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Plant function and evolutionary biology
RESEARCH ARTICLE

Synergistic mitigation of nickel toxicity in pepper (Capsicum annuum) by nitric oxide and thiourea via regulation of nitrogen metabolism and subcellular nickel distribution

Ferhat Uğurlar https://orcid.org/0000-0002-3663-3497 A and Cengiz Kaya https://orcid.org/0000-0001-8938-3463 A *
+ Author Affiliations
- Author Affiliations

A Soil Science and Plant Nutrition Department, Harran University, Sanliurfa, Turkey.

* Correspondence to: c_kaya70@yahoo.com

Handling Editor: Vadim Demidchik

Functional Plant Biology 50(12) 1099-1116 https://doi.org/10.1071/FP23122
Submitted: 8 June 2023  Accepted: 11 October 2023  Published: 25 October 2023

© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing

Abstract

Nickel (Ni) contamination hinders plant growth and yield. Nitric oxide (NO) and thiourea (Thi) aid plant recovery from heavy metal damage, but their combined effects on pepper (Capsicum annuum) plant tolerance to Ni stress need more study. Sodium nitroprusside (0.1 mM, SNP) and 400 mg L−1 Thi, alone and combined, were studied for their impact on pepper growth under Ni toxicity. Ni stress reduces chlorophyll, PSII efficiency and leaf water and sugar content. However, SNP and Thi alleviate these effects by increasing leaf water, proline and sugar content. It also increased the activities of superoxide dismutase, catalase, ascorbate peroxidase and peroxidase. Nickel stress lowered nitrogen assimilation enzymes (nitrate reductase, nitrite reductase, glutamine synthetase, glutamate synthase and glutamate dehydrogenase) and protein content, but increased nitrate, ammonium and amino acid content. SNP and Thi enhanced nitrogen assimilation, increased protein content and improved pepper plant growth and physiological functions during Ni stress. The combined treatment reduced Ni accumulation, increased Ni in leaf cell walls and potentially in root vacuoles, and decreased Ni concentration in cell organelles. It effectively mitigated Ni toxicity to vital organelles, surpassing the effects of SNP or Thi use alone. This study provides valuable insights for addressing heavy metal contamination in agricultural soils and offers potential strategies for sustainable and eco-friendly farming practices.

Keywords: antioxidant system, nickel toxicity, nitric oxide, nitrogen metabolism, oxidative stress, pepper, subcellular distribution, thiourea.

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