Allelopathic effects of volatile oil and its two main components from Chenopodium ambrosioides L. on maize (Zea mays) root border cells

Chenopodium ambrosioides L. (family Chenopodiaceae) is native to Central and South America. Introduced C. ambrosioides poses threat to ecosystems in China. To explore allelopathy mechanism, effects of volatile allelochemicals produced by C. ambrosioides on maize root border cells (RBCs) were tested. C. ambrosioides volatile oil and its two main components (alpha-terpinene and cymene), inhibited the maize root growth, changed RBCs number, increased pectin methyl esterase activity and up-regulated rcpmel expression in the maize roots. Volatile oil decreased maize RBCs survival rate to 70.20 % when treated with 5 mu l for 48 h. RBCs nuclei showed abnormalities (fragmentation, marginalization, malformation and dispersion) when treated with volatile oil, alpha-terpinene and cymene. Exposed to volatile oil, nuclear abnormalities rate > 70%, while other treatments were < 27%. There were more vacuoles, chromatin condensation and marginalization in RBCs treated with high doses of volatile oil. TUNEL assay showed death of RBCs was possibly due to programmed cell death or cell necrosis. Thus, the volatile oil, alpha-terpinene and cymene were cytotoxic and genotoxic to RBCs, caused nuclear abnormalities, decreased the RBC viability and induced programmed cell death and necrosis, thereby inhibited the growth of young maize roots. The allelopathic toxicity of oil on the RBCs was significantly greater than either alpha-terpinene or cymene individually.