MicroRna268-Mediated Zinc Homeostasis in Rice (Oryza Sativa L.): Enhancing Growth and Yield Under Different Methods and Timing of Zinc Fertilizer Application

Abstract

ABSTRACT Micro-RNA268 (miR268) plays an important role in modulating plant responses to different types of biotic and abiotic stresses. Zinc (Zn) has an essential physiological role in plants and is often deficient in crops. A study was conducted under controlled lowland (flooded) rice cultivation conditions to investigate the potential role of miR268 overexpression in modulating rice seedling resilience and yield in response to foliar Zn application. The rice seedlings were exposed to different Zn supplementation treatments: control (without zinc application), root dipping of seedlings in 0.5% zinc solution, basal application (30 kg ha−1), and foliar applications of Zn (0.5%) at 30, 45, 60, 75, and 90 days of transplantation. Different parameters such as growth characteristics, chlorophyll content, and yield metrics were systematically evaluated post-harvest. The study demonstrated that miR268 overexpression enhanced Zn uptake, with foliar Zn application (90 days) yielding the highest chlorophyll content (1.85%) and lowest oxidative stress (malondialdehyde, MDA: 1.25 nmol g−1 fresh weight, FW). Basal Zn application resulted in maximal Zn accumulation (roots: 29.6 µg g−1 dry weight, DW; shoots: 37.5 µg g−1 DW) and a 15.5% increase in 1000-kernel weight. These findings confirm miR268‘s central role in Zn homeostasis: foliar Zn at 90 days was most effective for enhancing photosynthesis and reducing oxidative stress, whereas basal application was superior for maximizing Zn accumulation and grains weight. Therefore, the optimal method depends on the target outcome, foliar application for stress protection or basal application for yield improvement-thus providing flexible management for Zn-deficient soils.