Hormetic effects of zinc on growth and antioxidant defense system of wheat plants.

Sci Total Environ

College of Resources and Environment, Henan Agricultural University, Zhengzhou 450002, PR China. Electronic address:

Published: February 2022

AI Article Synopsis

  • The study investigates the effects of varying zinc (Zn) concentrations on two wheat varieties, focusing on morphological and physiological responses over 14 days.
  • At lower concentrations (10-100 μM), Zn promotes growth by enhancing photosynthesis and antioxidant enzyme activities, while higher Zn levels (300-1000 μM) result in detrimental effects, such as reduced shoot growth and increased membrane injuries due to oxidization.
  • The research highlights the importance of the AsA-GSH cycle and the accumulation of specific antioxidants in wheat's defense against Zn toxicity, providing insights for improving crop resilience in changing environmental conditions.

Article Abstract

Although hormesis induced by heavy metals is a well-known phenomenon, the involved biological mechanisms are not fully understood. Zinc (Zn) is an essential micronutrient for wheat, an important crop contributing to food security as a main staple food; however, excessive Zn is detrimental to the growth of wheat. The aim of this study was to evaluate morphological and physiological responses of two wheat varieties exposed to a broad range of Zn concentrations (0-1000 μM) for 14 days. Hormesis was induced by Zn in both wheat varieties. Treatment with 10-100 μM Zn promoted biomass accumulation by enhancing the photosynthetic ability, the chlorophyll content and the activities of antioxidant enzymes. Increased root/shoot ratio suggested that shoot growth was severely inhibited when Zn concentration exceeded 300 μM by reducing photosynthetic ability and the content of photosynthetic pigments. Excessive Zn accumulation (Zn treatment of 300-1000 μM) in leaf and root induced membrane injuries through lipid peroxidation as malondialdehyde (MDA) content increased with increasing Zn concentration. The results show that MDA content was higher than other treatments by 16.1-151.1% and 15.0-88.3% (XN979) and 36.8-235.7% and 20.6-83.8% (BN207) in the leaves and roots under 1000 μM Zn treatment. To defend against Zn toxicity, ascorbate (AsA), glutathione (GSH), non-protein thiols (NPT) and phytochelatin (PC) content of both wheat varieties (except leaf GSH content of BN207) was increased, while, the activities of superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, and the content of soluble protein decreased by 300-1000 μM Zn. The results showed that AsA-GSH cycle and NPT and PC content of wheat seedlings play important roles in defending against Zn toxicity. This study contributes new insights into the physiological mechanisms underlying the hormetic response of wheat to Zn, which could be beneficial for optimizing plant health in changing environments and improving risk assessments.

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http://dx.doi.org/10.1016/j.scitotenv.2021.150992DOI Listing

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