Evaluation and physiological response of peony (Paeonia lactiflora Pall.) under salt stress

Herbaceous peony (Paeonia lactiflora Pall.) is widely cultivated in China as a traditional ornamental flower, while soil salinization has negatively affected its cultivation.

In this study, 20 herbaceous peony cultivars were subjected to 400 mM NaCl solution (1 L per pot), applied once every 3 days for a total of 5 applications over 15 days. A non-saline control (0 mM NaCl) was used for phenotypic reference, with higher phenotypic injury scores representing more serious damage. Seven morphological indices were measured before salt treatment, and phenotypic and physiological indices were determined after treatment.

Phenotypic scoring and cluster analysis indicated that three cultivars, namely 'Red Charm', 'Bartzella', 'Sarah Bernhardt', showed the strongest relative salt tolerance under severe stress. Correlation and stepwise regression analyses suggested that leaf thickness and stem diameter could serve as potential preliminary indicators for salt tolerance evaluation, with higher values corresponding to better salt tolerance. Under salt stress, salt-tolerant cultivars exhibited higher antioxidant enzyme activities, as well as significantly lower relative electrolyte leakage and malondialdehyde (MDA) content than salt-sensitive cultivars (P < 0.05). The maximum photochemical efficiency of PSII (Fv/Fm) was highly sensitive to salt stress and decreased significantly with reduced salt tolerance (P < 0.05).

This study provides exploratory evidence for the rapid screening of salt-tolerant germplasm in herbaceous peony using morphological indicators.