ABSTRACT Mercury is among the most toxic heavy metals, exerting severe effects on plant growth and physiology. Understanding how plants respond to mercury stress is crucial for assessing ecological risk and developing remediation strategies. This study aimed to evaluate the impact of varying HgCl₂ concentrations on root and shoot length, chlorophyll content, and biomass of Paspalum scrobiculatum. Seedlings were exposed to 0.01, 0.02, 0.05, 0.07, and 0.10 ppm HgCl₂ concentrations for 14 days under controlled conditions. Root and shoot length were measured using a digital scale, chlorophyll content was quantified spectrophotometrically, and biomass parameters were recorded. HgCl₂ exposure caused a concentration-dependent decline in growth, chlorophyll content, biomass, and survival of Paspalum scrobiculatum. Shoot length decreased from 13.6 ± 0.3 cm in controls to 1.5 ± 0.2 cm at 0.10 ppm, while root length declined from 1.97 ± 0.20 cm to 0.50 ± 0.10 cm. Total chlorophyll content dropped sharply from 1.67 ± 0.04 to 0.36 ± 0.05 mg/g FW. Strong negative correlations (r = –0.9 to –1.0) were observed between HgCl₂ concentration and all growth and chlorophyll parameters. Fresh and dry biomass decreased by 59 % and 67 %, respectively, with a concomitant rise in tissue water content. Survival declined to 50 % at 0.10 ppm. Regression modeling estimated EC₅₀ values of 0.030–0.069 ppm across endpoints. Mercury stress in P. scrobiculatum impairs growth, pigment retention, and biomass allocation by disrupting cellular metabolism and promoting oxidative damage. Keywords: Mercury toxicity, Paspalum scrobiculatum, Chlorophyll degradation, Biomass reduction, Heavy metal stress
Kumar et al. (Fri,) studied this question.