Alteration of Rhizosphere Microflora

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

Alteration of Rhizosphere Microflora

	Alteration of Rhizosphere microflora There are reports of changes in the rhizosphere microflora by (1) soil amendments; (2) foliar application of nutrients; and (3) artificial inoculation of seed or soil with preparations containing live microorganisms, especially bacteria (bacterization). Many experiments have been done to find out the effects of N, P and K additions on rhizosphere microflora. The results do not lend themselves to any generalization since increase as well as decrease in R : S ratios have been reported as a sequel to fertilizer applications.
Translocation of photosynthates from leaves to roots is a well-known phenomenon as part of the normal metabolic activity of plants. Therefore, it is logical to assume that if materials artificially applied to leaves get into the leaf tissue, translocation may not pose difficult problems. In fact, many workers have reported the recovery of compounds (2,3,6-trichlorobenzoic acid; a-methoxyphenylacetic acid; 2-methoxy-3,6-dichlorobenzoic acid; 2, 4, 5- T; streptomycin) sprayed on leaves from root exudates of plants. Foliar sprays of urea are known to alter the number and nature of microorganisms in the rhizosphere.
Extensive studies have been done on induced changes in the rhizosphere microflora by foliar sprays of antibiotics, growth regulators, pesticides and inorganic nutrients in the hope that such an approach may serve as a new tool in biological control of root diseases. However, no definite conclusions or guidelines have emerged from such studies to merit their application under field conditions.
Microbial seed inoculants such as Azotobacter, Beijerinc1cia, Rhizobium or P-solubilizing microorganisms may help in the establishment of beneficial microorganisms in the rhizosphere or in the immediate vicinity of growing roots. Field experiments have shown that counts of Azotobacter in wheat rhizosphere increased upon artificial seed inoculation indicating the efficiency of bacterization as a means of altering and improving the rhizosphere microflora.

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