Trocas Gasosas de uma Espécie Lenhosa na Floresta de Transição Amazônia - Cerrado
DOI:
https://doi.org/10.5902/2179460X9367Abstract
As florestas de transição parecem ter um balanço de CO2 nulo, porém as mudanças climáticas que têm ocorrido, como a seca prolongada, podem alterar esse equilíbrio a longo prazo. Desta forma, o presente trabalho teve como objetivo estudar as variáveis fisiológicas: fotossíntese, fotorrespiração e respiração, e entender como essas variáveis podem ser afetadas pelas variações sazonais e a posição da folha na copa da árvore de uma espécie vegetal característica de floresta de transição Amazônia-Cerrado, a Brosimum lactescens S Moore (Moraceae). Utilizando-se um sistema portátil LI-6400 (LI-COR, Inc., Lincoln, NE, USA), as medidas foram realizadas mensalmente. Verificou-se que na estação seca, houve um incremento substancial na densidade de fluxo fotossinteticamente ativo, DFFA, elevando o déficit de pressão de vapor (DPV). Visando reduzir as perdas de água, a planta tende a promover o fechamento dos estômatos, havendo uma diminuição da condutância estomática (gs), reduzindo assim também a concentração de carbono interno (Ci). Como conseqüência, verificou-se que a fotossíntese comportou-se de maneira descendente. Contudo. Nesse contexto, como estratégia para dissipação de energia em excesso, a fotorrespiração (Rp) aumentou e de forma análoga a respiração (Rd) também aumentou. Os resultados encontrados neste estudo sugerem que variações na distribuição da precipitação alteram significativamente as trocas gasosas da espécie estudada.Downloads
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