✍ Scribed by Esthel Ramaroson; Dr. Michael Schramm
No coin nor oath required. For personal study only.
Sesbania rostrata and fifteen species of Aeschjinomene are tropical legumes which can grow in flooded soils because they have both root and stem nodulation. They are of particular agronomic interest because of their potential for maintaining soil fertility. Three genera of rhizobia are associated symbiotically with these stem nodulating legumes: Rhizobium infects S. rostrata and some Aeschynomene species; Azorhizobium is specific to S. rostrafa and can live outside the plant; Brudyrhizobium infects only Aeschynomene species.
In S . rostrata root infection occurs by root hair curling, whereas stem nodulation is achieved by entry of bacteria at the site of emerging adventitious rootlets. Many studies have reported that infection by thread formation is observed on both roots and stems of S. rostrata.
In S. rostrata, the process of root infection has been shown to follow several stages: recognition and attachment of rhizobia to the root surfaces induction of root hair curling; formation of infection threads that guide bacteria to the adjacent cortical root cells; release of bacteria into the cytoplasm of host cells where they are enveloped by host plasmalemm.
Stem infection of S . rostrata has been shown to have four stages: rhizobial penetration in degenerated cortical cells through cracks at the site of emerging rootlcts; Rhizobium proliferates in the intercellular cavities and initiates meristematic nodules; infection threads form in the intercellular cavities and in the host cells; rhizobia are intercellularly released by an endmytotic process.
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