Salt induced changes in germinating seeds of salt tolerant and salt sensitive lines of spring wheat

The seeds of salt tolerant line, SARC-I and salt sensitive line, Blue Silver were subjected for seven days to salinized solution culture containing 0 and 150-mol m-3 NaCl. Data for different biochemical and mineral elements were recorded daily after the start of germination. A time course increase in fresh weights of plumule and radicle was observed in saline conditions in both cultivars, whereas that of germinating seed had a decreasing trend with time. Comparison of the cultivars of radicle was more in Blue Silver than that in SARC-1 under saline conditions. The saline medium had no significant effect on dry weights of plumule and radicle of both cultivars of wheat but significant effect on seed dry weights of both cultivars was observed. Varieties showed similar pattern of reduction in dry weight as that of fresh weight. Saline growth medium had a significant effect on Na+ concentrations of plumule, radical and seed. Overall, Na+ concentration in radicals of both cultivars was much higher in saline and non-saline conditions. The pattern concentrations of accumulation of Cl- in different embryonic parts was not consistent in both the cultivars with time. Thus, it is, not possible to draw any parallel between Cl- concentration and the growth of different embryonic parts in both the, lines under saline and non- saline condition. K+ concentration in seed and radicle of both cultivars decreased considerably with time under saline conditions whereas that in plumule no clear-cut trend of increase or decrease was found. Ca+ concentration of plumule in both lines decreased consistently in saline condition but maximum Ca2+ accumulation in Blue Silver was observed at day 7 of germination. Seed Ca2+ had a fluctuated pattern upto day 4th of germination but thereafter there was a sharp decline in Ca2+ concentration in saline and non-saline conditions. External salt regimes had a significant effect on K/NA ratio of the plumule and radicle. Varieties differed non- significantly with respect to radicle and seed K/Na and Ca/Na ratio. Total soluble sugars of plumule of both varieties decreased significantly with time of germination whereas that of radicle and SARC-I under saline condition a- amylase activity generally increased with time in all three, parts of germinating seed in both the cultivars. Although salt stress was found to slightly inhibit the a-amylase activity in all parts of germinating seed, it was not possible to discriminate between the varieties on the basis of a- amylase activity under salt stress. Soluble protein content of all embryonic organs of the germinating seeds of two wheat cultivars decreased significantly after 7 days of germination. Generally, Blue Silver had higher amount of soluble protein in radicle than that in SARC-I under both saline and non-saline conditions. Protease activity also increased considerably with time in all three parts of germinating seeds of both cultivars under saline and non-saline conditions. However, there was slight inhibitory effect of salt stress on protease activity in both the cultivars. The maximum adverse effect of salt stress on protease activity was observed in the germinating seeds of Blue Silver. There was a significant reduction in free amino acids content of both wheat cultivars. Varieties also differed significantly with respect to free amino acids of all three different parts of germinating seeds of both cultivars. Although there was a significant effect of salt stress on proline contents of all three different parts of germinating seeds of both cultivars, there was no consistent pattern of proline accumulation with time. Thus it was not easy to compare the varieties with respect to proline content of either seed part. The results suggests that the inhibition of germination, reduced activity of two hydrolytic enzymes a-amylase and protease and the metabolic sequence induced by them are delayed under salt stress. Overall higher K/Na ratio, increased total soluble sugars and proline content in SARC-1 suggest that these attributes are responsible for its higher salt tolerance as compared to Blue Silver.