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1.
Plant Biol (Stuttg) ; 14(1): 88-99, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21972867

RESUMO

Acclimation of foliage photosynthetic properties occurs with varying time kinetics, but structural, chemical and physiological factors controlling the kinetics of acclimation are poorly understood, especially in field environments. We measured chlorophyll fluorescence characteristics, leaf total carotenoid (Car), chlorophyll (Chl) and nitrogen (N) content and leaf dry mass per area (LMA) along vertical light gradients in natural canopies of the herb species, Inula salicina and Centaurea jacea, and tree species, Populus tremula and Tilia cordata, in the middle of the growing season. Presence of stress was assessed on the basis of night measurements of chlorophyll fluorescence. Our aim was to compare the light acclimation of leaf traits, which respond to light availability at long (LMA and N), medium (Chl a/b ratio, Car/Chl ratio) and short time scales (fluorescence characteristics). We found that light acclimation of nitrogen content per unit leaf area (N(area)), chlorophyll content per unit dry mass (Chl(mass)) and Chl/N ratio were related to modifications in LMA. The maximum PSII quantum yield (F(v) /F(m)) increased with increasing growth irradiance in I. salicina and P. tremula but decreased in T. cordata. Leaf growth irradiance, N content and plant species explained the majority of variability in chlorophyll fluorescence characteristics, up to 90% for steady-state fluorescence yield, while the contribution of leaf total carotenoid content was generally not significant. Chlorophyll fluorescence characteristics did not differ strongly between growth forms, but differed among species within a given growth form. These data highlight that foliage acclimation to light is driven by interactions between traits with varying time kinetics.


Assuntos
Carotenoides/metabolismo , Clorofila/metabolismo , Populus/metabolismo , Tilia/metabolismo , Árvores/metabolismo , Aclimatação , Centaurea/metabolismo , Estônia , Fluorescência , Inula/metabolismo , Nitrogênio/metabolismo , Fotossíntese , Folhas de Planta/química , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/metabolismo
2.
Plant Biol (Stuttg) ; 14(2): 306-14, 2012 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-21974690

RESUMO

Needle morphological, chemical and physiological characteristics of Norway spruce were studied in a forest chronosequence in Järvselja Experimental Forest, Estonia. Current-year shoots were sampled from upper canopy positions in five stands, ranging in height from 1.8 to 33.0 m (corresponding age range was 10-85 years). A/C(i) curves were determined to obtain maximum carboxylation rates (V(cmax)) and maximum rates of electron transport (J(max)). Needle nitrogen (N) partitioning into photosynthetic functions was calculated from the values of V(cmax), J(max) and leaf chlorophyll concentration. All needle size parameters (length, width, thickness, volume and cross-sectional areas of mesophyll and xylem) increased significantly with tree height. The needles of taller trees had lower mass-based N and chlorophyll concentrations (21% and 43% difference between shortest and tallest stands, respectively), but higher dry mass per area (35%), dry mass per volume (18%), number of cells per mesophyll cross-section area (40%) and partitioning of N into non-photosynthetic functions (12%). Light saturated net assimilation rate, V(cmax), J(max) and stomatal conductance decreased with tree age (35%, 16%, 12% and 29% difference, respectively). A path analysis model describing tree age-related reduction of photosynthetic capacity as a result of sink limitation provided the best fit to our data. However, since the path model corresponding to source limitation, where photosynthetic reduction derives from changes in needle structure and chemistry was not rejected, we conclude that the decline in photosynthesis with tree age results from several mechanisms (limited sink strength, stomatal and N limitation) operating simultaneously and sequentially.


Assuntos
Fotossíntese/fisiologia , Picea/anatomia & histologia , Picea/fisiologia , Folhas de Planta/anatomia & histologia , Biomassa , Clorofila/metabolismo , Transporte de Elétrons/fisiologia , Luz , Nitrogênio/metabolismo , Picea/crescimento & desenvolvimento , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/fisiologia , Brotos de Planta/anatomia & histologia , Brotos de Planta/crescimento & desenvolvimento , Brotos de Planta/fisiologia , Estômatos de Plantas/fisiologia , Transpiração Vegetal/fisiologia , Distribuição Aleatória , Fatores de Tempo , Árvores/anatomia & histologia , Árvores/crescimento & desenvolvimento , Árvores/fisiologia
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