Effect of light-irradiation on allelopathic potential of germinating maize

The effect of visible light-irradiation on the allelopathic potential of ge rminating maize (Zea mays) was investigated. Six substances with inhibitory activity were found in the acetone extract of the seedlings, and one subst ance was higher in light-grown seedlings than in dark-grown ones. By spectr al 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 g rowth of roots and hypocotyls of lettuce seedlings. The concentrations of D IBOA in the light-grown maize seedlings and their root exudates were 43 and 0.38 mu mol kg(-1) fr. wt., respectively, and concentrations in the dark-g rown seedlings and their root exudates were 19 and 0.17 mu mol kg(-1) fr. w t., 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 incr ease in the level of DIBOA. (C) 1999 Elsevier Science Ltd. All rights reser ved.