Growth and adaptive changes of rice (Oryza sativa L.) root architecture in response to nitrogen supply

Whole and splitting rootbox system and quartz sand culture were conducted to study the effects of location and level of nitrogen on the allocation of carbohydrate represented by dry matter and parameters of rice root architecture.Results showed that the amount and location of nitrogen supply have affected significantly on allocation of the dry matter between up ground part and under ground one and on parameters of rice root architecture such as root length,root surface area,root volume as well as on root distribution.Biomass of up ground parts of the crop increased with increase of nitrogen fertilization under the condition of whole root supplied nitrogen.Moderate amount of nitrogen fertilization would promote root growth,whereas excessive nitrogen could block root growth.Under condition of half roots supplied with nitrogen,both moderate and high rate of nitrogen would induce root growth and development.Lateral root length,root surface area,root volume were increased by 9% to 91%,20.1% to 87.9% and 32.4% to 88.0% respectively.However,root diameter decreased in the part of nitrogen treatment.The increase of lateral root length,root surface area,root volume could be attributed to the increase of biomass at the moderate nitrogen supply,nevertheless the increase of these parameters was not only related to increase of biomass,but also contributed directly to lateral root length and root surface area per biomass under high rate of nitrogen.It could be concluded that the change of the root length,surface area and volume is one of the adaptive mechanism of rice to nitrogen fertilizer.