First Direct Evidence of Pan-African Orogeny Associated with Gondwana Assembly in the Cathaysia Block of Southern China.

Metamorphic zircon from a hornblendite in the South China Block (SCB) yield U-Pb age of 533 ± 7 Ma and Hf model ages from 900 to 1200 Ma. Geochemical and isotopic characteristics indicate that primary magma of the hornblendites was probably derived from an enriched asthenospheric mantle source. This Late Neoproterozoic-Cambrian (Pan-African) metamorphic event provides the first direct evidence that the SCB was an integral part of the Gondwana assembly.

[Allelopathy autotoxicity effects of aquatic extracts from rhizospheric soil on rooting and growth of stem cuttings in Pogostemon cablin].

Objective: To study the allelopathy effects of aquatic extracts from rhizospheric soil on the rooting and growth of stem cutting in Pogostemon cablin, and to reveal its mechanism initially.

Methods: The changes of rhizogenesis characteristics and physic-biochemical during cutting seedlings were observed when using different concentration of aquatic extracts from rhizospheric soil.

Results: Aquatic extracts from rhizospheric soil had significant inhibitory effects on rooting rate, root number, root length, root activity, growth rate of cutting with increasing concentrations of tissue extracts; The chlorophyll content of cutting seedlings were decreased, but content of MDA were increased, and activities of POD, PPO and IAAO in cutting seedlings were affected.