Effect of potassium application on ammonium nutrition in maize (Zea mays L.) under salt stress.

Application of potassium has been found to minimize the toxic effect of NH4+ under salt stress. To study the interactive effect of K+ and NH4+ under saline condition, maize (Zea mays L., cv. Pioneer-3335) was grown in a hydroponic culture with ammonium (5.0 and 10 mM) as (NH4)(2)SO4 at two different levels (3.0 and 9.0 mM) of K+ under control and 100 mM NaCl. Under saline condition, 5 mM NH4+ application along with 3.0 mM K+ decreased the dry mass by 24% in maize while its addition at the rate of 10 mM showed a percent decline upto 70% than the control. A decrease in shoot dry mass induced by the combine application of 5.0 mM NH4+ and 9.0 mM K+ was 19% relative to control whilst a decrease i.e. 52% was observed at 10 mM NH4+ level. The increasing concentration of potassium was found to alleviate the NH4+ toxicity and salinity stress partly by inhibiting the uptake of NH4+ and Na+ and by stimulating the N assimilation in plant body. Growth improvement at combination of 5.0 mM NH4+ and 9.0 mM K+ was reinforced by higher K+ influx into root cells and its translocation to the growing tissues. Elevating the K+ supply also resulted in the enhanced plant growth several times and reduction in NH4+ toxicity and salinity stress.