Cyclic hydroxamic acid accumulation in corn seedlings exposed to reduced water potentials before, during, and after germination.

Cyclic hydroxamic acids are innate compounds associated with pest resistance in several grass species. The major cyclic hydroxamic acids of com, 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3-one (DIMBOA) and 2,4-dihydroxy-3H-1,4-benzoxazin-3-one (DIBOA), were measured in seedlings after exposure to various water stress treatments. Both DIMBOA and DIBOA were found in greater quantities in plants experiencing a water deficit stress than in nonstressed plants. The increased cyclic hydroxamic acid coincided with a reduction in seedling growth, suggesting that cyclic hydroxamic acids are stress metabolites. Plants grown under conditions that restrict growth, such as water deficit stress, contain higher cyclic hydroxamic acids, which should make them more resistant to herbivorous pests and pathogenic microorganisms.