Heavy Metal Stress in Crop Plants: Toxicity, Tolerance Mechanisms, and Amelioration Strategies

A special issue of Agriculture (ISSN 2077-0472). This special issue belongs to the section "Crop Production".

Deadline for manuscript submissions: closed (25 November 2023) | Viewed by 5304

Special Issue Editors


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Guest Editor
Department of Horticulture and Life Science, Yeungnam University, Gyeongsan 38541, Republic of Korea
Interests: biotic and abiotic stress; physiological, biochemical and molecular analysis; RNS; ROS; melatonin; PGPR; antioxidants; hormones; transcriptomics; proteomics
Department of Horticulture and Life Science, Yeungnam University, Gyeongsan 38541, Republic of Korea
Interests: microbial plant biostimulants; AMF; PGPR; consortia; biotic stress; abiotic stress; physiological and biochemical parameters; ACC deaminase; antioxidant system; gene expression; crop improvement; sustainable agriculture

Special Issue Information

Dear Colleagues,

Heavy metals stress poses a severe threat to the growth and productivity of crops. The transfer of heavy metals from soil to crop plants is of major concern since it may result in bio-magnification across the food chain, resulting in a variety of negative consequences for consumers. In nature, plants are utilizing various mechanisms to combat the adverse effects of heavy metals. Plants respond to heavy metal toxicity by modulating their physiological, biochemical, and molecular status. In response to heavy metal stress, plant induces signals transduction pathways such as reactive oxygen species (ROS), reactive nitrogen species (RNS), hydrogen sulfide, and melatonin to trigger their defense mechanisms. In addition, the defense system of the plants against heavy metal stress could also be improved by the exogenous application of potential chemicals. Moreover, the association between plants and symbiotic microorganisms such as microbial plant biostimulants (MPBs) is a sustainable strategy to augment plant growth and productivity. Several different microorganisms can be used as MPBs to enhance plant growth and produce progressive and reproducible effects on horticultural crops. The present SI will focus on the consequences and mitigation strategies of heavy metal stress-associated damages on crop plants.

Dr. Murtaza Khan
Dr. Sajid Ali
Guest Editors

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Keywords

  • abiotic stress
  • heavy metals
  • antioxidants
  • gene expression
  • physiological and biochemical parameters
  • crop improvement
  • sustainable agriculture
  • food chain
  • PGPR
  • biofertilizer

Published Papers (3 papers)

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Research

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25 pages, 6372 KiB  
Article
Morphological and Structural Responses of Albizia lebbeck to Different Lead and Nickel Stress Levels
by Mahak Naveed, Maria Ghaffar, Zafran Khan, Nimra Gul, Iram Ijaz, Amir Bibi, Soha Pervaiz, Hesham F. Alharby, Muhammad Sayyam Tariq, Syed Riaz Ahmed, Khalid Rehman Hakeem and Daniel K. Y. Tan
Agriculture 2023, 13(7), 1302; https://doi.org/10.3390/agriculture13071302 - 26 Jun 2023
Cited by 1 | Viewed by 1422
Abstract
Lead (Pb) and nickel (Ni) are serious soil pollutants that adversely affect plant growth and development and need to be removed through phytoremediation. The present study aimed to assess the morphological indices of Albizia lebbeck (L.) (Benth.) in relation to anatomical modifications for [...] Read more.
Lead (Pb) and nickel (Ni) are serious soil pollutants that adversely affect plant growth and development and need to be removed through phytoremediation. The present study aimed to assess the morphological indices of Albizia lebbeck (L.) (Benth.) in relation to anatomical modifications for survival under both Pb and Ni stress. The seedlings of A. lebbeck were established and then subjected to four different concentrations, viz. 0 mM, 25 mM, 50 mM and 75 mM, of Pb and Ni for 14 days in two phases. Morphological traits such as shoot length (70.93%), fresh weight (79.27%), dry weight (83.9%), number of root hairs (65.7%), number of leaves per plant (67.4%) and number of leaflets per plant greatly reduced under Pb or Ni stress. Surprisingly, root length increased rather than decreased with the increase in Pb or Ni concentrations, along with an increase in leaflet width, leaflet length and leaflet area. Moreover, root cortical cell area, metaxylem area and phloem area decreased at 75 mM of Pb and Ni while epidermal thickness and cell area increased. Stem epidermal thickness, cell area and phloem area significantly decreased with the consistent increase in metaxylem area and cortical region thickness under both Pb and Ni stress. Leaf anatomical traits such as midrib thickness, abaxial epidermal thickness and stomatal density and adaxial epidermal thickness and stomatal area significantly increased with increasing Pb or Ni stress. Correlation analysis revealed close relations among morphological and anatomical traits (such as root length with cortical region thickness) for better plant survival under Pb or Ni stress, and a PCA-biplot further verified these correlation analyses. Cluster analyses demonstrated the associations among the morphological and anatomical traits based on different stress levels. Furthermore, we found that the longer exposure (from phase 1 to phase 2) of heavy metals stress is more dangerous for plant survival and can ultimately lead to plant death. Moreover, our results also confirmed that Ni is more harmful or dangerous to plants than Pb at high and moderate concentrations. The anatomical modifications ensured the survival of A. lebbeck in extreme heavy metals stress and therefore unlocked its potential to be used as a natural source of phytoremediation. We also recommend that the genetic potential of A. lebbeck associated with its survival under heavy metal stress be investigated. Full article
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16 pages, 1809 KiB  
Article
Physiological and Ultrastructural Changes in Dendranthema morifolium Cultivars Exposed to Different Cadmium Stress Conditions
by Luqman Muhammad, Salahuddin, Asif Khan, Yunwei Zhou, Miao He, Abdulwahed Fahad Alrefaei, Murtaza Khan and Sajid Ali
Agriculture 2023, 13(2), 317; https://doi.org/10.3390/agriculture13020317 - 28 Jan 2023
Cited by 3 | Viewed by 1754
Abstract
Ornamental plant species may vary substantially in their tolerance response to heavy metals. The aim of this research was to check chrysanthemum cultivars, namely Donglin Ruixue (C), Yellow (F), Red pocket (G), and New 9714 (I), which are commonly used as landscape plants [...] Read more.
Ornamental plant species may vary substantially in their tolerance response to heavy metals. The aim of this research was to check chrysanthemum cultivars, namely Donglin Ruixue (C), Yellow (F), Red pocket (G), and New 9714 (I), which are commonly used as landscape plants to determine their levels of cadmium (Cd) tolerance at different cadmium concentrations through hydroponic cultures. Chrysanthemum cultivars were treated with five different Cd concentrations (0, 10, 20, 50, and 100 mg L−1) and different physiological, enzymatic, and ultra-structure traits were taken under consideration in vitro. The results showed that cadmium concentration significantly inhibited the total chlorophyll content, chlorophyll a, chlorophyll b, and carotenoid content. Chlorophyll contents were significantly reduced at higher Cd concentrations in all cultivars, but the reduction rates were higher in cultivar F (59.49%), G (40.41%), I (44.97%), and C (33.86%). Similarly, the chlorophyll b reduction was higher than that of chlorophyll a in I (73.33%), followed by G (58.06%), F (61.66%), and C (32.43%), under Cd stress conditions. Additionally, the relative conductivity was recorded in cultivars C (146.48%), F (223.66%), G (165.96%), and I (154.92%), respectively, at 100 mg L−1 Cd concentrations. Likewise, MDA was significantly increased with high Cd stress, at 155.56, 325.27, 173.91, and 322.18%, in C, F, G, and I cultivars at 100 mg L−1, but it was promoted with a greater increase in F and I cultivars. Similarly, SOD and CAT activities were increased with the increase in Cd stress, but reduced in F and I cultivars at higher stress levels of 100 mg L−1. In the same way, POD activity was significantly higher in the C and G cultivars. Additionally, ultrastructure changes also occurred with the increase in the Cd stress, i.e., 20 mg L−1 to 100 mg L−1, and these changes caused alterations in cell organelles, including in the chloroplast, grana, lamella, thylakoid, and stroma. They also caused noticeable damage to mitochondria at higher Cd concentrations. It was concluded that the higher levels of antioxidative defense of the C and G cultivars of chrysanthemum indicated their ability to tolerate high Cd stress conditions. These could, therefore, be used for their phytoremediation potential in Cd-contaminated areas. Full article
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Review

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14 pages, 1431 KiB  
Review
Research Progress in Soybean by Phytohormone Modulation and Metal Chelation over the Past Decade
by Shifa Shaffique, Sang-Mo Kang, Md. Injamum Ul Hoque, Muhamad Imran, Muhamad Aaqil khan and In-Jung Lee
Agriculture 2023, 13(7), 1325; https://doi.org/10.3390/agriculture13071325 - 28 Jun 2023
Cited by 4 | Viewed by 1467
Abstract
Phytohormones have been acknowledged as an eco-friendly and alternative source for plant growth promotion and abiotic stress tolerance. Heavy metal stress has attained considerable attention worldwide because of its serious effects. Globally, it is a major cause of crop yield loss. Soybean is [...] Read more.
Phytohormones have been acknowledged as an eco-friendly and alternative source for plant growth promotion and abiotic stress tolerance. Heavy metal stress has attained considerable attention worldwide because of its serious effects. Globally, it is a major cause of crop yield loss. Soybean is an important legume crop that continuously faces environmental stress, such as heavy metal stress. The application of plant growth regulators, such as phytohormones, enhances plant tolerance toward heavy metals. Phytohormones augment the interaction with plants. They improve plant productivity under stress due to the potential of phytostabilization. They are capable of enhancing metal stress tolerance by reducing oxidation stress. In the present review, an attempt has been made to summarize the role of phytohormones in metal chelation in a model plant, soybean. The results suggest that among the phytohormones, ABA, JA, SA ET, GA, and IAA are synergistic with metal chelation, whereas cytokinins are antagonistic. The application of phytohormones and corresponding microbes enhances the production of glutathione (GSH), which enhances metal tolerance by metal sequestration. Full article
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