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Bacillus pumilus enhances the safflower (Carthamus tinctorius L.) growth under chromium stress by an antioxidative potential and nutrient acquisition

Muhammad Tariq Javed: Department of Botany, Government College University

<div>Chromium (Cr) is a significantly lethal metal and exerted negative effect on plant physiology and healthy developments. Free living soil bacteria like <em>Bacillus pumilus</em> can improve the plant growth and health in stressed environment including metal toxicity and are considered as defensive approach to mitigate the toxic effects. The current study is, therefore, aimed to check physiology, morphology, growth parameters as well as the capacity to tolerate the Cr stress in safflower (<em>Carthamus tinctorius</em> L.) based upon better nutrient homeostasis. Plants were grown in soil spiked with different concentration of K<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub> i.e. 0, 2, 4, 6 and 10 mg/kg soil with and without <em>Bacillus pumilus </em>inoculation. Higher Cr treatment levels decreased the plant fresh and dry weight as well as the photosynthetic pigments of <em>C. tinctorius</em>. The plant root and shoot Cr contents increased while nutrient (P, K, Ca, and Na) contents decreased with increasing Cr levels particularly at 10 mg/kg Cr treatment. However, the <em>C. tinctorius</em> plants maintained with <em>B. pumilus</em> inoculation prompted a significant increase in plant biomasses together with decreased reactive oxygen species and enhanced activity of cellular antioxidant enzymes under Cr stress as compared with their respective un-inoculated controls. In parallel, the inoculation with <em>B. pumilus</em> under Cr stress enabled the <em>C. tinctorius</em> plants to accumulate the nutrients (P, K, Ca, and Na). It can be concluded that <em>B. pumilus</em> inhibited the uptake as well as root to shoot translocation of Cr in <em>C. tinctorius</em> which in turn resulted in healthy plants under Cr stress. Hence, Cr stress can be significantly mitigated by <em>B. pumilus </em>inoculation to get healthy plants of <em>C. tinctorius </em>in Cr contaminated areas.</div>