Enhanced proline synthesis may determine resistance to salt stress in tomato cultivars

The physiological and biochemical responses of tomato cultivars were studied at khyber pakhtunkhwa agricultural university,peshawar,pakistan during 2005-2006 for salt tolerance. tomato cultivars were roma rio super,roma v.f.,chinese 87-5,rio grand and super blocky and subjected to salt stress (75 mm nacl). fresh weight,dry weight,and ions sodium and potassium accumulation,na +/k + ratio and proline content were determined after imposing the tomato cultivars to nacl salt for 80 days. salt stress significantly decreased the fresh and dry weight in roma rio super,roma v.f,chinese 87-5 and rio grand,however,in super blocky the fresh and dry weight were enhanced under stress conditions. salinity stress increased sodium uptake from 191.828 to 436.170 μmg -1 d wt while potassium accumulation decreased from 1033.12 to 926.80 μmg -1 d wt resulting in higher na +/k + ratio in stressed (0.48 g) as compared to unstressed control (0.19). the mean proline contents also increased from 28.95 to 40.96 μm proline g -1 f. wt with the maximum increase (57.378%) in super blocky followed by rio grand (49.325%).