Extracellular production of reactive oxygen species during seed germination and early seedling growth in Pisum sativum

摘要

Extracellularly produced reactive oxygen species (ROS) play key roles in plant development, but their significance for seed germination and seedling establishment is poorly understood. Here we report on the characteristics of extracellular ROS production during seed germination and early seedling development in Pisum sativum. Extracellular superoxide (O-2(center dot-)) and hydrogen peroxide (H2O2) production and the activity of extracellular peroxidases (ECPOX) were determined spectrophotometrically, and O-2(center dot-) was identified by electron paramagnetic resonance. Cell wall fractionation of cotyledons, seed coats and radicles was used in conjunction with polyacrylamide gel electrophoresis to investigate substrate specificity and molecular masses of O-2(center dot-)-producing enzymes, and the forces that bind them to the cell wall. Seed imbibition was accompanied by an immediate, transient burst of redox activity that involved O-2(center dot-) and other substances capable of oxidizing epinephrine, and also H2O2. At the final stages of germination, coinciding with radicle elongation, a second increase in O-2(center dot-) but not H2O2 production occurred and was correlated with an increase in extracellular ECPOX activity. Electrophoretic analyses of cell wall fractions demonstrated the presence of enzymes capable of O-2(center dot-) production. The significance of extracellular ROS production during seed germination and early seedling development, and also during seed aging, is discussed. (C) 2010 Elsevier GmbH. All rights reserved.