Plasticidade e aclimatação foliar à irradiância em espécies da Floresta Atlântica

• Autor(a) principal: Silva, Letícia dos Anjos
• Data de Publicação: 2010
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/362
• topic: Plasticidade fotossintética; Aclimatação luminosa; Floresta Atlântica; Photosynthetic plasticity; Light acclimation; Atlantic Forest; CNPQ::CIENCIAS BIOLOGICAS::BOTANICA

The Atlantic Forest is considered one of the five most endangered ecosystems in world. Therefore, there is a priority for conservation and for development of recovery methodologies of this ecosystem. However, the native cover recovery programs success has been compromised due to the lack of knowledge about species biological behavior. The most pragmatic way to simulate natural regeneration conditions in recovery programs of tropical forests has the foundation on local native species clustering into ecological groups. Ecophysiological studies on the past decades rank tropical wood species in two main ecological groups: the light demanding species group, common to initial succession stages, and the shade tolerant species group, common to late successional stages. It is believed that shade tolerant species should demonstrate low metabolic flexibility to respond to environmental changes, whereas light demanding species would show more plasticity to acclimate more rapidly to changes in light regimes. However, increasing evidences show that both light demanding and shade tolerant species are able to exhibit high photosynthetic plasticity, suggesting that the adjustment flexibility to respond to new environmental conditions are not necessarily related to species successional groups. In regard to this context, this work aimed to evaluate the photosynthetic plasticity and the light acclimation capacity of Atlantic Forest native tropical wood species, belonged to distinct ecological groups, in response to different light environmental conditions. The photosynthetic plasticity was evaluated through photosynthetic apparatus physiological adjustment amplitude and through leaf morphoanatomical adjustments of species submitted to a constant light gradient. The light acclimation capacity was evaluated through photosynthetic apparatus light acclimation capacity and photoinhibition susceptibility, after species transference from a shade condition to a sun exposed condition. The results showed that the photosynthetic plasticity to regulate leaf physiological and morphoanatomical adjustments and the light acclimation capacity, in response to environmental light regimes changes, are not necessarily related to species successional group. Alternatively, results suggest the existence of three ecological groups: two groups of more specialist species and a group of intermediate species. The more specialized species groups are made of pioneer light demanding species, represented by Schinus terebithifolia, and by late shade tolerant species, represented by Lecythis pisonis. The pioneer light demanding species refer to those species which present high photosynthetic capacity, high ability to regulate leaf area, leaf thickness and xylem hydraulic conductance and which present better performance and acclimation capacity under high irradiance environments. The late shade tolerant species refer to those species which present enough photosynthetic efficiency to tolerate environments with low light availability and which present more energetic conservative strategy use of resources and low plasticity to acclimate to high irradiance environments, where they show high susceptibility to photoinhibition. The group of intermediate species, made of most of species and represented in this work by Psedobombax grandiflorum, Joannesia princeps e Hymenaea courbaril, should refer to those species which present plasticity to a variety of characteristics, different degrees of susceptibility to and recovery from photoinhibition and different acclimation capacities to a wide-ranging light radiation spectrum and to colonize both light exposed and low light environments. This hypothesis corroborates to the continuum of ecophysiological responses through light gradient existed in tropical forests. It is expected that the results may help as a support to a better ecophysiological understanding about the biological behavior of the species studied in this work, aiming the management of these species on degraded areas recovery programs of Atlantic Forest ecosystem.