Improving Rice (Oryza sativa L.) Growth Through Exogenous Application of Gibberellic Acid and Cytokinin under Varying Zinc Levels

Background: Poor translocation of micronutrients especially zinc (Zn) within plants poses a significant constraint on the growth of cereal crops. The present study investigated the effect of various Zn application methods and plant growth regulators (gibberellic acid (GA) and cytokinin) on the growth of rice crop. Methods: The experiment was carried out using a split-split plot design with three replications to assess two rice varieties (SAVA 127 and PR 126) under three Zn application methods: no Zn application (Zn0), soil Zn application (Zn1) and soil + foliar Zn application (Zn2) along with four PGR levels: no PGR application (H0), 10 mg L-1 GA (H1), 10 mg L-1 cytokinin (H2) and 5 mg L-1 GA + 5 mg L-1 cytokinin (H3). Result: Plant height was increased by 14.4% in variety SAVA 127 with foliar spray of 10 mg L-1 GA along with soil + foliar Zn application method. Application of 10 mg L-1 cytokinin in combination with soil + foliar Zn application method significantly enhanced growth parameters, where number of leaves per plant, leaf area index (LAI) and dry matter accumulation (DMA) were increased by 18.7, 36.0 and 41.6% respectively as compared to control in the variety SAVA 127. On the other hand, the maximum number of tillers per square meter (6.7% higher than control) was noted in variety PR 126. Overall, combined approach of soil + foliar Zn application along with 10 mg L-1 cytokinin was found as a superior option in improving various growth parameters of rice varieties.