Open Access

ARTICLE

Melatonin Priming Enhances Potassium Dichromate Stress Tolerance and Morpho-Physiological Performance via Genetic Modulation in Melon (Cucumis melo L.) Plant

Tai Liu^1,#, Huichun Xu^1,#, Sikandar Amanullah^2,*, Ye Che¹, Ling Zhang¹, Zeyu Jiang¹, Weiyi Bi¹, Lei Zhu¹, Di Wang^1,*
1 Institute of Horticultural Science, Daqing Branch of Heilongjiang Academy of Agricultural Sciences, Daqing, 163711, China
2 Mountain Horticultural Crops Research and Extension Center, Department of Horticultural Science, North Carolina State University, 455 Research Drive, Mills River, NC 28759, USA
* Corresponding Author: Sikandar Amanullah. Email: ; Di Wang. Email:
# Tai Liu and Huichun Xu contributed equally as co-first authors to this work
(This article belongs to the Special Issue: Recent Research Trends in Genetics, Genomics, and Physiology of Crop Plants–Volume II)

Phyton-International Journal of Experimental Botany https://doi.org/10.32604/phyton.2025.074131

Received 03 October 2025; Accepted 11 December 2025; Published online 12 December 2025

Abstract

Heavy metal accumulation in agricultural soil is primarily driven by pesticides, polluted water, and industrial gas emissions, which pose threats to sustainable crop production. Chromium (Cr) stress has an adverse impact on plant development and metabolism, but approaches to reduce its toxicity and enhance plant resistance remain limited. Melatonin is a potent antioxidant involved in regulating various morpho-physiological functions of plants under different abiotic stresses. In this study, we investigated the impact of exogenous melatonin to mitigate the negative effects of potassium dichromate (PD) stress in melon plants and analyzed genetic modulation of morphological, physiological, and biochemical parameters. The obtained results revealed that melatonin treatment (100 µmol L⁻¹) considerably improved seed germination rate, promoted plant growth, and stabilized chloroplast ultrastructure of leaves under PD-stress. This physiological resilience was similarly reflected by maintained photosynthetic efficiency and significantly stabilized photochemical parameters (e.g., Fv/Fm and NPQ). At the molecular level, quantitative polymerase chain reaction (qPCR) analysis confirmed that melatonin treatment maintained organelle integrity by upregulating primary metabolism indices and hindering Cr accumulation. Specifically, melatonin reduced the Cr-induced downregulation of chlorophyll biosynthesis genes [CmHEMA (MELO3C006296.2), CmGOGAT (MELO3C008481.2), and CmPOR (MELO3C016714.2)], restoring chlorophyll content by up to 5.08 mg·g⁻¹, increased by 67.11%. The expression level of genes [CmSPS (MELO3C003715.2), CmPEPC (MELO3C018724.2), and CmRubisco (MELO3C012180.2)] showed an effective upsurge in carbohydrate synthesis. Moreover, melatonin significantly enhanced the antioxidant system [e.g., increasing SOD (46.13%), POD (35.85%), and APX (25.00%) activities] and promoted the accumulation of lignin and metallothionein [via upregulation of Cm4CL (MELO3C002346.2) and CmMet (MELO3C016513.2) genes], which restricted Cr translocation from the root to the shoot. To summarize, exogenous melatonin application could serve as an effective strategy for mitigating Cr-induced stress in melon by stabilizing basic photosynthetic processes and secondary metabolism through biochemical and molecular defensive mechanisms, thereby preventing Cr translocation by activating the accumulation of secondary metabolites (e.g., lignin and metallothionein) and photo-respiration elements. Our findings provided new perspective to understand melatonin as a viable, multidimensional bio-regulator for improving crop resilience in Cr-polluted agricultural systems.

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Keywords

Cucumis melo; growth indices; heavy metal; melatonin; stress; toxicity

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