Abstract
Changes in exudation rate and cytokinin activities in the exudates were measured in two varieties of rice (Oryza sativa L.), cv Nipponbare (a Japanese normal cultivar) and cv Akenohoshi (a high-yielding cultivar). The exudation rates of Akenohoshi, the leaves of which remained green for a longer time, were higher than those of Nipponbare after the booting stage. Cytokinin activities in the exudates of Akenohoshi were higher than those of Nipponbare during the ripening period. Cytokinins in the exudates collected during the middle of the ripening stage were analyzed with mass spectrometry using deuterium-labeled standards. trans-Zeatin, trans-ribosylzeatin, and N6-isopentenyladenosine were detected as free cytokinins, and zeatin was detected in the hydrolysates of highly polar fractions (“conjugated zeatin”) in the exudates of both cultivars. Conjugated zeatin was the predominant cytokinin in both cultivars. Therefore, we suggest that conjugated zeatin is an important form of cytokinin during the ripening stage. The level of each of the cytokinins in Akenohoshi was higher than that in Nipponbare. Also, we discuss the correlation between the leaf senescence and cytokinin content in root exudates.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Arnon D. I. COPPER ENZYMES IN ISOLATED CHLOROPLASTS. POLYPHENOLOXIDASE IN BETA VULGARIS. Plant Physiol. 1949 Jan;24(1):1–15. doi: 10.1104/pp.24.1.1. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hashizume T., Sugiyama T., Imura M., Cory H. T., Scott M. F., McCloskey J. A. Determination of cytokinins by mass spectrometry based on stable isotope dilution. Anal Biochem. 1979 Jan 1;92(1):111–122. doi: 10.1016/0003-2697(79)90631-6. [DOI] [PubMed] [Google Scholar]
- Heindl J. C., Carlson D. R., Brun W. A., Brenner M. L. Ontogenetic variation of four cytokinins in soybean root pressure exudate. Plant Physiol. 1982 Dec;70(6):1619–1625. doi: 10.1104/pp.70.6.1619. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Noodén L. D., Singh S., Letham D. S. Correlation of xylem sap cytokinin levels with monocarpic senescence in soybean. Plant Physiol. 1990 May;93(1):33–39. doi: 10.1104/pp.93.1.33. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Short K. C., Torrey J. G. Cytokinins in seedling roots of pea. Plant Physiol. 1972 Feb;49(2):155–160. doi: 10.1104/pp.49.2.155. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sugiyama T., Hashizume T. Mass spectrometric determination of cytokinins in the top of tobacco plants using deuterium-labeled standards. Nucleic Acids Symp Ser. 1982;(11):61–64. [PubMed] [Google Scholar]