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Development and growth effects in the Sorghum–Azospirillum association
Author(s) -
Pacovsky R.S.
Publication year - 1990
Publication title -
journal of applied bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 0021-8847
DOI - 10.1111/j.1365-2672.1990.tb05220.x
Subject(s) - sorghum , azospirillum brasilense , microbial inoculant , inoculation , biology , shoot , agronomy , nutrient , persistence (discontinuity) , horticulture , ecology , geotechnical engineering , engineering
Sorghum plants were inoculated with a pigmented strain of Azospirillum brasilense (Cd) or were not inoculated and received an N‐amended nutrient solution (1.0 mmol/l NH 4 NO 3 ). A third set of plants were non‐inoculated and not fertilized with N (control). Plants were grown in a steam‐sterilized, low‐fertility soil and harvested after growing for 2, 4, 6, 8 and 10 weeks. Dry weights for Azospirillum ‐inoculated plants were significantly greater than the N‐fertilized sorghum at weeks 2 and 4, but A. brasilense ‐colonized plants weighed significantly less than the N‐fertilized sorghum at weeks 8 and 10. Shoot and root N concentrations increased for N‐amended plants but remained fairly steady for sorghum inoculated with strain Cd indicating enhanced N‐use efficiency in plants colonized with the endophyte. In general, the concentration of Fe, Mn, Zn and Cu in Azospirillum ‐colonized plants was relatively less than that in N‐amended sorghum early in ontogeny when the growth rate of the inoculated plants was greatest. The number of inoculated Cd cells per plant was correlated with percentage increase in dry weight ( r = 0.92*) or total N content ( r = 0.93*) relative to the N‐fertilized plants. Growth enhancement relative to N‐fertilized sorghum was not observed when the number of Azospirillum cells per gram of root dropped below 1.0 x 10 5 (or 3.0 x 10 6 cells/plant). Therefore, the persistence of Azospirillum in the endorhizosphere of sorghum had a direct impact on host growth, physiology and nutrition.