Exogenously applied silicate and abscisic acid ameliorates the growth of salinity stressed wheat (Triticum aestivum L) seedlings through Na + exclusion

Hydroponic experiments were conducted to investigate the possible role of abscisic acid (ABA) and silicate (Si) on inducing salinity tolerance in wheat seedlings. Caryopses of two wheat genotypes Kharchia-65 (salt tolerant) and Punjab-85 (salt sensitive) were pre- treated with ABA (10 m M) for 24 h. Ten-day-old seedlings were exposed to 100 mM NaCl solution containing either 0 mM or 3 mM of sodium silicate for 16 days. We employed a fluorescent tracer trisodium salt of 8-hydroxy-1, 3, 6-pyrenetrisulphonic acid (PTS) for estimating Na + transport pathway to shoot. Exogenously applied Si as alone or with ABA significantly improved seedling growth by inhibiting Na + transport and the Na/ + K + ratio in both wheat genotypes. The genotype Punjab-85 maintained higher apoplastic Na + concentration compared to Kharchia-65 under NaCl treatment. Moreover, Si and ABA application improved leaf chlorophyll contents and consequently net assimilation rate of NaCl- stressed wheat seedlings through up-regulation of antioxidative enzyme activities. The results suggested that application of Si alone or in combination with ABA can significantly limit Na + bypass flow in both salt sensitive and tolerant wheat genotypes; however, ABA alone was effective in sensitive genotype only (Punjab-85). It is inferred from the results that Si had a more prominent role than ABA on plants in increasing biomass accumulation, proline contents and antioxidant enzyme activities, and inhibiting Na + accumulation and bypass flow. Nevertheless, ABA assisted Si in the