Among the salts tested, LaCl3 and GdCl 3 induced the greatest responses in O2.– production , whereas CaCl2 and MgCl2 showed only moderate effects; salts of monovalent metals such as KCl and NaCl induced much lower responses, indicating that there is a strong relationship between the valence of metals and the level of O2.– production. As the valence of the added metals increased from monovalent to divalent and trivalent, the concentrations required for maximal responses were lowered. Although O2.– production by NaCl and KCl required high concentrations associated with hyperosmolarity, the O2.– generation induced by NaCl and KCl was significantly greater than that induced simply by hyperosmolarity. Since an NADPH oxidase inhibitor, diphenyleneiodonium chloride , showed a strong inhibitory effect on the trivalent and divalent cation-induced generation of O2.– , it is likely that cation treatments activate the O2.–-generating activity of NADPH oxidase.

Published by Metal Stress Responses in Plants: An Overview

Heavy metals are non-biodegradable pollutants which are natural or anthropogenic in origin. It is one of the important abiotic stresses that have the potential to exert undesirable physiological impact on plants leading to reduction in growth and productivity of plants. Metal stress induced oxidative stress in plants. Depending on the duration and type of metal stress experienced by plants, it has evolved detoxification and chelation along with antioxidant system to check ROS generation. This review is an insight to discuss various metal stress responses in plants.

Heavy metal stress and responses in plants

2019

Heavy metals such as Fe, Mn, Cu, Ni, Co, Cd, Zn, Hg and arsenic are for long being accumulated in soils through industrial waste and sewage disposal. Although some of these metals are essential micronutrients responsible for many regular processes in plants, their excess, however, can have detrimental effects and can directly influence the plant growth, metabolism, physiology and senescence. Plants have different mechanisms to fight stress, and they are responsible to maintain homeostasis of essential metals required by plants. These mechanisms also focus on prevention of plants exposure to heavy metals present in the soil or providing tolerance to the plant by detoxifying the metals. Other mechanisms are specific and are initiated when the respective stress is encountered. The first line of defense provided by a plant is to reduce the uptake of metals when stimulated with toxicity of heavy metals and includes the help offered by cellular and root exudates that restricts metals from entering the cell. Many plants have exclusive mechanisms for individual metal ions and are involved in sequestering these ions in compartments avoiding their exposure to sensitive components of the cells. As a second line of defense, other mechanisms for detoxification of these metals are introduced that chelates, transports, sequesters and detoxifies these metal ions in the plant's vacuole. During the time of metal toxicity, oxidative stress is pronounced in the cells and production of stress-related proteins and hormones, antioxidants, signaling molecules including heat-shock proteins synthesis is initiated.