PHYSIOLOGICAL AND YIELD RESPONSES OF RICE TO FOLIAR APPLIED AUXINS

Abstract

A field experiment was conducted at the University of Agriculture Faisalabad to evaluate the effects of foliar-applied indole-3-acetic acid (IAA) on the physiological performance and yield of rice (Shaheen Basmati). The study employed a randomized complete block design with four treatments: control, 10 µM, 20 µM, and 30 µM IAA, applied at tillering and panicle initiation stages. Physiological parameters and yield components were assessed to determine auxin's efficacy. Results showed that foliar IAA significantly enhanced chlorophyll content (from 35.2 to 46.1 SPAD units), photosynthetic rate (from 18.3 to 24.8 µmol CO₂ m⁻² s⁻¹), stomatal conductance (from 0.21 to 0.29 mol H₂O m⁻² s⁻¹), and relative water content (from 78.2% to 87.1%), with 30 µM showing the highest values. Yield-related traits were also markedly improved: tillers per plant increased from 10.2 to 15.1, panicles per plant from 9.6 to 13.7, and grains per panicle from 95.3 to 132.1. The 1000-grain weight rose from 22.5 to 26.3 g, and grain yield improved significantly from 4520 to 5985 kg ha⁻¹. Notably, no significant differences were observed between the 20 µM and 30 µM treatments for most parameters, suggesting that 20 µM may be the optimal concentration. These findings underscore the potential of foliar-applied auxin in improving rice productivity by enhancing physiological efficiency and reproductive success, offering a promising strategy for yield optimization under field conditions.