Effect of irrigation with microcystins-contaminated water on growth, yield and grain quality of rice (Oryza sativa)

Irrigation with microcystins-contaminated water threatens growth and yield of crops and human health. Growth of rice at booting stage is crucial for the yield of rice at mature stage. Hence, we studied growth, yield and grains quality of rice as well as accumulation of microcystins in different tissues of rice at booting stage exposed to 1, 100, 1000, and 3000 μg L⁻¹ microcystins solution and then recovered (without microcystins). After a 7-day exposure, microcystins content in tissues was positively correlated with microcystins concentrations, and microcystins content in roots was the highest. In addition, microcystins content in grains of rice treated with 1, 100, 1000 and 3000 μg L⁻¹ microcystins was 4.9, 7.1, 12.6 and 21.2 μg kg⁻¹ dry weight, indicating that the microcystins in grains of rice treated with microcystins (≥1000 μg L⁻¹) could pose a threat to human health through food chain. Low concentration microcystins (1 μg L⁻¹) did not affect growth and photosynthesis, but high concentration microcystins (≥100 μg L⁻¹) inhibited growth and photosynthesis. After a 7-day restoration, growth and photosynthesis in rice treated with microcystins (≥1000 μg L⁻¹) were even worse than those during the exposure period. After maturity, yield of rice as well as protein and amylose content in grains of rice treated with microcystins (≥100 μg L⁻¹) were all lower than those of the control. Our results imply that irrigation with microcystins-contaminated water must be monitored and controlled to avoid harmful accumulation of microcystins and damage to crops yield.