Effects of Rhizosphere Dissolved Oxygen and Nitrogen Form on Root Characteristics and Nitrogen Accumulation of Rice

Dissolved oxygen and N forms have important effects on rice root growth and N availability.Indica hybrid rice Guodao 1 and conventional japonica rice Xiushui 09 were cultured for six weeks in hypoxic nutrient solution with NH4NO3 or(NH4)2SO4 as nitrogen source;Four weeks later,Guodao 1 was transferred to the split-root system at different dissolved oxygen contents(DOTs).The biomass,root morphological traits and nitrogen accumulation were investigated.Under lower rhizosphere oxygen(DOT 0 to 1.0 mg/L),NH4NO3-N significantly increased the plant biomass in comparison with sole NH4+-N,about 69% in Guodao 1 and 41% in Xiushui 09.In addition,the root number,the longest root length,the root dry weight and the root activity for Guodao 1 and Xiushui 09 were also increased under NH4NO3-N nutrition.NH4NO3-N enhanced the N accumulation in roots and shoots of Guodao 1 by 60% and 52%,in roots and shoots of Xiushui 09 by 41% and 33%,respectively.In the split-root system,because of increased rhizosphere oxygen(DOT 8.0 to 9.0 mg/L),the root biomass was increased by 21.6%,the root number by 27%,the longest root length by 14% and the root volume by 10%.The N accumulation in roots was enhanced by 11% under higher rhizosphere oxygen.In conclusion,improvement of dissolved oxygen and ammonium-nitrate N source have positive effect on the root growth and N accumulation of rice plants.