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Publication Type J
Authors Agarie, S., T. Shimoda, Y. Shimizu, K. Baumann, H. Sunagawa, A. Kondo, O. Ueno, T. Nakahara, A. Nose and J. C. Cushman
Title Salt tolerance, salt accumulation, and ionic homeostasis in an epidermal bladder-cell-less mutant of the common ice plant Mesembryanthemum crystallinum
Source Journal of Experimental Botany
Author Keywords epidermal bladder cells; halophyte; ice plant; ion homeostasis; Mesembryanthemum crystallinum; salt stress; succulence crassulacean-acid-metabolism; sporobolus virginicus; na+/h+-antiport; water relations; high salinity; stress; expression; ultrastructure; transporters; responses
Abstract The aerial surfaces of the common or crystalline ice plant Mesembryanthemum crystallinum L., a halophytic, facultative crassulacean acid metabolism species, are covered with specialized trichome cells called epidermal bladder cells (EBCs). EBCs are thought to serve as a peripheral salinity and/or water storage organ to improve survival under high salinity or water deficit stress conditions. However, the exact contribution of EBCs to salt tolerance in the ice plant remains poorly understood. An M. crystallinum mutant lacking EBCs was isolated from plant collections mutagenized by fast neutron irradiation. Light and electron microscopy revealed that mutant plants lacked EBCs on all surfaces of leaves and stems. Dry weight gain of aerial parts of the mutant was almost half that of wild-type plants after 3 weeks of growth at 400 mM NaC1. The E-BC mutant also showed reduced leaf succulence and leaf and stem water contents compared with wild-type plants. Aerial tissues of wild-type plants had approxirnately 1.5-fold higher Na+ and Cl- content than the mutant grown under 400 mM NaCl for 2 weeks. Na+ and Cl- partitioning into EBCs of wild-type plants resulted in lower concentrations of these ions in photosynthetically active leaf tissues than in loaves of the EBC-less mutant, particularly under conditions of high salt stress. Potassium, nitrate, and phosphate ion content decreased with incorporation of NaCl into tissues in both the wild type and the mutant, but the ratios of Na+/K+ and Cl-/ NO3- content were maintained only in the leaf and stem tissues of wild-type plants. The EBC mutant showed significant impairment in plant productivity under salt stress as evaluated by seed pod and seed number and average seed weight. These results clearly show that EBCs contribute to succulence by serving as a water storage reservoir and to salt tolerance by maintaining ion sequestration and homeostasis within photosynthetically active tissues of M. crystaffinum.
Author Address Univ Nevada, Dept Biochem & Mol Biol, Reno, NV 89557 USA. Saga Univ, Fac Agr, Saga 8408502, Japan. Meijo Univ, Fac Agr, Tempaku Ku, Nagoya, Aichi 4688502, Japan. Natl Inst Agrobiol Sci, Plant Physiol Dept, Tsukuba, Ibaraki 3058602, Japan. Kyushu Elect Power Co Inc, Res Lab, Bioresources Res Ctr, Saga 8490922, Japan. Cushman, JC, Univ Nevada, Dept Biochem & Mol Biol, MS200, Reno, NV 89557 USA. jcushman@unr.edu
29-Character Source Abbreviation J. Exp. Bot.
Year Published 2007
Volume 58
Issue 8
Beginning Page 1957-1967
Unique Article Identifier ISI:000248447500005
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