Uptake of sodium in protoplasts of salt-sensitive and salt-tolerant cultivars of rice, Oryza sativa L. determined by the fluorescent dye SBFI.
In this study, the uptake of Na+ into the cytosol of rice (Oryza sativa L. cvs Pokkali and BRRI Dhan29) protoplasts was measured using the acetoxy methyl ester of the fluorescent sodium-binding benzofuran isopthalate, SBFI-AM, and fluorescence microscopy. By means of inhibitor analyses the mechanisms for uptake and sequestration of Na+ in the salt-sensitive indica rice cv. BRRI Dhan29 and in the salt-tolerant indica rice cv. Pokkali were detected. Less Na+ was taken up into the cytosol of Pokkali than into BRRI Dhan29. The results indicate that K+-selective channels do not contribute to the Na+ uptake in Pokkali, whereas they are the major pathways for Na+ uptake in BRRI Dhan29 along with non-selective cation channels. However, non-selective cation channels seem to be the main pathways for Na+ uptake in Pokkali. Protoplasts from Pokkali leaves took up Na+ only transiently in the presence of extracellular Na+ at 5-100 mM. Therefore, it is likely that the protoplasts have a mechanism for fast extrusion of Na+ out of the cytoplasm. Experiments with protoplasts pretreated with NH4NO3 and NH4VO3 suggest that the salt-tolerant Pokkali extrudes Na+ mainly into the vacuole. After cultivation of both cultivars in the presence of 10 or 50 mM NaCl for 72 h, the isolated protoplasts from Pokkali took up less Na+ than the control protoplasts. The results suggest that the salt-tolerance in Pokkali depends on reduced uptake through K+-selective channels and a fast extrusion of Na+ into the vacuoles.
Kader
Md Abdul
MA
Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, Box 7080, SE 750 07 Uppsala, Sweden.
Lindberg
Sylvia
S
D001572:Benzofurans; D003600:Cytosol / Q000737:chemistry; D004988:Ethers, Cyclic; D005456:Fluorescent Dyes; D017136:Ion Transport / Q000502:physiology; D012275:Oryza / Q000737:chemistry / Q000378:metabolism*; D009994:Osmolar Concentration; D018515:Plant Leaves / Q000737:chemistry / Q000378:metabolism; D018517:Plant Roots / Q000737:chemistry / Q000378:metabolism; D011523:Protoplasts / Q000737:chemistry / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D012964:Sodium / Q000032:analysis / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology; D014783:Viscosity
D001572:Benzofurans; D004988:Ethers, Cyclic; D005456:Fluorescent Dyes; C061665:sodium-binding benzofuran isophthalate; D012965:Sodium Chloride; D012964:Sodium