Effects of cyanobacterial toxins and cyanobacterial cell‐free crude extract on germination of alfalfa (Medicago sativa) and induction of oxidative stress

Abstract

Cyanobacterial toxins have adverse effects on both terrestrial and aquatic plants. Microcystins are cyclic heptapeptides and an important group of cyanotoxins. When lake water contaminated with cyanobacterial blooms is used for spray irrigation, these toxins can come in contact with agricultural plants. During the exposure to these toxins, reactive oxygen species can form. These reactive oxygen species have a strong reactivity and are able to interact with other cellular compounds (lipids, protein, and DNA). Plants have antioxidative systems that will limit the negative effects caused by reactive oxygen species. These systems consist of enzymes, such as superoxide dismutase, catalase, and ascorbate peroxidase, and nonenzymatic substances, such as reduced glutathione or vitamins. The aim of the present study was to investigate the effects of cyanobacterial toxins (microcystins and anatoxin-a) and cyanobacterial cell-free crude extract on alfalfa (Medicago sativa) seedlings. Inhibition of germination and root growth was observed with toxin concentrations of 5.0 microg/L. Also, oxidative damage, such as lipid peroxidation, was detected after the exposure of alfalfa seedlings to the toxin. Reactive oxygen detoxifying enzymes were elevated, showing a marked response in alfalfa to oxidative stress caused by the exposure to cyanobacterial metabolites that might influence the growth and development of these plants negatively.

Responses and toxin bioaccumulation in duckweed (Lemna minor) under microcystin-LR, linear alkybenzene sulfonate and their joint stress

“…2a), especially at high exposure concentrations (MCLR ≥3 g/ml, or LAS ≥20 g/ml or their mixture ≥3 + 10 g/ml), indicating that individual and joint exposure to the two toxicants in L. minor triggered antioxidant reactions. Increased SOD activity with MCLR treatment was consistent with other results [11,[48][49][50], but little research has focused on SOD activity after LAS exposure [24]. SOD activity was more strongly reduced after 8 d exposure compared with 2 d (Fig.…”

Effects of microcystin-LR, linear alkylbenzene sulfonate and their mixture on lettuce (Lactuca sativa L.) seeds and seedlings

“…This increased SOD activity with MCLR treatment was consistent with results of Chen et al (2004), who demonstrated that lower concentrations of MCs (0.024-0.12 lg ml -1 ) significantly increased SOD activity in rice (Oryza sativa L.) seedlings, whereas higher concentrations (0.6-3 lg ml -1 ) only slightly increased SOD activity. Exposure to 5 lg l -1 MCLR for 2 h for the aquatic macrophyte Ceratophyllum demersum, or 7 days for alfalfa (Medicago sativa), significantly increased SOD activity (Pflugmacher 2004;Pflugmacher et al 2006). Furthermore, exposure to MCLR concentrations as low as 0.5 lg l -1 increased SOD activity in spinach (Spinacia oleracea) variants (Pflugmacher et al 2007).…”

“…Up to 8.4-25.0 lg ml -1 of total MCs has been reported in several bloom samples (Máthé et al 2007). In many countries, the cyanotoxin-containing water is used as an irrigation source (Chen et al 2004;Pflugmacher et al 2006Pflugmacher et al , 2007, and/or some cyanobacteria are directly discharged as organic fertilizers to farms (Chen et al 2006). Therefore, it is possible for a large amount of MCs to be released into cropland and crops may be at potential risk of exposure.…”

“…Therefore, it is possible for a large amount of MCs to be released into cropland and crops may be at potential risk of exposure. As a result, the risk of MCs to soil/cropland has received considerable attention from scientists worldwide (Chen et al 2004(Chen et al , 2006Pflugmacher et al 2006Pflugmacher et al , 2007Crush et al 2008).…”

Toxin-producing blooms of the cyanobacterium Microcystis aeruginosa in rainwater ponds in Saudi Arabia

“…Besides the effects of MCYSTs on animals and humans, water contaminated with MCYSTs that is used for irrigation may inhibit germination and plant growth causing crop failures (Pflugmacher et al 2006). The exposure of edible crop plants to MCYSTs is also a concern for human health, as the toxins can accumulate in plant tissues (McElhiney et al 2001, Jarvenpaa et al 2007) and be transmitted to humans through the food chain.…”