title: Controls of the quantum yield and saturation light of isoprene emission in different-aged aspen leaves.
abstract: Leaf age alters the balance between the use of end-product of plastidic isoprenoid synthesis pathway, dimethylallyl diphosphate (DMADP), in prenyltransferase reactions leading to synthesis of pigments of photosynthetic machinery and in isoprene synthesis, but the implications of such changes on environmental responses of isoprene emission have not been studied. Because under light-limited conditions, isoprene emission rate is controlled by DMADP pool size (SDMADP ), shifts in the share of different processes are expected to particularly strongly alter the light dependency of isoprene emission. We examined light responses of isoprene emission in young fully expanded, mature and old non-senescent leaves of hybrid aspen (Populus tremula x P. tremuloides) and estimated in vivo SDMADP and isoprene synthase activity from post-illumination isoprene release. Isoprene emission capacity was 1.5-fold larger in mature than in young and old leaves. The initial quantum yield of isoprene emission (αI ) increased by 2.5-fold with increasing leaf age primarily as the result of increasing SDMADP . The saturating light intensity (QI90 ) decreased by 2.3-fold with increasing leaf age, and this mainly reflected limited light-dependent increase of SDMADP possibly due to feedback inhibition by DMADP. These major age-dependent changes in the shape of the light response need consideration in modelling canopy isoprene emission.
authors.affiliation: Estonian University of Life Sciences, 51014, Tartu, Estonia.|Estonian Academy of Sciences, 10130, Tallinn, Estonia.
authors.forename: Ülo
authors.initials: Ü
authors.lastname: Niinemets
authors.affiliation: Estonian University of Life Sciences, 51014, Tartu, Estonia.|Zhejiang A&F University, Hangzhou, 311300, China.
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Sun
authors.affiliation: Estonian University of Life Sciences, 51014, Tartu, Estonia.
authors.forename: Eero
authors.initials: E
authors.lastname: Talts
mesh_terms: D002070:Butadienes; D004777:Environment; D045782:Hemiterpenes / Q000378:metabolism*; D008027:Light; D064688:Metabolic Flux Analysis; D053858:Metabolic Networks and Pathways / Q000528:radiation effects; D009943:Organophosphorus Compounds / Q000378:metabolism*; D010420:Pentanes; D010788:Photosynthesis / Q000528:radiation effects; D018515:Plant Leaves / Q000502:physiology / Q000528:radiation effects; D010940:Plant Proteins / Q000378:metabolism; D018087:Plastids / Q000528:radiation effects; D032107:Populus / Q000502:physiology* / Q000528:radiation effects
chemical_list: D002070:Butadienes; D045782:Hemiterpenes; D009943:Organophosphorus Compounds; D010420:Pentanes; D010940:Plant Proteins; C005059:isoprene; C043060:3,3-dimethylallyl pyrophosphate
keywords: dimethylallyl diphosphate; isoprene synthase; leaf ontogeny; light response curves