Effect of Iron and Phytohormones Application on Antioxidant Enzymes Activity, Chlorophyll and Grain Yield of Maize in Iron-deficient Soil

The study investigated the effect of foliar application of gibberellic acid (GA3) and cytokinin on antioxidative enzymes, chlorophyll content and grain yield of maize. Three factor randomized block design (RBD) was used to carry out the investigation in experimental farm of Dr. Rajendra Prasad Central Agricultural University, Pusa, Bihar during 2012-13.

The field experiment was laid out in Fe-deficient soil (Fe < 0.5 ppm) with contrasting cultivars of maize. The factors were: i) Fe-efficient (Suwan) vs. inefficient cultivar (Shaktiman-3); ii) ‘control’ (no Fe-spray) vs. one soil application of Fe (20 kg ha-1) + two foliar spray of Fe as 0.5% ferrous sulphate at pre-flowering and 7-days after flowering; and iii) foliar application of phytohormones viz., GA3 at10 and 20 ppm; cytokinin at10 and 20 ppm and their combinations.

Application of Fe and phytohormones significantly increased enzymes activity like catalase, peroxidise and superoxide dismutase. The highest activity was observed with combined application of cytokinin + GA3 at10 ppm. For example, the value of catalase increased from 196.0 to 217.0 µmol/min/g fresh protein, and peroxidase from 90.0 to 103.0 Units mg-1 fresh protein. There were significant increases in chlorophyll content of leaves, and grain yield with combined application of cytokinin + GA3 at 10 ppm. The maximum chlorophyll content was recorded in ‘Suwan’ (32.7 SPAD value) having treatment Fe application plus GA3 + cytokinin at10 ppm each. Grain yield increased significantly from 58.6 to 64.6 q ha-1 in ‘Suwan’ provided with Fe application and GA3+ cytokinin at10 ppm each compared to control (50.3 q ha-1). Results indicated that phytohormones were involved in regulation of nutrient availability and conversely mineral nutrients influenced hormone biosynthesis suggesting a relationship between hormones and nutritional homeostasis.

Conclusion: Exogenous application of phytohormones could alleviate Fe deficiency stresses in maize and application of Fe and phytohormones acted synergistically. Hence, application of GA3 + cytokinin at 10 ppm may be done to alleviate Fe stress and to improve grain yield of maize.