Spray irrigation with cyanobacterial toxin contaminated water
a potential risk for plants used in agriculture, using Medicago sativa L. as a model plant
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Beschreibung
Toxic cyanobacteria are a growing worldwide problem. Eutrophication processes in the aquatic ecosystem as well as the general rise of temperature are ideal starting positions for the massive growth of cyanobacteria. In arid and semi-arid areas surface water is very often used for spray irrigation of agricultural plants. Effects of cyanotoxins on crop plants are rarely investigated.
In this research, the uptake of cyanotoxins in seedlings of Alfalfa (Medicago sativa) as well as in several other crop plants was investigated. In all examined plants the uptake of toxin via the roots, and furthermore the plant internal transport of the toxin to the shoot and leaves could be shown.
An important factor influencing the toxin uptake is furthermore the soil texture.
A correlation of toxin binding, bioavailability and the amount of clay particles in the soil was found.
After uptake of the toxin in the plants, the toxin can influence a lot of biochemical reactions in the plants, such as the inhibition of phosphatases. Furthermore, the promotion of oxidative stress in M. sativa via cyanotoxins was shown. Oxidative damage measured as lipid peroxidation, as well as the activation of the plant-specific antioxidative defence using enzymes (e.g. superoxide dismutase, peroxidase, catalase), enzymes of biotransformation (e.g. glutathione S-transferase, glutathione reductase) and low molecular-weight substances, such as tococpherols was observed.
Influence on gene expression in M. sativa of different protein phosphatase subunits, and relevant genes in the tocopherol synthesis could be shown. This revealed a strong influence of cyanotoxins on plant metabolism. Effects on gene expression of protein phosphatases were caused even by spray irrigatiion of the whole plant with toxin-containing water.
A reduction in crop yield and a possible transfer of toxins in the human food chain is most likely. Measurement of high toxin concentrations in eatable cormus parts of some crop plants in the PR China at Lake Chao revealed toxin amounts high above the recommended levels of WHO. This underlines the high relevance of this work.
Autor*in
Anja Peuthert