Root Exudates

Rhizosphere and the Phyllosphere
Rhizosphere Introduction
Rhizospher Effect
Nitrogen Fixation in the Rhizosphere
Alteration of Rhizosphere Microflora
Associative and Antagonistic Activities in the Rhizosphere
Root Exudates
Organic Compounds Detected in Plant Root Exudates
Fungistasis
Techniques of Rhizosphere
The Soil Dilution and Plate Count Method
The Soil Plate
The Soil Box
The Contact Slide Technique
Artificial Rhizosphere
Model System

Root Exudates

	Root Exudates Most of the studies on root exudates have been done in plants grown under aseptic conditions. One of the most important factors responsible for rhizosphere effect is the great variety of organic substances available at the root region by way of exudates from roots which directly or indirectly influence the quality and quantity of microorganisms in the root region. The substances exuded by plant roots include amino acids, sugars, organic acids, vitamins, nucleotides and many other unidentified substances. The nature of substances exuded by roots of plants has been summarized .
The nature and amount of substances exuded are dependent on the species of the plant, age and environmental conditions under which they grow. By the use of ¹⁴CO₂, it has been shown that products of photosynthesis are translocated to the root system and find their way into the rhizosphere in less than 12 hours, clearly indicating the influence of the metabolism of plants in determining the extent of rhizosphere effect. Further, radioactivity in the rhizosphere soil diminishes when samples are taken spatially away from the root system, thereby indicating that rhizosphere effect is centrifugal and would tend to diminish in soil where the ramification of the root system is less.
The root cap and areas of active growth are primary regions of root exudation and one of major sites of carbon release from seminal wheat roots into the soil happens to be the zone of root elongation. It has been suggested that exudation is either from root tips or regions at which lateral roots emerge from the main root.

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