Foliar application of thiourea, salicylic acid, and kinetin alleviate salinity stress in maize grown under etiolated and de-etiolated conditions

Abstract

Salinity stress and the absence of light negatively impact growth and development of the plants. Morpho-physiological and biochemical attributes of maize (Zea mays L.) get severely affected by salt stress and subdue light. Therefore, a pot experiment was conducted under the prevailing environmental conditions of Turbat, Balochistan, to explore etiolation and the de-etiolation response of maize hybrid (SP-17S23) to salinity stress under exogenous application of plant growth regulators (PGRs). Maize seedlings in three sets, i.e., non-etiolated, etiolated, de-etiolated, subjected to salinity stress (120 mM NaCl) after 15 days of seed germination. After a week, the seedlings were sprayed with optimized levels of different PGRs, including thiourea (TU; 10 mM), salicylic acid (SA; 250 µM), and kinetin (KIN; 3 µM). Salinity stress hampered plant growth and affected morpho-physiological attributes. However, PGRs foliar treatment proved effective, thus ameliorating the impact of salinity and etiolation on maize seedlings. Growth attributes (root/shoot length, leaf area, root/shoot fresh and dry weight), photosynthetic pigments (Chl a, b and carotenoids) were significantly enhanced under the foliar treatment of PGRs, especially under TU and KIN treatments. However, the oxidative damage parameters, i.e., malondialdehyde (MDA) and hydrogen peroxide (H2O2), decreased under the treatment of PGRs, thereby protecting seedlings under salinity and etiolated conditions. Overall, PGRs enhanced tolerance potential of plants under salinity stress with the consideration of light variations remain the key concern for developing healthy and vigor seedling strands.