Selected Bihliogiaphv 259 



those oruaiiisins c1c[)i'ik1,s u[-)()n tlic nature ot the residues, tlie nature 

 ot the soil, and the cmu ironnuMital eonditions. 



Bacterization 



Tlie term "baeterization" lias been applied to soil and seed inocula- 

 tion with bacteria and otlier microorganisms either to stimulate plant 

 growth or to combat the attack on plants by various pathogenic fungi 

 and bacteria. There is no doubt of the favorable effect upon the 

 growth of leguminous plants of seed or soil inoculation when prop- 

 erly adapted cultures are used. This is true also of certain mycor- 

 rhiza fungi upon nursery plants, especially on trees not previously 

 grown in a given area. The favorable effect, however, upon wheat 

 or other cereal plants or upon sugar beets of inoculation with Azoto- 

 bacter or other bacteria has not been established. In summarizing 

 these results, Jensen questioned the premise of nitrogen fixation by 

 Azotobacter, although he was inclined to accept the favorable effect 

 of growth factors elaborated by bacteria. Allison, as well, submitted 

 to severe criticism the value of the experiments on the use of Azoto- 

 bacter as a seed inoculant. He examined in detail the claims made 

 for the beneficial effects of such inoculation, that (a) nitrogen is 

 fixed by the bacteria living in the rhizosphere, largely on the root 

 excretions; (b) the added bacteria protect the plants against patho- 

 genic microorganisms either by discouraging their growth or by 

 destroying them; (c) the bacteria stimulate plant growth through 

 the production of hormones, auxins, vitamins, and other growth ac- 

 celerators or regulators. The last claim was considered the only 

 plausible one that may be of any significance as regards seed inocu- 

 lation. 



Selected Bibliography 



1. Allisun, F. E., Azotobacter inoculation of crops. I. Historical, Soil Sci., 64: 

 413-429, 1947. 



2. Clark, F. E., Soil microorganisms and plant roots, Advances in Af^ron., 1: 

 241-288, 1949. 



3. Crafts, A. S., Mo\ement ot \iruses, auxins, and chemical indicators in plants, 

 Botan. Rev., 5:471-504, 1939. 



4. Garrett, S. D., Ecology of the root-inhabiting fungi, Biol. Revs., 25:220-254, 

 1950. 



5. Gerretsen, F. C, The influence of microorganisms on the phosphate intake 

 by the plant, Plant and Soil, 1:51-81, 1948. 



