Growth responses of paddy rice to an ammonia-excreting mutant cyanobacterium at elevated CO2 concentration
1994
Kamuru, F. | Albrecht, S.L. | Baker, J.T. | Allen, L.H. Jr | Shanmugam, K.T.
An ammonia-excreting mutant strain of Anabaena variabilis (strain SA-1) was studied as a N supplier for the growth of rice (Oryza sativa L., cultivar 'IR-30') plants at near ambient (330 μmol mol-1) and elevated (660 μmol mol-1 carbon dioxide (CO2) concentrations. Rice performance with N supplied by the mutant cyanobacterium was compared with that of three other N treatments: rice plants inoculated with the parent strain (A. variabilis, strain SA-0), plants fertilized with 75 Kg N ha-1 as urea, or control plants (uninoculated, with no nitrogen fertilization). Plants at elevated CO2 concentration had a higher dry matter content and accumulated more nitrogen than at near ambient CO2. At either CO2 concentration, the mutant strain enhanced the shoot and grain dry matter accumulation more than did the parent strain. Total N concentration of the shoot and grain fractions was significantly greater (P < 0.05) in plants inoculated with the mutant than with the shoot and grain the cyanobacterium. The benefit of inoculation with the ammonia-excreting mutant strain was equivalent to or greater than the response observed in plants receiving 75 kg N ha-1. A combined response of both the rice plants and the cyanobacterium to high CO2 levels probably accounted for the higher dry matter and N at the elevated than at the ambient CO2 concentration. The potential of the ammonia-excreting mutant cyanobacterium as a N source for sustainable, low-input rice production in the predicted high CO2 atmosphere of the next century is promising.
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