TITLE Physiological functions and methane and oxygen exchange in Korean rice cultivars grown under controlled soil redox potential
AUTHOR J.D. Kim
Wetland Biogeochemistry Institute, Louisiana State University, Baton Rouge, LA 70803-7511, USA
A. Jugsujinda
Wetland Biogeochemistry Institute, Louisiana State University, Baton Rouge, LA 70803-7511, USA
A.A. Carbonell-Barrachina
Wetland Biogeochemistry Institute, Louisiana State University, Baton Rouge, LA 70803-7511, USA
R.D. DeLaune
Wetland Biogeochemistry Institute, Louisiana State University, Baton Rouge, LA 70803-7511, USA
W.H. Patrick Jr.
Wetland Biogeochemistry Institute, Louisiana State University, Baton Rouge, LA 70803-7511, USA
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ABSTRACT Two Korean rice varieties (Oryza sativa L., cv. Nonganbyeo and Dongjinbyeo) were grown under laboratory conditions in Crowley silt loam (fine, montmorillonitic, thermic fluvaquent) soil suspension maintained at different redox potential (Eh) levels (-150, +150 and +350 mV). Plant growth, aerenchyma formation, radial oxygen loss, net CO2 assimilation, CH4 production (soil) and emission were measured. In general, plant height, root length, dry weight and carbon fixation for Nonganbyeo decreased under strongly reduced conditions (-150 mV). For Dongjinbyeo only a decrease in CO2 fixation was observed at -150 mV as compared to moderately reduced conditions (+150 mV and +350 mV). Under strongly reduced conditions (-150 mV) root porosity was less than rice grown at the two higher redox levels. Since greatest soil methane production occurred under strongly reduced conditions (-150 mV) no emission from the two rice cultivars were measured under moderately reduced soil conditions. However, under the strongly reduced soil conditions where methane was formed, there were apparent differences in methane emission between the two varieties studied. Methane production in pot in which DJB was grown was approximately 50 times greater than that of NAB but net emission was only greater by the factor of 3. Net carbon assimilation varied depending on soil Eh. Reduced soil conditions (Eh -150 mV) decreased net photosynthesis for both varieties. Radial oxygen loss on the other hand was greatest at Eh -150 mV, and this can be attributed to more oxygen demand under more reduced soil conditions. Results demonstrate that the degree of soil reduction influences both rice growth and methane emission. Management practices should consider growing the two rice cultivars under moderately reduced soil conditions where best carbon fixation was measured. Growth under these conditions would also reduce methane emission to atmosphere.
KEYWORD Aerenchyma formation; Carbon dioxide fixation; Korea; Methane emission; Oryza sativa; Radial oxygen loss;
ARTICLE INFO Botanical Bulletin of Academia Sinica, Volume 40 Number 3 July 1999, page 185-191, 7 pages
PUBLISHER Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan, Republic of China