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Plant function and evolutionary biology
RESEARCH ARTICLE (Open Access)

Melatonin improves drought stress tolerance of pepper (Capsicum annuum) plants via upregulating nitrogen metabolism

Cengiz Kaya https://orcid.org/0000-0001-8938-3463 A * and Sergey Shabala https://orcid.org/0000-0003-2345-8981 B C D *
+ Author Affiliations
- Author Affiliations

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

B Tasmanian Institute of Agriculture, University of Tasmania, Hobart, Tas., Australia.

C School of Biological Science, University of Western Australia, Crawley, WA, Australia.

D International Research Centre for Environmental Membrane Biology, Foshan University, Foshan, China.


Handling Editor: Muhammad Waseem

Functional Plant Biology 51, FP23060 https://doi.org/10.1071/FP23060
Submitted: 7 March 2023  Accepted: 13 May 2023  Published: 2 June 2023

© 2024 The Author(s) (or their employer(s)). Published by CSIRO Publishing. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)

Abstract

While ameliorating effects of melatonin (MT) on abiotic stress tolerance in plants are widely reported, the mechanism that underlies this process remains elusive. This work investigated mechanisms by which MT improved drought tolerance in pepper (Capsicum annuum) plants. A foliar spray of 0.1 mM MT treatment was applied to plants grown at 80% and 40% of full field capacity for 3 days. Drought stress caused a significant decrease in plant dry weight, relative water content, leaf water potential, PSII efficiency (Fv/Fm ratio), chlorophyll, soluble protein, leaf and root nitrogen content. Drought increased hydrogen peroxide, malondialdehyde (MDA), nitrate, ammonium, free amino acids, soluble sugars, proline and glycine betaine. Drought also increased peroxidase (POD), glutathione S-transferase (GST) and catalase (CAT) activities, electrolyte leakage (EL) and methylglyoxal (MG). MT pre-treatment reduced oxidative stress and improved nitrogen metabolism by activating various enzymes such as nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthetase (GOGAT) and glutamine dehydrogenase (GDH) activities. It also activated enzymes related to the glyoxalase system (Gly I and Gly II) and decreased NO3, NH4+ and free amino acid content. Our study suggests a cost-effective and sustainable solution to improve crop productivity in water-limited conditions, by enhancing plant growth, photosynthesis and nitrogen content.

Keywords: antioxidants, glyoxalase system, melatonin, nitrogen, nitrogen metabolism, pepper, ROS, water stress.

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