Photosynthetica 2026, 64(3):245-257 | DOI: 10.32615/ps.2026.034

Exogenous melatonin enhances drought tolerance and secondary-metabolite accumulation in Paeonia ostii 'Fengdan' in association with improved PSI-PSII photochemical coordination

L.X. ZHANG1, †, B. ZHANG1, †, Y.M. SUN2, 3, X.L. ZHAO1, Z. WANG2, 3, Q.M. ZHANG2, 3, K.K. ZHAO1, X.F. LI2, X.G. HOU1, Q.S. CHANG2, 3
1 College of Agriculture, Henan University of Science and Technology, 471000 Luoyang, China
2 College of Horticulture and Plant Protection, Henan University of Science and Technology, 471000 Luoyang, China
3 Henan Key Laboratory of Germplasm Innovation and Utilization of Eco-economic Woody Plant, 471023 Luoyang, China

Drought limits the growth of Paeonia ostii 'Fengdan'. While melatonin (MT) is known to enhance general drought tolerance, its association with Photosystem I-Photosystem II (PSI-PSII) photochemical coordination and secondary-metabolite accumulation in P. ostii remains unclear. We foliar-sprayed potted plants under simulated drought with 0, 50, 100, 200, and 400 μmol(MT) L-1. Drought induced severe oxidative damage, impaired photosynthesis, and disrupted photochemical coordination between PSI and PSII. Among all treatments, 100 μmol(MT) L-1 proved the most effective. It coincided with reduced reactive oxygen species and membrane damage, alongside increased antioxidants, osmolytes, and PSI/PSII performance. Furthermore, compared to drought alone, 100 μmol(MT) L-1 treatment increased the root-bark contents of total flavonoids, total phenolics, gallic acid, catechin, albiflorin, paeoniflorin, benzoic acid, and paeonol by 48.1, 36.1, 17.7, 69.4, 69.9, 24.1, 7.7, and 22.7%, respectively. Thus, 100 μmol(MT) L-1 alleviated drought-induced physiological damage and increased selected secondary-metabolite contents in P. ostii.

Additional key words: antioxidant system; drought stress; melatonin; Paeonia ostii 'Fengdan'; photosynthesis.

Received: July 30, 2026; Revised: September 20, 2026; Accepted: September 22, 2026; Published: October 20, 2026  Show citation

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ZHANG, L.X., ZHANG, B., SUN, Y.M., ZHAO, X.L., WANG, Z., ZHANG, Q.M., ... CHANG, Q.S. (2026). Exogenous melatonin enhances drought tolerance and secondary-metabolite accumulation in Paeonia ostii 'Fengdan' in association with improved PSI-PSII photochemical coordination. Photosynthetica, 64(3), 245-257. doi: 10.32615/ps.2026.034
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