MORPHOLOGICAL RESPONSE AND ION REGULATION IN MAIZE (ZEA MAYS L.) VARIETIES UNDER SALT STRESS

A screening study was conducted in order to determine the genotypic differences of 20 maize varieties, and to evaluate the mechanism of ion regulation under salt stress conditions. The study was arranged in a completely randomized plot design with 4 replications under controlled conditions in 2013. Seeds were planted in plastic pots with a mixture of peat:perlite at a ratio of 2:1. At 27 days after sowing, the salt (NaCl) treatment was started. The varieties were classified according to the severity of the leaf damage symptoms, using symptoms score of 1-5. The fresh and dry shoot weights, fresh and dry root weight, leaf number, plant height, stem diameter, relative water content, and the shoot and root concentrations of sodium, potassium, calcium, and chlorine were also investigated. The varieties exposed to 250 mM NaCl application developed different mechanisms to be protected against toxic effects of Na ion. Salt tolerant varieties limited Na accumulation and acted selectively among ions. K and Ca concentrations were high in shoot and root in which Na concentration was low, and tolerant varieties had higher K/Na and Ca/Na ratios than sensitive varieties. In conclusion, the maize varieties showed a wide variation in their response to salt stress. Reliable and effective screening parameters, such as scale, shoot and root fresh-dry weight, ion content, for determination of salt tolerance level of the maize varieties were discussed. Overall findings suggest that PG 1661, Ada 523, Colonia, PG Pasha, and PG 1610 varieties were more tolerant varieties than the other ones.