Abstract
The analysis of the effects of cadmium (Cd) on plant cells is crucial to understand defense mechanisms and adaptation strategies of plants against Cd toxicity. In this study, we examined stress-related enzyme activities after one and seven days of Cd application and the ultrastructure of roots of Pisum sativum L. after seven days of Cd treatment (10, 50, 100, and 200 μM CdSO4). Our results showed that phenylalanine ammonia-lyase (PAL) activity and the amount of Cd accumulated in the roots were significantly positively correlated with the Cd concentration used in our experiment. However, Cd caused a decrease of all studied antioxidative enzyme activities (i.e., catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX)). The analysis of the ultrastructure (TEM) showed various responses to Cd, depending on Cd concentrations. In general, lower Cd concentrations (50 and 100 μM CdSO4) mostly resulted in increased amounts of oil bodies, plastolysomes and the accumulation of starch granules in plastids. Meanwhile, roots treated with a higher concentration of Cd (200 μM CdSO4) additionally triggered protective responses such as an increased deposition of suberin lamellae in the endodermal cell walls. This indicates that Cd induces a complex defense response in root tissues.
Highlights
Cadmium (Cd) is a widespread heavy metal, released into the environment mostly by anthropogenic pressure and as a result of the rock mineralization processes [1,2]
We examined the activity of phenylalanine ammonia-lyase (PAL) and three antioxidative enzymes i.e., CAT, ascorbate peroxidase (APX), and guaiacol peroxidase (GPX) after one and seven days of Cd treatment
The present results show that Cd treatment of four-week-old pea plants changes the activity of stress-related enzymes and the ultrastructure of root cells
Summary
Cadmium (Cd) is a widespread heavy metal, released into the environment mostly by anthropogenic pressure (power stations, heating systems, metal-working industries, waste incinerators, urban traffic, cement factories, and as a by-product of phosphate fertilizers) and as a result of the rock mineralization processes [1,2]. The toxic effects of Cd on plants have been studied and described in many review papers [3,4,5,6,7]. Universal or common features involved in plant responses to the Cd application are increased production of toxic oxygen derivatives and alterations of the activity of the antioxidant defense system, which must be proportional to the task of the destruction of reactive oxygen species (ROS) during normal metabolism and during stress [8,9,10,11]. The plant antioxidant defense system includes a variety of antioxidant molecules and enzymes. Changes in the activity of this system can give an inside view of the quantity of stress that plants are under [12].
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