title: Abscisic acid, xanthoxin and violaxanthin in the caps of gravistimulated maize roots.
abstract: The occurrence and distribution of abscisic acid (ABA), xanthoxin (Xa) and the carotenoid violaxanthin (Va) were investigated in root tips of maize (Zea mays L. cv. Merit).  In roots grown in the dark, Va and ABA were present in relatively high amounts in the root cap and in low amounts in the adjacent terminal 1.5 mm of the root.  Xanthoxin was present in equal concentrations in both regions.  In roots exposed to light, the ABA distribution was reversed, with relatively low levels in the root cap and high levels in the adjacent 1.5-mm segment.  Light also caused a decrease in Va in both regions of the root and an increase in Xa, especially in the cap.  In the maize cultivar used for this work, light is necessary for gravitropic curving.  This response occurs within the same time frame as the light-induced ABA redistribution as well as the changes in the levels of Va and Xa.  These data are consistent with a role for ABA in root gravitropism and support the proposal that Xa may arise from the turnover of Va.
authors.affiliation: Department of Botany, University of California, Berkeley 94720, USA.
authors.forename: L J
authors.initials: LJ
authors.lastname: Feldman
authors.forename: N J
authors.initials: NJ
authors.lastname: Arroyave
authors.forename: P S
authors.initials: PS
authors.lastname: Sun
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D002338:Carotenoids / Q000378:metabolism; D006112:Gravitation; D018522:Gravitropism / Q000502:physiology*; D008027:Light; D010937:Plant Growth Regulators / Q000378:metabolism*; D018518:Plant Root Cap / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism / Q000502:physiology; D012717:Sesquiterpenes / Q000378:metabolism*; D024341:Xanthophylls; D003313:Zea mays / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D019207:beta Carotene / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D010937:Plant Growth Regulators; D012717:Sesquiterpenes; D024341:Xanthophylls; D019207:beta Carotene; C012475:xanthoxin; D002338:Carotenoids; C005613:violaxanthin; D000040:Abscisic Acid