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<p>Root-mediated allelopathy is crucial in plant-soil interactions, particularly in continuous cropping systems. This study investigated the concentration-dependent allelopathic effects of the root aqueous extract (RAE), rhizosphere soil (RS), and root powder/residue–amended soil (RPAS/RRAS) of <i>Nicotiana tabacum</i> on two leguminous crops, <i>Cicer arietinum</i> and <i>Pisum sativum</i>. Bioassays conducted under controlled conditions revealed significant reductions in germination, seedling growth, photosynthetic pigments, and carbonic anhydrase and nitrate reductase activities. In contrast, proline accumulation, malondialdehyde content, and antioxidant enzyme (SOD, CAT, and POX) levels were significantly elevated, indicating oxidative stress induction and activation of defense responses. Rhizosphere soil from tobacco also impaired the growth and physiological parameters of both crops, suggesting the persistence of phytotoxic compounds in the soil. Cytogenetic analysis using <i>Allium cepa</i> root meristems revealed chromosomal abnormalities, and scanning electron microscopy revealed alterations in stomatal morphology. GC–MS profiling identified 25 compounds, including nicotine-related alkaloids and phytosterols, which may have contributed to the observed phytotoxicity. Although these compounds are known constituents of tobacco, their integration with physiological and cytological responses provides mechanistic insights into root-mediated allelopathy. These findings support the hypothesis that the accumulation of tobacco root-derived allelochemicals in the soil may contribute to soil sickness under continuous monoculture, potentially impairing the growth of subsequent crops.</p>

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Physiological and biochemical responses of Cicer arietinum and Pisum sativum and Cytogenetic Responses in Allium cepa exposed to root-derived extract and rhizosphere soil of Nicotiana tabacum

  • 期刊论文

  • 发表日期：

    2026年7月17日

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  • Nazish Akhtar,
  • Mo Shadab,
  • Farha Aijaz,
  • Uzma Parveen,
  • M. B. Siddiqui

摘要

Root-mediated allelopathy is crucial in plant-soil interactions, particularly in continuous cropping systems. This study investigated the concentration-dependent allelopathic effects of the root aqueous extract (RAE), rhizosphere soil (RS), and root powder/residue–amended soil (RPAS/RRAS) of Nicotiana tabacum on two leguminous crops, Cicer arietinum and Pisum sativum. Bioassays conducted under controlled conditions revealed significant reductions in germination, seedling growth, photosynthetic pigments, and carbonic anhydrase and nitrate reductase activities. In contrast, proline accumulation, malondialdehyde content, and antioxidant enzyme (SOD, CAT, and POX) levels were significantly elevated, indicating oxidative stress induction and activation of defense responses. Rhizosphere soil from tobacco also impaired the growth and physiological parameters of both crops, suggesting the persistence of phytotoxic compounds in the soil. Cytogenetic analysis using Allium cepa root meristems revealed chromosomal abnormalities, and scanning electron microscopy revealed alterations in stomatal morphology. GC–MS profiling identified 25 compounds, including nicotine-related alkaloids and phytosterols, which may have contributed to the observed phytotoxicity. Although these compounds are known constituents of tobacco, their integration with physiological and cytological responses provides mechanistic insights into root-mediated allelopathy. These findings support the hypothesis that the accumulation of tobacco root-derived allelochemicals in the soil may contribute to soil sickness under continuous monoculture, potentially impairing the growth of subsequent crops.