Demonstration of a strict molecular oxygen requirement of yellow latex oxidation in the Central Amazon canopy tree Muiratinga (Maquira sclerophylla (Ducke) C.C. Berg)

Resumo

Plant-derived latex is widely used in rubber production and plays important roles in ecological processes in the tropics. Although latex from the commercially important tree Hevea brasiliensis regulates latex oxidation resulting in browning, little is known about latex oxidation in highly diverse tropical ecosystems. Here we show that upon physical trunk damage, yellow latex released from the canopy tree Muiratinga (Maquira sclerophylla (Ducke) C.C. Berg) is rapidly and extensively oxidized to a black resin in the presence of air within 15-30 min. In a nitrogen atmosphere, latex oxidation was inhibited, but was immediately activated upon exposure to air. The results suggest the occurrence of O2-dependent oxidative enzymes including polyphenol oxidase (PPO) within the latex of Muiratinga and supports previous findings of a key role of oxidation during latex coagulation. The findings therefore have important implications for understanding the mechanisms of latex coagulation and its ecological role(s) including wound sealing and defense against herbivores.