Variation of community structure and function of rhizospheric denitrifiers at tillering and booting stages of rice

Abstract

We investigated the variation of denitrifying communities in rice rhizosphere at tillering and booting stages in comparison with bulk soils with a pot experiment. The techniques of quantitative polymerase chain reaction (qPCR) and terminal restriction fragment length polymorphism (T-RFLP) were used to measure the abundance and community composition of denitrifiers (narG and nosZ), respectively. The results showed that the potential denitrification activity in the rhizosphere at tillering stage was significantly lower than bulk soils. No significant difference was detected between the rhizosphere and bulk soils at booting stage. The abundance of both narG- and nosZ-containing denitrifying bacteria was significantly higher in rhizosphere than in bulk soils at both tillering and booting stages. In comparison with narG-containing community, community composition and diversity of nosZ-containing bacteria were more sensitive to rice growth. In conclusion, the exudates of rice could induce significantly more denitrifying bacteria in rhizosphere, whose denitrifying activities were related to growth stage of rice. At the period with strong growth, the secretion of roots showed clear restriction to the functions of rhizospheric denitrifiers compared to booting stage.