Modulations in plant water relations and tissue-specific osmoregulation by foliar-applied ascorbic acid and the induction of salt tolerance in maize plants

Plant water status and cellular osmotic adjustments play a key role in the salt tolerance of plants. An experiment was conducted to assess the influence of foliar-applied ascorbic acid (AsA) on the plant water relations, cellular osmotic adjustments, uptake, and accumulation of different ions in the two high yielding maize cultivars (Agaiti-2002 and EV-1098) at early growth stage under salt stress (120 mM NaCl). Salt stress altered growth, water relation attributes, osmolytes accumulation, and decreased the uptake of K+, Ca2+, P, and N, while increased the uptake and accumulation of Na+ in different plant parts (leaf, stem, and root). Exogenous AsA increased the accumulation of AsA in different plant parts, particularly in leaves and roots. Moreover, AsA application resulted in the accumulation of proline and glycinebetaine (GB) in the roots and leaves of both maize cultivars when under salt stress. Foliar application of AsA also increased the uptake of minerals such as K+, Ca2+, P, and N and decreased the uptake and accumulation of Na+ in different plant parts. Taken together, the AsA-induced enhanced accumulation of osmolytes (GB and proline) and AsA increased the K+/Na+ ratio, and more accumulation of beneficial nutrients in the roots and leaves enhanced water uptake from soil and reduced the negative effects of Na+ in the salt-stressed maize plants. The results suggested that foliar-applied AsA either accelerated the tissue-specific translocation of AsA or altered the de novo synthesis of AsA to mitigate the adverse effects of salinity in maize plants.