Abstract :
The vacuole is a key site for the storage of salt in plants responding to salinity. In plant cells accumulating NaCl, the driving force for secondary active Na+ transport in to the vacuole is provided by the proton-motive-force generated across the tonoplast by V-type H+-ATPase that specifically inhibited by bafilomycin A1. In order to study of changes of vacuolar volume after salt stress, root meristematic cells and protoplasts from salt sensitive rice cultivar (Anbarboo) and salt tolerant cultivars (Gharib and Musa-tarom) treated with 100 mM NaCl, 200 mM mannitol, 20 nM bafilomycin A1, 100 mM NaCl complemented with 20 nM bafilomycin A1 and normal condition. The sampling carried out at 3, 8 and 24 hours after imposing treatments. The results showed that root meristematic cells and protoplasts of both tolerant cultivars, expanded their vacuolar volume after NaCl and Mannitol treatments. Although, increased vacuolar volume had considerably caused more rapidly in both tolerant cultivars within NaCl than that in mannitol solution with same osmotic potential indicating that the increase in vacuolar volume being a mechanism for the rapid adaptation of plant cells to salt stress, and not necessarily associated to growth. Also, our findings illustrated that the inhibitory effect of BAF on V-ATPase caused a decrease in vacuole volume of meristematic cells and protoplasts of tolerant cultivars after imposing NaCl plus BAF. While the relations between expanded vacuolar volumes of Anbarboo under NaCl treatment with V-ATPase function were not so strong, stable vacuolar volumes of Gharib and Musa-Tarom during 24-hours exposure of BAF plus NaCl indicating that V-ATPase functions in a significant biological mechanism. Therefore, both tolerant genotypes were probably able to use the controlled uptake of Na+ balanced by organic solutes in the cytoplasm for osmotic adjustment at the cellular level.
