Potassium application mitigates salt stress differentially at different growth stages in tolerant and sensitive maize hybrids

A pot experiment was conducted to investigate the role of potassium (K) in extenuating the injurious effect of salt stress on maize hybrids differing in salt tolerance at different growth stages. One salt-sensitive viz. 8441 and one salt-tolerant viz. 26,204 maize hybrids were sown in pots having 12 kg soil. The recommended dose of nitrogen and phosphorus @ 200 and 150 kg ha with different rate of potassium (75, 150 and 300 kg ha) and salinity level (10 dS m) was developed in soil before filling the pots. Salinity stress reduced plant growth by affecting plant morphological characteristics, reducing relative water contents and membrane stability index, decreasing photosynthetic activities, altering K/Na ratios and antioxidant activities of both maize hybrids at all three growth stages. However, results also depicts that maximum relative water contents, membrane stability index, gas exchange attributes, photosynthetic pigments, antioxidant enzymes activities and proline contents was observed at reproductive growth stage as compared to vegetative and grain development growth stages in both hybrids. The inhibitory effect of salt stress was more pronounced on maize hybrid 8441 than 26,204. But, addition of potassium significantly alleviates harmful effect of salinity by improving the plant growth, gas exchange parameters, enhancing K/Na ratios and antioxidant activities of both maize hybrids. Potassium application (300 kg K ha) was found more effective in alleviating perilous effect of salinity as compared to other two levels. Salt tolerant maize hybrid (26,204) produced more biomass, less shoot Na concentration, high K concentration, exhibited more chlorophyll contents, gas exchange parameters and antioxidant enzymes activities under salt stress condition at all growth stages as compared to salt sensitive maize hybrids (8441). These results suggested that potassium application counteracted the unfavorable effects of salinity on growth of maize by civilizing photosynthetic capacity of maize plants against salinity-induced oxidative stress and maintaining ion homeostasis, however, these alleviating effects were cultivar specific.