title: Characterization of the photosynthetic apparatus in cortical bark chlorenchyma of Scots pine.
abstract: Winter-induced inhibition of photosynthesis in Scots pine (Pinus sylvestris L.) needles is accompanied by a 65% reduction of the maximum photochemical efficiency of photosystem II (PSII), measured as Fv/Fm, but relatively stable photosystem I (PSI) activity. In contrast, the photochemical efficiency of PSII in bark chlorenchyma of Scots pine twigs was shown to be well preserved, while PSI capacity was severely decreased. Low-temperature (77 K) chlorophyll fluorescence measurements also revealed lower relative fluorescence intensity emitted from PSI in bark chlorenchyma compared to needles regardless of the growing season. Nondenaturating SDS-PAGE analysis of the chlorophyll-protein complexes also revealed much lower abundance of LHCI and the CPI band related to light harvesting and the core complex of PSI, respectively, in bark chlorenchyma. These changes were associated with a 38% reduction in the total amount of chlorophyll in the bark chlorenchyma relative to winter needles, but the Chl a/b ratio and carotenoid composition were similar in the two tissues. As distinct from winter pine needles exhibiting ATP/ADP ratio of 11.3, the total adenylate content in winter bark chlorenchyma was 2.5-fold higher and the estimated ATP/ADP ratio was 20.7. The photochemical efficiency of PSII in needles attached to the twig recovered significantly faster (28-30 h) then in detached needles. Fluorescence quenching analysis revealed a high reduction state of Q(A) and the PQ-pool in the green bark tissue. The role of bark chlorenchyma and its photochemical performance during the recovery of photosynthesis from winter stress in Scots pine is discussed.
authors.affiliation: Department of Biology and the Biotron, University of Western Ontario, 1151 Richmond Str. N, London, ON, Canada N6A 5B7.
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Ivanov
authors.forename: Marianna
authors.initials: M
authors.lastname: Krol
authors.forename: Dimitri
authors.initials: D
authors.lastname: Sveshnikov
authors.forename: Gunilla
authors.initials: G
authors.lastname: Malmberg
authors.forename: Per
authors.initials: P
authors.lastname: Gardeström
authors.forename: Vaughan
authors.initials: V
authors.lastname: Hurry
authors.forename: Gunnar
authors.initials: G
authors.lastname: Oquist
authors.forename: Norman P A
authors.initials: NP
authors.lastname: Huner
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism / Q000502:physiology; D002851:Chromatography, High Pressure Liquid; D005453:Fluorescence; D008291:Malate Dehydrogenase / Q000378:metabolism; D010084:Oxidation-Reduction; D010455:Peptides / Q000378:metabolism; D010730:Phosphoenolpyruvate Carboxylase / Q000378:metabolism; D010788:Photosynthesis / Q000502:physiology*; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000502:physiology; D010860:Pigments, Biological / Q000032:analysis; D041605:Pinus sylvestris / Q000033:anatomy & histology / Q000378:metabolism* / Q000502:physiology; D024301:Plant Bark / Q000033:anatomy & histology / Q000378:metabolism* / Q000502:physiology; D012621:Seasons; D013696:Temperature
chemical_list: D010455:Peptides; D045332:Photosystem II Protein Complex; D010860:Pigments, Biological; D002734:Chlorophyll; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D008291:Malate Dehydrogenase; C046446:malate dehydrogenase-(oxaloacetate-decarboxylating) (NAD+); C031917:malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+); D010730:Phosphoenolpyruvate Carboxylase