NONINDUCED CYCLIC HYDROXAMIC ACIDS IN WHEAT DURING JUVENILE STAGE OF GROWTH

2,4-Dihydroxy-1,4-benzoxazine-3-one glucoside (DIBOA-G) and its methoxy analogue, 2,4-dihydroxy-7-methoxy-1,4-benzoxazine-3-one glucoside (DIMBOA-G), were present in germinating wheat (Triticum aestivum); the corresponding aglycones, DIBOA and DIMBOA, appeared soon after germination. The amounts of these compounds reached a maximum 12-48 hours after germination, and then decreased to undetectable levels as the plants began autotrophic growth. The time of their appearance was little affected by using seeds either sterilized or non-sterilized, by infection with pathogens and wounding with a razor blade. The concentration of DIBOA was found to be 0.2-0.3 nmol mg(-1) fr. wt (0.2-0.3 mM if the density of plant tissue is assumed to be uniform and unity) and that of DIMBOA was 0.7-1.0 nmol mg(-1) (0.7-1.0 mM). The aglycones retarded the germ tube growth of species of fungi at 0.3 mM. These observations suggest that the appearance of benzoxazinones is as defence compounds in the juvenile stage of growth. [C-14]Anthranilic acid was incorporated into DIBOA-G and DIMBOA-G when administered to embryos isolated from pre-emerging seeds, showing that the series of compounds are generated by de novo synthesis.