Effect of ethephon and low phosphorus application on drought tolerance of Zea Mays var Saccharata grown on marginal soil

Utilization of marginal soil for agriculture with limitation of water could drastically affects the plant growth and hence reduce crop yield due to unfavorable soil physical properties or depleted in soil nutrient. Application of commercially available plant growth regulator (PGR) combined with fertilizer could be promising instead of development of new drought tolerant crop variety. The application of PGR with phosphorus (P) fertilizer is a practical and effective preventive solution for crops to tolerate with drought and marginal soil conditions. The main objective of this study was to determine the effects of ethephon and P fertilizer to induce formation of root cortical aerenchyma (RCA) in sweet corn root system as drought tolerant mechanism when grown in marginal soil. Sweet corn hybrid was used as test crop and Rasau soil series as selected marginal soil. Commercially available PGR applied in this study was ethephon (2-chloroethylphosphonic acid) and Triple Super Phosphate (TSP, 46% P205) was used as single P fertilizer source. The first experiment results showed ethephon rates combined with standard sweet corn NPK fertilization grown on Rasau soil series increased sweet corn plant biomass at 134 ppm compared with control and plant nutrient concentration in roots and shoot tissues particularly Fe, Mn, Zn and Cu, respectively. Furthermore, application of ethephon with P fertilizer combinations significantly increased growth parameters such as plant height, plant biomass, chlorophyll content, total phenolic content and formation of RCA which able to reduce root respiration so that sweet corn could survive under water deficit condition during cultivation on Rasau soil series. Cortex cell of sweet corn collapsed with application of ethephon and low P fertilizer and xylem number was increased. Increasing of xylem number could help the sweet corn to have better water uptake during cultivation with formation of RCA reduce the root respiration so that the sweet corn could conserved more water. Furthermore, predicted rates of ethephon and P fertilizer that induced RCA formation and gave highest total biomass by quadratic equation model y=134.16 + 0.0639x – 0.0003x2 was observed at 134 ppm ethephon and low P fertilizer rate (45 kg P2O5 ha-1). In addition, growth and yield of sweet corn was improved under well watered condition with ethephon and low P treatment compared with standard P fertilizer. The combined application of ethephon with low P treatment before tasseling delayed the wilting symptom and total yield loss. The results highlight that RCA formation was drought tolerant adaptive root traits and improve soil-plant water uptake could be induced with application of ethephon and low P fertilizer at the vegetative stage. The sweet corn plant with RCA formation could efficiently conserved moisture from the soil so that the plant is able to sustain the biochemical process in plant at maximum level during water deficit condition thus less affected growth and yield.