ISSN:
1432-1424
Keywords:
Ca2+ binding
;
Plasma membrane
;
Root cells
;
Surface charge density
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract The presence of Ca2+ ions in solution is vital for root growth. The plasma membrane is one of the first sites where competition between Ca2+ and other ions occurs. We studied the competition between Ca2+ and Na+ or Mg2+ for sorption sites on the plasma membrane of melon root cells. Sorption of 45Ca2+ to right-side-out PM vesicles of melon (Cucumis melo L.) roots (prepared by aqueous two-phase partitioning) was studied at various Ca2+ concentrations, in the presence of increasing concentrations of Na+ or Mg2+ chlorides. Experimentally determined amounts of Ca2+ sorbed to the plasma membrane vesicles agreed fairly well with those calculated from a competitive sorption model. The best fit of the model to the experimental data was obtained for an average surface area of 370 Å2 per charge, and binding coefficients for Na+, Mg2+ and Ca2+ of 0.8, 9 and 50 m -1, respectively. Our results suggest that nonphospholipid components in the plasma membrane contribute significantly to Ca2+ binding. The high affinity of Ca2+ binding to the plasma membrane found in this study might explain the specific role of Ca2+ in relieving salt stress in plant roots.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00211069
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