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<p>Heavy metals affect the normal physiological, molecular and biochemical functions of plants by generating oxidative stress, osmotic and ionic imbalance, membrane disorganization and metabolic homeostasis. The exogenous application of biostimulants can be an effective and eco-friendly approach for amelioration of heavy metals from the soil. Therefore, the present study was conducted to ameliorate the adverse effects of lead (Pb) and cadmium (Cd) and stress resilience responses by exogenous application of melatonin and <i>Bacillus halotolerans</i> in <i>Brassica carinata</i>. Initially, screening was conducted to select the most suitable concentration of melatonin, Pb and Cd for <i>Brassica carinata</i>. In addition to this, heavy metal resistance for PGPR was also evaluated. The 0.7 mM Pb, 0.5 mM Cd and 0.03 mM melatonin concentrations were selected for the present study. The petri plate experiment was conducted to closely observe the effect of melatonin and PGPR on seed germination, roots and seedling biomass in <i>Brassica carinata</i> plants under cadmium and lead stress. The germination rate was the same for melatonin, PGPR and untreated control as <i>B. carinata</i> itself possesses an excellent sprouting rate. The maximum increase in the number of lateral roots was observed in PGPR (35%) seedlings followed by melatonin application (27%). The maximum shoot length (12%) was observed in seedlings inoculated with PGPR. The maximum fresh weight of seedlings was resulted by PGPR application (18%). Furthermore, the pot experiment was conducted in a completely randomized design. An increase in plant biomass by the application of melatonin and PGPR was recorded. The maximum root length (7%), leaf area (39%) and fresh weight of roots (14%) were observed by PGPR. Maximum chlorophyll a (13.4%) and carotenoids (30%) were recorded by the PGPR + Mel application as compared to the untreated control. Mel application resulted in maximum increase (19%) in chlorophyll b and total chlorophyll (15%) over the control. A decrease in MDA activity by the application of PGPR (5%), Mel (13%) and PGPR + Mel (11%) treatments was recorded. The maximum increase (25%) in relative water content was observed in the Pb + Cd + PGPR + Mel. Maximum increase (100%) in SOD activity in leaves was recorded by the Pb + PGPR + Mel application. The maximum increase (67%) in POD activity, PPO (65%) in roots and (72%) in PAL activity in leaves was observed in the PGPR + Mel application. The maximum increase (94%) in CAT activity was recorded by the Pb + Mel application. The results demonstrated a significant amount of Cd and Pb accumulation in plants tissues, specifically in roots and shoots. The Cd accumulation was particularly high in upper ground tissues (shoots) as compared to roots and soil. Whereas Pb accumulation was higher in roots as compared to shoots. The present study suggested that PGPR (<i>B. halotolerans)</i> and melatonin have the potential to enhance growth and improve stress resilience under Cd and Pb stress in <i>B. carinata</i> plants.</p>

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Application of Melatonin and Bacillus halotolerans Mitigated the Cadmium and Lead Induced Toxicity in Brassica carinata by Improving the Growth and Defense System of the Plant

  • 期刊论文

  • 发表日期：

    2026年1月12日

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  • Namra Batool,
  • Asia Nosheen,
  • Humaira Yasmin,
  • Rabia Naz,
  • Paul A. Correa,
  • Syed Muhammad Usman Shah Kazmi

摘要

Heavy metals affect the normal physiological, molecular and biochemical functions of plants by generating oxidative stress, osmotic and ionic imbalance, membrane disorganization and metabolic homeostasis. The exogenous application of biostimulants can be an effective and eco-friendly approach for amelioration of heavy metals from the soil. Therefore, the present study was conducted to ameliorate the adverse effects of lead (Pb) and cadmium (Cd) and stress resilience responses by exogenous application of melatonin and Bacillus halotolerans in Brassica carinata. Initially, screening was conducted to select the most suitable concentration of melatonin, Pb and Cd for Brassica carinata. In addition to this, heavy metal resistance for PGPR was also evaluated. The 0.7 mM Pb, 0.5 mM Cd and 0.03 mM melatonin concentrations were selected for the present study. The petri plate experiment was conducted to closely observe the effect of melatonin and PGPR on seed germination, roots and seedling biomass in Brassica carinata plants under cadmium and lead stress. The germination rate was the same for melatonin, PGPR and untreated control as B. carinata itself possesses an excellent sprouting rate. The maximum increase in the number of lateral roots was observed in PGPR (35%) seedlings followed by melatonin application (27%). The maximum shoot length (12%) was observed in seedlings inoculated with PGPR. The maximum fresh weight of seedlings was resulted by PGPR application (18%). Furthermore, the pot experiment was conducted in a completely randomized design. An increase in plant biomass by the application of melatonin and PGPR was recorded. The maximum root length (7%), leaf area (39%) and fresh weight of roots (14%) were observed by PGPR. Maximum chlorophyll a (13.4%) and carotenoids (30%) were recorded by the PGPR + Mel application as compared to the untreated control. Mel application resulted in maximum increase (19%) in chlorophyll b and total chlorophyll (15%) over the control. A decrease in MDA activity by the application of PGPR (5%), Mel (13%) and PGPR + Mel (11%) treatments was recorded. The maximum increase (25%) in relative water content was observed in the Pb + Cd + PGPR + Mel. Maximum increase (100%) in SOD activity in leaves was recorded by the Pb + PGPR + Mel application. The maximum increase (67%) in POD activity, PPO (65%) in roots and (72%) in PAL activity in leaves was observed in the PGPR + Mel application. The maximum increase (94%) in CAT activity was recorded by the Pb + Mel application. The results demonstrated a significant amount of Cd and Pb accumulation in plants tissues, specifically in roots and shoots. The Cd accumulation was particularly high in upper ground tissues (shoots) as compared to roots and soil. Whereas Pb accumulation was higher in roots as compared to shoots. The present study suggested that PGPR (B. halotolerans) and melatonin have the potential to enhance growth and improve stress resilience under Cd and Pb stress in B. carinata plants.