Study On The Plant Allelopathy Of Pogostemon Cablin And Autotoxicity And Mineral Elements Content Of Its Rhizosphere Soil

Pogostemon cablin is a plant of the Lamiaceae family, which is extensively cultivated in the Philippies, Malaysia and Vietnam and other Southeast Asian countries, an important medicinal plants and spices combined. The aerial part of P. cablin has been used for the treatment of the headache, common cold, vomiting, fever, indigestion and diarrhea as well as an antifungal agent in medicinal materials of China and its surrounding countries. P. cablin has good prospects for development. However one major problem is that continuous cropping obstacle phenomenon of P. cablin is serious, which always resulted in a significant reduction in yield and quality, root system underground performance degradation, browning and rot, weak leaf growth, poor plant growth and even death of the whole plant, seriously affected the production of patchouli, sapped the farmers’ emthusiasm in the patchouli growing regions and hindered regional economic development. Thus it is necessary to commence studies on the causes and mechanism of its continuous cropping obstacles. In this paper, patchouli allelopathic effects, mineral element content of seedling and mature P. cablin, autotoxic compounds from rhizosphere soil, mineral element content of rhizosphere soil were studied, by the perspective of patchouli allelopathy and mineral elements, providing a theoretical basis and technical support to achieve effective control of patchouli cropping obstacles.The allelopathy of roots, stems and leaves of P. cablin were studied by use of filter paper dish. The results showed that: the aqueous extracts of root, stem, leaf have different effects on different plants or different parts from same plant, the totally performance was that high concentrations (03.g/ml) showed the strong inhibition and low concentrations (0.0125g/ml) showed no significant effect or no effect, allelopathic effects gradually increased with the incresing concentration of the extract treatment, providing a theoretical basis to achieve effective regulation of patchouli continuous cropping obstacle.Autotoxic substances from patchouli rhizosphere soil were identified by GC-MS method, which malonate(0.161%), myristic acid(0.089%), palmitic acid(0.426%), dibutyl phthalate(1.030%),1,2-benzene dicarboxylic acid, nonyl esters(0.124%), phenylacetic acid(0.893%), heptadecane(0.102%), octadecane(0.282%), nonadecane(0.532%), heneicosane(1.090%), tricosane(2.959%) and pentacosane(3.389%) have been reported as allelopathic autotoxins, which provided evidence for exploring the formation mechanism of patchouli continuous cropping obstacle.Mineral element content of patchouli rhizosphere soil were analyzed by Atomic absorption spectrophotometry, Curcumin colorimetric method, Acetic acid amine exchange flame photometry, the results showed that:the elements proportion imbalances of P. cablin rhizosphere soil associated with continuous cropping obstacles of P. cablin, imbalance proportion of trace elements in rhizosphere soil were much more imbalance, in which Na/Cu, Mn/Cu were57.919%,77.806%of the worst state of balance, which provided a scientific basis to guide the rational fertilization of continuous cropping of P. cablin.