The Allelopathic Effects of Tobacco (Nicotiana tabacum) on Germination and Growth of Wheat (Triticum aestivum) and Pearl Millet (Pennisetum glaucum)

Abstract

Introduction: Wheat and pearl millet are essential crops in global agriculture and contribute significantly to food security and nutrition. However, their productivity is often constrained by environmental challenges and allelopathic interactions. Nicotine and other tobacco leaf derived compounds can affect seed germination and early plant growth. Aims: This study examined the allelopathic influence of tobacco leaf leachates and residues on wheat and pearl millet under laboratory and pot conditions, with relevance to sustainable residue management. Materials and Methods: During the rabi seasons of 2022-2024, wheat (Triticum aestivum cv. PBW-343) and pearl millet (Pennisetum glaucum cv. HHB 67) seeds were collected, sterilized and used for the experiments. Mature dry leaves of tobacco (Nicotiana tabacum cv. K326) were collected and used to prepare tobacco leaf leachates at concentrations of 0.25%, 0.5%, 1%, 2% and 3%. Bioassays for seed germination, root length and shoot length were conducted in petri dishes, and pot assessments were conducted using sieved clay loam soil. Chlorophyll content and dry biomass were also measured. Inhibition percentages were used to compare the effects on both crops. The study also included qualitative phytochemical screening and Fourier transform infrared spectroscopy (FTIR) of the leaf leachates. Result and Discussion: The results demonstrated that tobacco leachates, particularly at 1%, reduced germination by approximately 72% in wheat and 76% in pearl millet relative to the control. Root growth was the most sensitive parameter, showing reductions of approximately 82% and 73% in wheat and pearl millet, respectively. Significant reductions were also observed in shoot length, chlorophyll content and dry biomass (ANOVA, P < 0.0001). The inhibitory effects were stronger under laboratory conditions than in pot experiments, suggesting the partial degradation, immobilisation or reduced availability of allelochemicals in soil. Pearl millet showed greater sensitivity than wheat in germination and seedling growth inhibition. The findings indicate that tobacco-derived phytochemicals have marked allelopathic activity and highlight the need for careful management of tobacco residues in agricultural systems.