Integrated Environmental Biotechnology - Environmental Biotechnology: Theory and Application - page 260

The following brief description of the required interactions between plants
and microbes, the example used here being Rhizobium , should serve to illustrate
why such a goal is very difficult to achieve. Firstly, the plant is invaded by a
member of the Rhizobium family of free living soil bacteria. There is a specific
relationship between plant and bacterium such that only plants susceptible to that
particular member of the group may be infected. Genes involved in the infection
process and nodule formation called nod genes are coded for by the bacterium.
The nod genes are activated by a mixture of flavenoids released by the plant
into the region around the roots and thus the plant signals to the bacterium its
receptiveness to be infected.
After infection through the root hairs, the multiplying bacteria find their way
into the cells of the inner root cortex. They are drawn into the cell by endo-
cytosis shown in Figure 10.5 and so are present within the cell bounded by
Figure10.5 Rootnoduleformation