Elevated auxin levels during the reproductive stage improve rice crop productivity and grain quality

A higher sterility percentage is a common characteristic in the rice crop nowadays due to soil moisture and elevated temperature stress. We hypothesised that an improved auxin level during the reproductive stage may overcome this issue in common rice cultivars. Various rice cultivars were grown in pots, and naphthalene acetic acid (NAA) was applied as a source of auxin with a variable concentration (0 (N₀), 20 (N₁), 30 (N₂), 40 (N3), and 50 (N4) µmol L⁻¹) at the reproductive stage. The results revealed that all the levels of NAA improved crop productivity in all the cultivars, while its higher level (40 µmol L⁻¹), i.e. N₃ along with cultivar V₂ (Punjab Basmati) gave supreme results. The NAA application elevated the auxin level in the plants and improved the content of antioxidants to overcome the oxidative stress in the rice crop. The improved physiological mechanism resulted in higher crop productivity in terms of grain weight, grain yield, and harvest index under the aforementioned treatment combination. Moreover, it improved the quality of rice grains, and a very low sterility percentage was recorded in the treatment with the NAA application. It was also reported that grain quality was also maintained even after cooking. Therefore, the foliar application of NAA at the reproductive stage may be a useful strategy for improving rice growth, morpho-physiological characteristics, grain yield, and quality attributes.