Resumo

GONZALEZ, Juan A.; BUEDO, Sebastián E.  e  PRADO, Fernando E.. Caracterización fotosintética en plantas jóvenes y adultas de Alnus acuminata (“aliso del cerro”) en las Yungas (Tucumán, Argentina). Lilloa [online]. 2017, vol.54, n.1, pp.1-10. ISSN 0075-9481.

Maximum photosynthetic assimilation (A_max) and other gas exchange-related parameters such as stomatal conductance (g_s), leaf transpiration (T_r) and internal CO₂ concentration were studied in both juvenile and mature trees of Alnus acuminata. The carboxilation efficiency (A_max/C_i), intrinsic water-use efficiency (EUAi), leaf nitrogen and photosynthetic pigment contens, specific leaf area (SLA), and specific leaf mass (SLM) were also measured. From assimilation rate vs. photosynthetic active radiation (PAR) curves the light compensation point (LCP), light saturation point (LSP), quantum efficiency (0_CO2), curvature factor 0 and maximum electron transport rate (ETR_max) were determined. Even though light regime at the study site is homogeneous, microhabitats where juvenile and mature alder specimens grow are different. So in forests with mature plants they grow exposed to differential solar radiation due to neighborhood effect between specimens, while juvenile specimens grow more openly without interference and then are more exposed to solar radiation. Results show that in juvenile specimens most of evaluated parameters were higher than in adult ones. From the ecophysiological point of view this study shows that both photosynthetic assimilation and internal structures of A. acuminata leaf vary with the ontogeny; behaving juvenile specimens as "light-demanding" species, and adult specimens as "shadow-tolerant" ones.

Palavras-chave : Alder, photosynthesis, carbon sink, Argentinean northwest, maximum electron transport rate..

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