Structure of Actinorhizal Nodule

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Actinorhizal Plants Frankia Induced Nodulation Root Nodules Caused by Frankia Actinorhizal Symbiosis Cross Inoculation Experiments Isolation and Characteristics of Frankia Cultural Characteristics of Frankia Taxonomy of Frankia Entry of Frankia to the Host Plant Structure of Actinorhizal Nodule

Structure of Actinorhizal Nodule

Structure of Actinorhizal Nodule
There are two types of structural organisation in actinorhizal root nodules-the Alnus type and the Casuarina type.Alnus type of nodules have many lenticels on nodules providing ventilation while Casuarina type do not have ventilatory organs. Instead, those lateral roots that escape infection by Frankia develop into nodule roots serving as antennae for oxygen diffusion. Both the types of nodules differ from legume root nodules.

Alnus Type Root Nodule

A Coralloid Root Nodule With Arrested Growth of the Apical Meristem

A. Relatively Young Root Nodules Alnus Glutinosa Situ Water Culture Plant	B.Detached and Dived Alnus Glutinosa Root Nodules Showing the Dichotomous Branching of the Nodular Lobes	C. Field collected Root Nodules of Alnus Glutinosa Showing theri Globular Structure and the Size of Aged Root Nodules Bar Scale =1.0cm.	D.Cells of parenchyma of A.glutinosa nodules showing vesicles of the endophyte (Courtesy, J.H. Becking Wageningen)

Legume root nodules are characterized by a central uniformly infected bacteroid and leghaemoglobin containing zone surrounded by a tight inner cortex that limits gas diffusion with the vascular bundles lying outside the inner cortex. In actinorhizal nodules, however, there is a central vascular bundle surrounded by a cortex in which several pockets of Frankia inhabiting zones can be seen containing vesicles.

Scanning Electron Micrograph of Two Host Cells in an Alnus Glutinosa Nodule Showing Vesicular Structures of the Endophyte

Scanning Electron Micrograph of Two Host Cells in an Alnus Glutinosa Nodule Showing Vesicular Structures of the Endophyte.(Courtesy, J.H. Beacking Wageningen.)Bar Scale=5.0micro m

Barring those belonging to Casuarina types which have suberized cells containing the hyphal endophyte with swollen tips. The suberized cells in Casuarina type of nodules are impervious to air and hence provide protection to nitrogenase and to the swollen hyphal tips which are believed to be the sites of nitrogen fixation. .

Diagrammatic representation of How Internal Structure of Root Nodule of a Typical Actinorhizal Plant Differ:

A-Legume	B-Alnus	C-Caduarina Showing Upardly Oriented Nodule Lateral Roots

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Nitrogen Fixation and Assimilation Field Experiments on the Benefit of Frankia Inoculation Mycorrhizae and Actinorhizal Plants Proteoid Roots Genetics of Frankia Rhizobium Induced Root Nodulation of Parasponia Leaf Nodules Gymnosperm Nodules

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