Effects of cyanobacteria producing microcystins on seed germination and seedling growth of several agricultural plants

Abstract

The effects of cyanobacteria aqueous extracts containing Microcystin-LR (MC-LR) on the seed germination and growth of Pisum sativum, Lens esculenta, Zea mays and Triticum durum were investigated. Experiments were carried out on a range of doses of the extract (equivalent to 0, 1.6, 2.9, 5.8, 8.7 and 11.6 mu g MC-LR/mL). The results confirm that these plants were sensitive to cell-free extracts of a toxic Microcystis and that germination inhibition was dose dependent. One-way analysis of variance (ANOVA) showed that P. sativum is the most sensitive tested species with a 97% germination rate reduction and L. esculenta was the most resistant. At the 8th day, the exposure to the microcystins (MC) resulted in a significant decrease of plant epicotyls length, roots length and a net inhibition of lateral root formation. It is concluded that MC could affect also terrestrial plants seedling germination and growth. Therefore, the use of water for irrigation contaminated by MC could exert negative biochemical effects on seed and plant metabolism which might influence the agricultural crops.

Nodularin, a cyanobacterial toxin, is synthesized in planta by symbiotic Nostoc sp.

“…Microcystins are known to disrupt many plant physiological processes, including CO 2 fixation, sucrose synthesis, starch storage (McElhiney et al, 2001) and photosynthesis (Abe et al, 1996;Pflugmacher et al, 2007) by inhibiting plant protein phosphatases (Peuthert et al, 2008). Microcystin and nodularin exposure causes oxidative stress and stunted growth in plants exposed to the toxin in the rhizosphere (Gehringer et al, 2003;Lehtimaki et al, 2011), as well as inhibiting germination and seedling growth of several agricultural plants (Saqrane et al, 2008). Accumulation of microcystin and nodularin has also been shown in plants irrigated with toxincontaining water (Mohamed and Al Shehri, 2009).…”

Phytotoxicity associated to microcystins: a review

“…Furthermore, the damage was irreversible to the most sensitive species (P. sativum) and reversible to the least sensitive (L. esculenta) (Saqrane et al, 2008).…”

Sensitivity of salad greens (Lactuca sativa L. and Eruca sativa Mill.) exposed to crude extracts of toxic and non-toxic cyanobacteria

“…Saqrane et al (2008) observed a germination of 74.7% for lentils (Lens esculenta), and only 3% germination for peas (Pisum sativum), when exposed to 11,600 µg.L -1 of MC-LR. In the present study, a concentration a thousand times less of MC-LR equivalent caused a 10% reduction in germination of lettuce, 3% more than the extract without the toxin.…”

“…Purified or crude extracts of microcystin not only reduce the germination of seeds of aquatic plants but also affect agricultural plants, such as peas (Pisum sativum L.), lentils (Lens esculenta Moench), maize (Zea mays L.) and wheat (Triticum durum L.) (Saqrane et al, 2008). Furthermore, the toxin interferes with the metabolism of the seedlings (Saqrane et al, 2009), causing necroses (Chen et al, 2004, M-Hamvas et al, 2003.…”