Changes in Organic and Inorganic Osmolytes of Maize (Zea mays L.) by Sulfur Application Under Salt Stress Conditions

Mineral nutrients have favourable potential in alleviation of salinity problem in plants. Sulfur has specific functions in regulating plant growth, metabolism, enzymatic reactions and osmolyte homeostasis in plants. Hence, an experiment was carried out to explore the role of sulfur in ameliorating salt toxicity in maize by changes in organic and inorganic osmolyte contents. A range of sulfur levels (40, 80 mM) were used to induce salinity tolerance in maize. Various treatments of salinity (25, 75 mM) were applied by using sodium chloride. Results revealed that glycine betaine, proline, total soluble sugars, total soluble proteins and total free amino acids contents were increased by applying salinity while the application of sulfur lowered the proline and increased other studied organic osmolyte contents in all studied maize organs (leaf, shoot, root). The maximum improvement in organic osmolyte contents were found at 40 mM sulfur, however, at 80 mM sulfur proline contents were reduced. Applied salinity increased leaf tissue concentration of Na+ and decreased that of K+, Ca2+, NO3-, PO43-, SO42- leading to a severely declined in K+/Na and Ca2+/Na+ ratio. However, application of sulfur reduced the Na+ contents and improved K+, Ca2+, NO3-, PO43-, SO42-, K+/Na+ and Ca2+/Na+ ratio in the salinity grown plants. Moreover, 40 mM level of sulfur was greatly effective in osmolyte homeostasis at all levels of salinity. This indicated that use of sulfur (40 mM) ameliorated the effect of salinity by changing organic and inorganic osmolyte contents in maize plants.