Salt tolerance in rice in vitro: Implication of accumulation of Na+, K+ and proline

The implication of accumulation of both inorganic (Na+, K+) and organic (proline) solutes were evaluated in unadapted and NaCl-adapted callus of a salt-sensitive (Basmati 370) and a salt-tolerant (SR-26B) cultivar of rice (Oryza sativa L.) after a NaCl shock. Accumulation of Na+,K+ and/or proline in callus was co relatable and the relative presence of these components in tissues after shock treatment was found to be important factors to support differential regrowth capacities of the shock treated calluses. Presence or retention of K+ in rice callus was a key factor for salt tolerance as it was observed to be positively correlated with growth in both the varieties. The results indicated that K+ was the first candidate to counteract the negative water potential of outside milieu, while proline was probably the last metabolic device that rice calluses opted for when exposed to salt stress.