title: Day-length effects on carbon stores for respiration of perennial ryegrass.
abstract: • The mechanism controlling the use of stored carbon in respiration is poorly understood. Here, we explore if the reliance on stores as respiratory substrate depends on day length. • Lolium perenne (perennial ryegrass) was grown in continuous light (275 μmol photons m(-2) s(-1) ) or in a 16 : 8 h day : night regime (425 μmol m(-2) s(-1) during the photoperiod), with the same daily photosynthetic photon flux density (PPFD). Plants in stands were labelled with (13)CO(2) : (12)CO(2) for various time intervals. The rates and isotopic signatures of shoot- and root-respired CO(2) were measured after labelling, and water-soluble carbohydrates were determined in biomass. The tracer kinetics in respired CO(2) was analysed with compartmental models to infer the sizes, half-lives and contributions of respiratory substrate pools. • Stores were the main source for respiration in both treatments (c. 60% of all respired carbon). But, continuous light slowed the turnover (+270%) and increased the size (+160%) of the store relative to the 16 : 8 h day : night regime. This effect corresponded with a greatly elevated fructan content. Yet, day length had no effect on sizes and half-lives of other pools serving respiration. • We suggest that the residence time of respiratory carbon was strongly influenced by partitioning of carbon to fructan stores.
authors.affiliation: Department für Pflanzenwissenschaften, Technische Universität München, Freising-Weihenstephan, Germany. lehmeier@wzw.tum.de
authors.forename: Christoph Andreas
authors.initials: CA
authors.lastname: Lehmeier
authors.forename: Fernando Alfredo
authors.initials: FA
authors.lastname: Lattanzi
authors.forename: Ulrike
authors.initials: U
authors.lastname: Gamnitzer
authors.forename: Rudi
authors.initials: R
authors.lastname: Schäufele
authors.forename: Hans
authors.initials: H
authors.lastname: Schnyder
mesh_terms: D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism*; D002247:Carbon Isotopes / Q000378:metabolism; D019069:Cell Respiration / Q000502:physiology*; D005630:Fructans / Q000378:metabolism*; D008129:Lolium / Q000378:metabolism*; D010788:Photosynthesis / Q000502:physiology*; D018517:Plant Roots; D018520:Plant Shoots; D013194:Staining and Labeling; D013472:Sunlight
chemical_list: D002247:Carbon Isotopes; D005630:Fructans; D002245:Carbon Dioxide; D002244:Carbon