Variation Endogenus and Exogenous of Allelochemical 2,4-dihydroxy-7-metoxy-1,4-benzoxazin-3,(4 H )-one (DIMBOA) in Root Architecture of Maize ( Zea mayz )

The concentrations of hydroxamic acids 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3(4H)-one (DIMBOA), in roots and root exudate of 1- to 6- days-old maize plants were determined by high-performance liquid chromatography (HPLC). The highest concentrations of DIMBOA were found in maize root extracts and exudate when maize roots were 2 weeks old and the maize plant was approximately 15 cm in height. The highest concentrations of DIMBOA equivalents were found in root crown. The distribution of DIMBOA in different root parts (seminal roots, primary root, and crown) was also determined. DIMBOA is concentrated in the cortex of all parts of maize roots determined. The concentrations in com- plete organ of nodal roots were significantly higher than any other parts of maize roots. The results indicate that the distri- bution of DIMBOA is heterogeneous within architecture of the root. Different groups of root show different potential root exudation of DIMBOA. The level of endogenous DIMBOA directly correlates with exogenous levels. The high concentra- tions of these substances in the maize root are may be relevant in the resistance of maize varieties to subterranean pest insects.