Fotoinibição da fotossíntese em mudas de acariquara (minquartia guianensis aubl.,olacaceae) e mogno (swietefiia macrophyfla king,meliaceae),em função do tempo de exposição ã radiação solar na amazônia central

Abstract

Photoinhibition and recovery of photosynthesis was studied in leaves of manwood (Minquarlia guianemis Aubl.) and Mahogany (Swietema macrophylla King) seediings in Central Amazonlan. The piants were accllmated to low llght envíronment beneath canopy of adult trees. Both species showed photolnhibition of photosynthesis measured as a reduction of the Fv/Fm relationship, after 15 minutes of dark adaptation. Fast recovering was observed in manwood seediings exposed to 35 minutes and in mahogany exposed to60 minutes. Slow recovery (after 12 hours ofrecovering) was observed in these treatments tbe exposure to solar radiation longer than 35 minutes (manwood) and 60 minutes in mahogany. Slow recovery reflects damage to Dl protein and inactivation or damage of the PS II. Data collected at the same levei oflight intensity and at different temperature allows us to mfer that the damage to PS II was exacerbated by high temperature. Decreasing on Fv/Fm was negatively associated with the time ofexposure to strong solar radiation. After 2 hours exposure time to high light intensity, in addition to a decrease in the Fv/Fm relationship, a decline in light-satured photosynthesis was aiso observed, which makes evident that these seediings were experiencing photoinhibition. particularly in Manwood.