Identification of Autotoxic Compounds in Fibrous Roots of Rehmannia (Rehmannia glutinosa Libosch.)

Rehmannia is a medicinal plant in China. Autotoxicity has been reported to be one of the major problems hindering the consecutive monoculture of Rehmannia. However, potential autotoxins produced by the fibrous roots are less known. In this study, the autotoxicity of these fibrous roots was investigated. Four groups of autotoxic compounds from the aqueous extracts of the fibrous roots were isolated and characterized. The ethyl acetate extracts of these water-soluble compounds were further analyzed and separated into five fractions. Among them, the most autotoxic fraction (Fr 3) was subjected to GC/MS analysis, resulting in 32 identified compounds. Based on literature, nine compounds were selected for testing their autotoxic effects on radicle growth. Seven out of the nine compounds were phenolic, which significantly reduced radicle growth in a concentration-dependent manner. The other two were aliphatic compounds that showed a moderate inhibition effect at three concentrations. Concentration of these compounds in soil samples was determined by HPLC. Furthermore, the autotoxic compounds were also found in the top soil of the commercially cultivated Rehmannia fields. It appears that a close link exists between the autotoxic effects on the seedlings and the compounds extracted from fibrous roots of Rehmannia

A theoretical model on the relation between wind speed and grain size in dust transportation and its paleoclimatic implications

In studies of paleoclimate and paleoenvironment based on loess-palaeosol deposits, the rigorous relations between climate elements and the properties of loessic sediment are scarce because the dynamic processes controlled by the related physical laws are often ignored or arbitrarily simplified. In the current study, the horizontal distance of a suspended dust particle is re-estimated using classical mechanics and the relation between wind speed and the grain size of primary loess is then established. The actual application of this new theoretical relation is given by an example of Duowa profile, western Chinese Loess Plateau. The numerical results imply that the Qaidam Basin could be a likely dust source of the Chinese Loess Plateau.</p

The Impact of Interlayer Electronic Coupling on Charge Transport in Organic Semiconductors: A Case Study on Titanylphthalocyanine Single Crystals

Traditionally, it is believed that three-dimensional transport networks are preferable to those of lower dimensions. We demonstrate that inter-layer electronic couplings may result in a drastic decrease of charge mobilities by utilizing field-effect transistors (FET) based on two phases of titanyl phthalocyanine (TiOPc) crystals. The -phase crystals with electronic couplings along two dimensions show a maximum mobility up to 26.8cm(2)V(-1)s(-1). In sharp contrast, the -phase crystals with extra significant inter-layer electronic couplings show a maximum mobility of only 0.1cm(2)V(-1)s(-1). Theoretical calculations on the bulk crystals and model slabs reveal that the inter-layer electronic couplings for the -phase devices will diminish remarkably the device charge transport abilities owing to the coupling direction perpendicular to the current direction. This work provides new insights into the impact of the dimensionality and directionality of the packing arrangements on charge transport in organic semiconductors