Abstract
Exposure to lead (Pb) can have serious toxic effects on the physiological and biochemical processes of plants. The chemical form of the metal determines the degree of its toxicity. In our research, we examined the effect of lead in the form of lead nitrate [Pb(NO3)2] and lead chloride (PbCl2) in concentrations of 12.5 mM and 25 mM on pine (Pinus sylvestris) seed germination. Nitrogen salt causes more severe changes than chloride salt. Increasing levels of electrolyte leakage, malondialdehyde, and hydrogen peroxide were detected during germination processes. The high levels of ROS lead to redox changes in the cell. We observed a reduction in the level of the reduced form of glutathione (GSH), and at the same time observed increased levels of the oxidised form of glutathione (GSSG) depending on the concentration and also the time of exposure to lead compounds. At the beginning of germination processes, the effective non-enzymatic activity of the antioxidant cycle was dominant, and at the late stage the enzymatic activity was noticed in the presence of Pb compounds. CAT activity significantly increased after Pb compound exposition.
Highlights
Germination is an important and complex process that ends with seedling emergence [1]
The energy of germination varied depending on the concentration used; in the control seeds, germination was observed on the third day, in the concentration of 12.5 mM on the fourth day, and on the fifth day for the 25 mM
Germination capacity was reduced by Pb ions for the 12.5 mM concentration, germination was slightly reduced by both Pb compounds, while in concentrations of 25 mM of Pb(NO3)2 the germination rate was less than 40% of the control; with a 25 mM concentration of PbCl2, the germination rate was around 50% (Table 1A and 1B)
Summary
Germination is an important and complex process that ends with seedling emergence [1]. Seeds produced by plants from temperate climate zones, before natural shedding, have developed tolerance to desiccation. The anabiosis phase ends in non-dormant seeds when proper environmental and physiological conditions for germination occur. Germination starts with imbibition; the catabolic and anabolic phase is required for seedling formation [1]. The process of germination could be inhibited by a natural occurrence, such as dormancy, and by abiotic factors like drought or pollution. Heavy metal concentrations in the environment including lead (Pb), increase year by year and have a negative impact on human health, and on the proper functioning of ecosystems [2]. Pb is toxic to plants at even low concentrations [4]
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