Production of reactive oxygen species in Dalbergia nigra seeds under thermal stress

Seed germination is dependent on abiotic factors, temperature being one of the main ones, whose influence causes seed damage under extreme conditions. The aim of the present study was to investigate the effect of different temperatures during germination of D. nigra seeds and their physiological and biochemical implications. We assessed germination percentage and production of superoxide anion (O-2(-)) and hydrogen peroxide (H2O2) in seeds subjected to temperatures of 5, 15, 25, 35 and 45 degrees C for different periods of time. Hydration is promoted at 45 degrees C and inhibited at 5 degrees C, without germination in either, whereas it is minimal at 15 degrees C and at a maximum level at 25 degrees C. Superoxide production increases at higher temperatures (25 and 35 degrees C) after 72 hours of hydration, coinciding with the beginning of radicle protrusion. Production of hydrogen peroxide decreases at all temperatures, except for 5 degrees C, with values near each other at temperatures of 15, 25, and 35 degrees C, where there was radicle protrusion.