Exogenous triacontanol-mediated increase in phenolics, proline, activity of nitrate reductase, and shoot k+ confers salt tolerance in maize (Zea mays L.)

Triacontanol (TRIA) has been shown to regulate growth in some crop species exposed to stressful environments. In the present study, we assessed whether or not and to what extent foliar-applied TRIA can alter metabolism and nutrient uptake, and thus induce salt tolerance in maize (Zea mays L.). For this purpose, 14-day-old plants of two maize cultivars (MMRI-Yellow and Hybrid S-515) were subjected to salt stress (0 mM and 100 mM NaCl). 21-day-old plants were exogenously treated with different concentrations (0, 2, 5 µM) of TRIA. After 51 days of TRIA treatment (72-day-old plants), data of various attributes were collected. Generally, salt stress negatively affected the growth attributes in both maize cultivars. Furthermore, salinity increased relative membrane permeability (RMP), malondialdehyde (MDA), total soluble protein contents, free proline and sodium (Na+) contents, and the activities of peroxidase (POD) and catalase (CAT) in both maize cultivars. Foliar spray of TRIA enhanced growth, soluble proteins, nitrate reductase (NR) activity, total phenolics, and free proline and shoot K+ contents, while it decreased RMP and root Na+ contents in maize. Overall, cv. MMRI-Yellow showed greater tolerance to salinity compared with Hybrid S-515. Among the various TRIA levels, 5 µM was much more effective in increasing growth of maize plants under both normal and saline regimes.