Plant and Cell Physiology Advance Access originally published online on July 18, 2007
Plant and Cell Physiology 2007 48(8):1219-1228; doi:10.1093/pcp/pcm092
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A Wilty Mutant of Rice has Impaired Hydraulic Conductance
1Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo, 183-8509 Japan
2Graduate School of Agriculture, Kyushu University, Hakozaki, Higashi-ku, Fukuoka, 812-8581 Japan
*Corresponding author: E-mail, hirasawa{at}cc.tuat.ac.jp; Fax, +81-42-367-5671.
| Abstract |
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The rice CM2088 mutant is the wilty phenotype and wilts markedly under well-watered sunny conditions. The leaf water potential and epidermal (mainly stomatal) conductance of CM2088 plants decreased significantly under conditions that induced intense transpiration, as compared with those of wild-type plants, revealing that the wilty phenotype was not the result of abnormal stomatal behavior but was due to an increase in resistance to water transport. The resistance to water transport was dramatically elevated in the node and the sheath and blade of a leaf of the mutant, but not in the root or stem. The diameter of xylem vessels in the large vascular bundles of the leaf sheath and the internode tended to be small, and the numbers of vessel elements with narrowed or scalariform perforation plates in the leaf blade and sheath were greater in the mutant than in the wild type. Most xylem vessels were occluded, with air bubbles in the leaf sheath of the mutant during the midday hours under intense transpiration conditions, while no bubbles were observed in plants that were barely transpiring, revealing that the significant increase in resistance to water transport was a result of the cavitation. The additive effects of cavitation in xylem vessels and the decreased diameter and deformed plates of vessel elements might be responsible for the wilty phenotype of CM2088.
Keywords: Cavitation - Diffusive conductance - Resistance to water transport - Rice - Water potential - Wilty mutant
Abbreviations: NMN, N-methyl-N-nitrosourea
3Present address: Department of Biology, School of Art and Science, University of Pennsylvania, 415 South University Avenue, Philadelphia, PA 19104-6018, USA.
(Received January 2, 2007; Accepted July 9, 2007)
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