DISTRIBUTION AND VARIATION OF HYDROXAMIC ACIDS AND RELATED-COMPOUNDS IN MAIZE (ZEA-MAYS) ROOT-SYSTEM

The concentrations of hydroxamic acids and related compounds, 2,4-dihydroxy-7,8-dimethoxy-1,4-benzoxazin-3(4H)-one (DIM2BOA), 2-hydroxy-7,8-dimethoxy-1,4-benzoxazin-3(4H)-one (HMBOA), 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3(4H)-one (DIMBOA), and 6-methoxybenzoxazolinone (MBOA), in roots of 1- to 5-week-old maize plants were determined by high-performance liquid chromatography (HPLC). The highest concentrations of DIM2BOA, HMBOA, and total related compounds were found in maize root extracts 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 4-week-old maize root extracts. The distribution of individual compounds in different tissues (cortex, stele, and complete organ) of various root parts (first set of nodal roots, secondary roots, primary root, mesocotyl, and adventitious roots from mesocotyl) was also determined. Hydroxamic acids and related compounds are concentrated in the cortex of all parts of maize roots determined except mesocotyl. The concentrations of total related compounds and all individual compounds except HMBOA in complete organ of nodal roots were significantly higher than any other parts of maize roots. The high concentrations of these substances in the cortex of maize root may be relevant in the resistance of maize varieties to subterranean pest insects.