LIB spectroscopic and biochemical analysis to characterize lead toxicity alleviative nature of silicon in wheat (Triticum aestivum L.) seedlings

• Pb declined growth due to increased Pb uptake, which alters photosynthesis.
• Si protects seedlings against Pb toxicity.
• This was due to decreased uptake of Pb and thus improved status of nutrients and antioxidants.
• Thus results show involvement of the regulation of nutrients in alleviation of Pb stress.
• LIBS can be used for in-vivo detection of Si and Pb accumulation.

ABSTRACTThe responses of wheat seedling treated with silicon (Si; 10 μM) and lead (Pb; 100 μM) for 7 days have been investigated by analyzing growth, Pb uptake, chlorophyll fluorescence, oxidative stress, antioxidants and nutrients regulation. Results indicated that, Pb significantly (P < 0.05) declined growth of seedlings which was accompanied by uptake of Pb. Under Pb stress, fluorescence parameters: Fv/Fm ratio and qP were significantly (P < 0.05) decreased while NPQ was increased. Si addition alleviated Pb-induced decrease in growth and alterations in photosynthesis, and also significantly (P < 0.05) lowered Pb uptake. Under Pb treatment, oxidative stress markers: hydrogen peroxide and lipid peroxidation were enhanced while DPPH
• scavenging capacity and total phenolic compounds (TPCs) were decreased significantly, however, Si addition improved the status of antioxidants. The non-protein thiols (NP-SH) showed enhanced level under Pb stress. Pb stress considerably disturbed status of the nutrients as decrease in Ca, P, Mg, Zn and Ni contents while an increase in K, S, B, Cu, Fe, Mn and Na contents were noticed. Si addition maintained status of all the nutrients remarkably. The quickest method of element analysis: LIBS spectra revealed significantly lower uptake of Pb in seedlings grown under Si and Pb combination and same was correlated with the data of AAS. Overall results pointed out that excess Pb uptake disturbed status of nutrients, photosynthetic performance, antioxidant capacity, hence severe oxidative damage to lipids occurred. Further, Si supplementation successfully regulated these parameters by inhibiting Pb uptake hence maintained growth of wheat seedlings. Similar pattern of data recorded by the LIBS, AAS and ICAP-AES confirmed that LIBS may be one of the promising and authentic tools to monitor the mineral and metal distribution in the plants without hampering or disturbing the environment due to its eco-friendly and non-invasive nature.

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