Dynamics of Hydrogen Peroxide Accumulation During Tip Growth of Infection Thread in Nodules and Cell Differentiation in Pea (Pisum sativum L.) Symbiotic Nodules

Hydrogen peroxide (H₂O₂) in plants is produced in relatively large amounts and plays a universal role in plant defense and physiological responses, including the regulation of growth and development. In the <i>Rhizobium</i>-legume symbiosis, hydrogen peroxide plays an important signaling role throughout the development of this interaction. In the functioning nodule, H₂O₂ has been shown to be involved in bacterial differentiation into the symbiotic form and in nodule senescence. In this study, the pattern of H₂O₂ accumulation in pea (<i>Pisum sativum</i> L.) wild-type and mutant nodules blocked at different stages of the infection process was analyzed using a cytochemical reaction with cerium chloride. The observed dynamics of H₂O₂ deposition in the infection thread walls indicated that the distribution of H₂O₂ was apparently related to the stiffness of the infection thread wall. The dynamics of H₂O₂ accumulation was traced, and its patterns in different nodule zones were determined in order to investigate the relationship of H₂O₂ localization and distribution with the stages of symbiotic nodule development in <i>P. sativum</i>. The patterns of H₂O₂ localization in different zones of the indeterminate nodule have been partially confirmed by comparative analysis on mutant genotypes.