Analysis of Glehnia littoralis Fr. allelochemicals in continuously cropped soil and their effects on seedlings growth and physiology of Brassica pekinensis (Lour.).

This work aimed to identify the allelochemicals released by Glehnia littoralis Fr. Schmidt ex Miq. in soil and to study their allelopathic activity on Brassica pekinensis (Lour.) Rupr. In seedling tray assays, the rhizosphere soil from G. littoralis continuous monocropping drastically inhibited the growth of B. pekinensis. In Petri dish assays, Methanolic extracts from control soil (CK), soil under first G. littoralis cropping (FS), and continuous cropping (CS) were tested on germination and seedlings growth of B. pekinensis. These extracts inhibited the germination potential, germination rate, shoot height and root length of Brassica pekinensis. GC-MS analysis of the methanolic extracts revealed the presence of dibutyl phthalate (DBP) and 2,4-Di-tert-butylphenol (2,4-DTBP). These allelochemicals inhibited the seedling growth of B. pekinensis in Petri dish assays, and had deleterious effects on photosynthetic system and redox balance. Activities of peroxidase (POD) and catalase (CAT) increased, whereas, superoxide dismutase (SOD) decreased, chlorophyll content was lowered, but hydrogen peroxide (H2O2) and malondialdehyde (MDA) were increased. Our results suggested that under monocropping G. littoralis releases allelochemicals (DBP and 2,4-DTBP) into the soil. [ABSTRACT FROM AUTHOR]