Impact of repeated freeze-thaw cycles environment on the allelopathic effect to Secale cereale L. seedlings

Allelopathy, as environmental stress, plays a prominent role in stress ecotoxicity, and global warming directly increases freeze-thaw cycles (FTCs) frequency in the winter. Yet, the effect between FTCs environment and allelopathy stress is rarely known, and the interaction of allelopathy stresses lacks consideration. Here, we addressed interactions between artemisinin stress (AS) and A. trifida extract stress (AES) under Non-FTCs and FTCs environments. The results found that AS and AES had an antagonistic relation under Non-FTCs environment, while a strong synergism and cooperation under FTCs environment affect the growth and physiology in S. cereale seedlings. Besides, AS and AES under FTCs environment had more inhibition on the growth of roots and shoots, chlorophylls, photosynthetic parameters, and relative water content; while more promotion on malondialdehyde, soluble sugar, and soluble protein. Moreover, the antioxidant enzyme activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) were increased by AS and AES, showing a good resistance of S. cereale seedlings to allelopathy stress, but FTCs environment significantly weakened this resistance. Thus, the allelopathic effect of AS and AES on S. cereale seedlings was significantly emphasized by FTCs environment.