title: Impact of pedospheric and atmospheric sulphur nutrition on sulphur metabolism of Allium cepa L., a species with a potential sink capacity for secondary sulphur compounds.
abstract: Onion (Allium cepa L.) was able to use atmospheric H(2)S as sole sulphur source for growth. The foliarly absorbed H(2)S was rapidly metabolized into water-soluble, non-protein thiol compounds, including cysteine, and subsequently into other sulphur compounds in the shoots. In H(2)S-exposed plants, the accumulation of sulphur compounds in the shoots was nearly linear with the concentration (0.15-0.6 microl l(-1)) and duration of the exposure. Exposure of onion to H(2)S for up to 1 week did not affect the sulphur content of the roots. Secondary sulphur compounds formed a sink for the foliarly absorbed sulphide, and the sulphur accumulation upon H(2)S exposure could, for a great part, be ascribed to enhancement of the content of gamma-glutamyl peptides and/or alliins. Furthermore, there was a substantial increase in the sulphate content in the shoots upon H(2)S exposure. The accumulation of sulphate originated both from the pedosphere and from the oxidation of absorbed atmospheric sulphide, and/or from the degradation of accumulated secondary sulphur compounds. From studies on the interaction between atmospheric and pedospheric sulphur nutrition it was evident that H(2)S exposure did not result in a down-regulation of the sulphate uptake by the roots.
authors.affiliation: Laboratory of Plant Physiology, University of Groningen, PO Box 14, 9750 AA Haren, The Netherlands.
authors.forename: Mark
authors.initials: M
authors.lastname: Durenkamp
authors.forename: Luit J
authors.initials: LJ
authors.lastname: De Kok
mesh_terms: D001272:Atmosphere; D018506:Gene Expression Regulation, Plant; D006862:Hydrogen Sulfide / Q000378:metabolism; D009747:Nutritional Physiological Phenomena; D019697:Onions / Q000254:growth & development / Q000378:metabolism*; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism; D018520:Plant Shoots / Q000254:growth & development / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000032:analysis / Q000378:metabolism; D013455:Sulfur / Q000378:metabolism*; D013997:Time Factors
chemical_list: D013438:Sulfhydryl Compounds; D013455:Sulfur; D006862:Hydrogen Sulfide