Asian Journal of Current Research

Application of herbicide not only diminishes the weed activities but also influences crop physiological processes. The present study planned to evaluate the impact of pre and post emergence herbicides on physiological traits of two genotypes viz., MH-65 and MH-45, to examine the genotype specific behavioral pattern. Treatments given as per the recommended dose of pendimethalin, imazethapyr, quizalofop, and their combinations as compared to the control (no herbicide application) to analyze the relative water content (RWC), cell membrane stability (CMS), canopy temperature (CT), canopy temperature depression (CTD), chlorophyll content, and chlorophyll stability index (CSI). Results revealed that under control conditions, MH-65 recorded higher RWC (87.90%) and CMS (57.40%) than MH-45 (79.10% and 51.80%, respectively), indicating superior baseline physiological status whereas herbicide application showed significant decline in RWC, CMS, CTD, chlorophyll content, CSI and increase in CT in both genotypes. Maximum reductions in tested parameters were observed under combined herbicide treatments, particularly imazethapyr + quizalofop, where RWC declined to 45.30% in MH-65 and 40.60% in MH-45, while CMS decreased to 21.00% and 18.20%, respectively. Similarly, canopy temperature increased to 35.20–36.90 °C, whereas CTD declined to as low as 0.10–0.05 °C, indicating severe impairment of transpirational cooling. Chlorophyll content and CSI also showed marked reductions, with minimum values of 4.81mg g⁻¹ FW and 48.90% in MH-65, and 4.30mg g⁻¹ FW and 43.20% in MH-45. Genotype MH-65 significantly maintained lower CT and higher CTD, RWC, CMS, chlorophyll content, and CSI than MH-45, finally showed greater physiological resilience in response to different herbicide treatments. Thus, this study highlights the effectiveness of physiological traits as dependable markers for screening herbicide-tolerant genotypes and enhancing weed management practices.