Rhizosphere Interactions

Introduction

The rizosphere refers to the region of soil near plant roots. Compared to the rest of soil, this area is relatively luxurious- nutrients are more plentiful and bacteria abound. Sylvia et al compare the rizosphere to an oasis.

Soil Environment Associated with Plants

Rhizoplane

The rizoplane refers to the environment in immediate physical contact with the roots. Microbes that live in the rizoplane are closer to the actual roots than the microbes in the risosphere. The functional definition is everything remaining after the roots have been shaken vigorously in water. There are more microbes (as counted by CFU) in the rizoplane than in the more loosely assoicated rizosphere. Those microbes who are directly in contact with the roots tend to be found where the integrety of the root is broken. Perhaps because of this, they also tend to be found on older rather than younger roots. The distinction between bacteria which live in the rizoplane and those who live inside the root is made by naming the latter "endophytes"

Rhizosphere

There are several subjective definitions of “rhizosphere” one is the zone of influence of plant roots- that may vary for the specific influence being tracked and the specific environment. A more general, functional definition is “the dirt that clings to roots after gentle shaking in water”. In general the rizosphere is a metabolically busier, faster moving, more competitive environment than the surrounding soil.

References

• Sylvia, D., Fuhrmann,J., Hartel, P., Zuberer, D. 2005. Principles and Applications of Soil Microbiology. Pearson Education Inc. New Jersey.

Edited by students of Kate Scow