Nitrogen fixation associated with deepwater rice

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Abstract
N2 fixation associated with deepwater rice was studied by exposing aquatic parts of deepwater rice to 15N2 gas for 9 days. Higher enrichment of 15N from molecular nitrogen was found in the aquatic root and leaf sheath where blue-green algae grow epiphytically. Eight mg Njplant were fixed during this period and about 40% of fixed nitrogen was found at maturity in the portions that were not directly exposed to 15N2 Simultaneously with 15N2-feeding experiments, rice was grown in pots containing 15N-labeled ammonium sulfate in shallow water and deep water ( < 120 cm). Rice plants in deepwater had lower 16N enrichment. Leaf sheaths and roots under water had lower 15N content than other parts. 15N contents of various parts in the 15N2-feeding experiment were inversely proportional to 15N content in the 15N-dilution experiment.