Abstract

Amino sugar nitrogen (ASN) is one of the most important nitrogen sources for plants. Whether ASN such as glucosamine can be absorbed directly by plants has remained unclear, because the technology for investigating its mechanism of absorption has been lacking. Using Positron Emission Tomography (PET) with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG), we observed that ASN was absorbed directly by tomatoes and rice and this absorption was significantly influenced by the carbon to nitrogen ratio (C/N) and the pH value of the growth substrate solution of tomatoes and rice. Absorption and transportation of ASN was measured at C/N ratios of 10 or 25 at pH 7.0 or 8.0 in tomato and at pH 5.5 or 6.5 in rice. A C/N ratio of 10 resulted in higher ASN absorption and transportation than a C/N ratio of 25 in both tomatoes and rice. At C/N ratio of 10, tomatoes absorbed more ASN at pH 8.0 than at pH 7.0. In rice, absorption was more at pH 5.5 than 6.5. In a word, a lower C/N ratio yielded a higher ASN absorption and transportation for both tomatoes and rice. Tomatoes showed a slight preference for alkaline conditions, whereas rice preferred acidic conditions.

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