xanthoxin and norflurazone

Maize seeds were germinated in the dark in the presence of the carotenoid synthesis inhibitor norflurazon and the levels of abscisic acid, xanthoxin and total carotenoids were measured in the root cap and in the adjacent 1.5 mm segment. In norflurazon-treated roots abscisic acid levels were markedly reduced, but an increase occurred in the levels of xanthoxin, a compound structurally and physiologically similar to abscisic acid. In the cultivar of maize (Zea mays L. cv. Merit) used for this work, brief illumination of the root is required for gravitropic curving. Following illumination both control and norflurazon-treated roots showed normal gravitropic curvature; however, the rate of curvature was delayed in norflurazon-treated roots. Our data from norflurazon-treated roots are consistent with a role for xanthoxin in maize root gravitropism. The increase in xanthoxin in the presence of an inhibitor of carotenoid synthesis suggests that xanthoxin and abscisic acid originate, at least in part, via different metabolic pathways.

Topics: Abscisic Acid; Carotenoids; Darkness; Gravitropism; Herbicides; Light; Plant Growth Regulators; Plant Root Cap; Plant Roots; Pyridazines; Sesquiterpenes; Zea mays

Topics: Abscisic Acid; Carotenoids; Cyclohexanecarboxylic Acids; Gravitation; Herbicides; Plants; Pyridazines; Sesquiterpenes; Zea mays