Horticulturae (Oct 2021)
The Combined Effect of <i>Pseudomonas stutzeri</i> and Biochar on the Growth Dynamics and Tolerance of Lettuce Plants (<i>Lactuca sativa</i>) to Cadmium Stress
Abstract
Agricultural activities lead to the accumulation of cadmium (Cd) in the soil. It is necessary to identify effective and economical ways to reduce the soil Cd bioavailability. To achieve this, three bacterial strains, Pseudomonas stutzeri, P. koreensis, and P. fluorescens, were tested for tolerance and biosorption of different concentrations of Cd (0, 5, 10, 15, 20, and 25 mg L−1). During the 2020 and 2021 seasons, a pot experiment was conducted using four different soil amendments (control, biochar, P. stutzeri, and a combination) under four levels of Cd (0, 40, 80, and 120 mg kg−1) and assessing the effect on growth parameters, physiological modifications, antioxidant enzymes, and Cd accumulation in lettuce plants (Lactuca sativa cv. Balady). In vitro, the results showed that P. stutzeri was the most tolerant of Cd. Our findings in pot trials showed that T4 (biochar + P. stutzeri) was a more efficient treatment in terms of the growth parameters, with 452.00 g plant−1 was recorded for fresh weight, 40.10 g plant−1 for dry weight, 18.89 cm plant−1 for plant height, 6.03 cm2 for leaf area, and 20.48 for the number of leaves plant−1, while in terms of physiological characteristics, we recorded 1.29 mg g−1 FW, 0.35 μg g−1 FW, and 3.69 μg g−1 FW for total chlorophyll, carotenoids, and total soluble sugar, respectively; this was also reflected in the number of antioxidant enzymes and intensity of soil biological activities in soil treated with 120 mg kg−1 Cd compared with the control and other treatments in the first season. A similar trend was observed in the second season. Additionally, significantly lower Cd was observed in both the root (67%) and shoots (78%). Therefore, a combined application of biochar and P. stutzeri could be used as an alternative to mitigate Cd toxicity.
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