Effect of light-irradiation on allelopathic potential of germinating maize

Abstract

The effect of visible light-irradiation on the allelopathic potential of germinating maize ( Zea mays) was investigated. Six substances with inhibitory activity were found in the acetone extract of the seedlings, and one substance was higher in light-grown seedlings than in dark-grown ones. By spectral analysis, the substance was identified as 2,4-dihydroxy-1,4-benzoxazin-3-one (DIBOA). At concentrations greater than 0.03 mM, DIBOA inhibited the growth of roots and hypocotyls of lettuce seedlings. The concentrations of DIBOA in the light-grown maize seedlings and their root exudates were 43 and 0.38 μmol kg −1 fr. wt., respectively, and concentrations in the dark-grown seedlings and their root exudates were 19 and 0.17 μmol kg −1 fr. wt., respectively. The level of DIBOA in the dark-grown seedlings increased rapidly upon visible light irradiation. These results suggest that visible light may enhance allelopathic activity of germinating maize due to an increase in the level of DIBOA.