The key stage of infection is the transfer of bacteria from the infection thread to
the cytoplasm of the nodule cell. This process occurs through endocytosis. The
individual bacteria are surrounded by a membrane of plant origin, within which they
further differentiate into N 2 -fixing bacteroids [63, 65, 69, 71]. The root cells rapidly
replicate, then stop the division, and begin to increase in size, forming a nodule
tissue [7, 70]. After the bacterial invasion in nodules, vascular-fibrous bundles
from the procambium of the central cylinder and then the leading elements of the
Fig. 1 Development of legume-rhizobium symbiosis. Scheme describes the formation of indeterminate nodules
Fig. 2 Mature nodule on pea
roots
13 Legume-Rhizobium Symbiosis: Secondary Metabolites, Free Radical Processes. . .
295
the cytoplasm of the nodule cell. This process occurs through endocytosis. The
individual bacteria are surrounded by a membrane of plant origin, within which they
further differentiate into N 2 -fixing bacteroids [63, 65, 69, 71]. The root cells rapidly
replicate, then stop the division, and begin to increase in size, forming a nodule
tissue [7, 70]. After the bacterial invasion in nodules, vascular-fibrous bundles
from the procambium of the central cylinder and then the leading elements of the
Fig. 1 Development of legume-rhizobium symbiosis. Scheme describes the formation of indeterminate nodules
Fig. 2 Mature nodule on pea
roots
13 Legume-Rhizobium Symbiosis: Secondary Metabolites, Free Radical Processes. . .
295