Effects of microcystin-LR, cylindrospermopsin and a microcystin-LR/cylindrospermopsin mixture on growth, oxidative stress and mineral content in lettuce plants (Lactuca sativa L.)

Abstract

Toxic cyanobacterial blooms are documented worldwide as an emerging environmental concern. Recent studies support the hypothesis that microcystin-LR (MC-LR) and cylindrospermopsin (CYN) produce toxic effects in crop plants. Lettuce (Lactuca sativa L.) is an important commercial leafy vegetable that supplies essential elements for human nutrition; thus, the study of its sensitivity to MC-LR, CYN and a MC-LR/CYN mixture is of major relevance. This study aimed to assess the effects of environmentally relevant concentrations (1, 10 and 100 µg/L) of MC-LR, CYN and a MC-LR/CYN mixture on growth, antioxidant defense system and mineral content in lettuce plants. In almost all treatments, an increase in root fresh weight was obtained; however, the fresh weight of leaves was significantly decreased in plants exposed to 100 µg/L concentrations of each toxin and the toxin mixture. Overall, GST activity was significantly increased in roots, contrary to GPx activity, which decreased in roots and leaves. The mineral content in lettuce leaves changed due to its exposure to cyanotoxins; in general, the mineral content decreased with MC-LR and increased with CYN, and apparently these effects are time and concentration-dependent. The effects of the MC-LR/CYN mixture were almost always similar to the single cyanotoxins, although MC-LR seems to be more toxic than CYN. Our results suggest that lettuce plants in non-early stages of development are able to cope with lower concentrations of MC-LR, CYN and the MC-LR/CYN mixture; however, higher concentrations (100 µg/L) can affect both lettuce yield and nutritional quality.

A new aspect of grassland vegetation dynamics: cyanobacterium colonies affect establishment success of plants

“…; L. sativa , Freitas et al. ). We summarized the findings of these studies for natural floras in Table and for crop species in Appendix .…”

The surprising world of cyanobacteria: cylindrospermopsin has a soil face

“…In fact, it was recently demonstrated that CYN presence in soil can significantly increase mineral content (including phosphorus) in lettuce Lactuca sativa (Freitas et al. ). Its potential regulation of external phosphorus sources may promote one but inhibit the other, adding to an already complicated system of interactions between terrestrial autotrophic organisms.…”

“…If it also "enslaves" soil microorganisms through up-regulation of their ALP activity can it simultaneously contribute to plant growth through an increase in bioavailable phosphorus, which (similarly to aquatic ecosystems) is less abundant than nitrogen? In fact, it was recently demonstrated that CYN presence in soil can significantly increase mineral content (including phosphorus) in lettuce Lactuca sativa (Freitas et al 2015). Its potential regulation of external phosphorus sources may promote one but inhibit the other, adding to an already complicated system of interactions between terrestrial autotrophic organisms.…”

Food crops irrigated with cyanobacteria-contaminated water: an emerging public health issue in Canada

“…There is clearly an increasing risk of foodborne illnesses via food crops, and due consideration should thus be given to the water used to irrigate crops. While this risk has historically been due to the role fresh produce plays in the transmission of enteric pathogens, there is a growing body of evidence showing the potential for food crops to bioaccumulate cyanotoxins (Codd et al, 1999;McElhiney et al, 2001;Mohamed and Al Shehri, 2009;Hereman and Bittencourt-Oliveira, 2012;Freitas et al, 2015;Liang and Wang, 2015;Bittencourt-Oliveira et al, 2016;Cordeiro-Araújo et al, 2016;Machado et al, 2017a), potentially resulting in consumer exposure. …”