Alleviation of salt stress-induced adverse effects on maize plants by exogenous application of indoleacetic acid (IAA) and inorganic nutrients - A field trial

Abstract

The effects of indoleacetic acid (IAA) and inorganic nutrients (K and P) on some physiological parameters and kernel yield of maize (Zea mays L.) cultivar DK 647 F1 were investigated in two parallel experiments conducted in the same growth season in a saline field. Sodium chloride equivalent to 100 mM was added to the irrigation water and saline water applied to the field using a drip irrigation system. Indoleacetic acid was applied as foliar spray. Potassium and P were applied to the soil at the sowing time as mono-potassium phosphate at 200 kg ha-1. Salinity significantly reduced shoot dry mass, cob yield, total kernel yield, weight of 1000 kernels, chlorophylls "a" and "b" and relative water content in the maize plants, but increased proline accumulation, activities of the key antioxidant enzymes superoxide dismutase (SOD; EC 1.15.1.1), peroxidase (POD; EC. 1.11.1.7), catalase (CAT; EC. 1.11.1.6) and polyphenol oxidase (PPO; 1.10.3.1), and electrolyte leakage. However, application of K and P or foliar spray of IAA mitigated the adverse effects of salinity on maize plants. The most promising effect of IAA or K and P on alleviation of salt stress on maize was found when they were applied in combination. Leaf sodium (Na+) concentration increased substantially, but leaf K+, Ca2+ and P concentrations decreased markedly in the salt stressed maize plants. However, exogenous application of nutrients, IAA, or their combination considerably reduced Na+ concentration and significantly improved K+, Ca2+, and P levels in the salt stressed maize plants. The exogenously applied inorganic nutrient- or auxin-induced growth promotion in maize plants was found to be associated with increased photosynthetic pigment concentration and leaf Na+/K+ ratio, reduced membrane permeability, and altered activities of some key antioxidant enzymes such as SOD and CAT under saline conditions.