| Frequent outbreaks of blue-green algae blooms become a global environmental problem.Cyanobacterial toxins produced by blue-green algae have toxic effects on organism, evencause toxis death. Among cyanotoxins, microcystins (MCs) are the most widespread group,and also the most frequently identified toxins in bloom outbreaks. However, MCs can be intothe terrestrial ecosystem by irrigation and affects the growth of terrestrial plant, accumulatedin plant, even threat human health by food train. In fact, MCs concentration change with theseasonal outbreak of blue-green algae, the self-degradation and the adsorption of soli, so theaccumulation of microcystins, growth and photosynthesis in rice exposed to differentconcentrations microcystins (0,1,100,1000, and3000μg·L-1) for7days and then withoutmicrocystins for7days were studied. In this paper, the study established a novel experimentalmodel in lab-scale by using high performance liquid method, enzyme-linked immunoassay,the leaf area analyzer, root analyzer, photosynthesis rate and chlorophyllfluorescence analyzer.The results were as followed:(1) MCs at1μg·L-1promoted the growth of rice seedlings, and did not affect growth ofrice at blooting stage. MCs at100μg·L-1inhibited the growth of rice, especially worsenedgrowth of rice at seedling stage. After7-day revovery, the damage caused by100μg·L-1MCscan be alleviated, the restore effects on rice in blooting stage was better. The biomass and theyield of rice in mature stage was still lower than the control, indicating that the resore abilityis limited. Growth of rice treated with1000or3000μg·L-1MCs was still lower than those ofthe control, even worse than those of the exposure period, showing an irreversible damage ongrowth of rice.(2) The dose-effects and time-effects of MCs on photosynthesis of rice showed that MCsat1μg·L-1did not affect the Pn, ΦPSII, ETR, qP and qN of rice at seedling stage, but increasedthe F0, Fv/Fm, Chl a, Chlb and Chl. At blooting stage, Pn, Chl, Chl a, Chl b, Chl a/b, qP andqN have no change, while the F0, Fv/Fm, ΦPSIIand ETR increased. High concentrationmicrocystins (≥100μg·L-1) decreased the Chl, Pnand the fluorescence parameters, theconcentration of MCs was higer, photosynthetic parameters were worse, especially worsenedat seedling stage. In addition, fluorescence parameters of leaves in rice at blooting stage wereless sensitive to MCs stress. During the7-day recovery, unde the100μg·L-1MCs treatment,the photosynthetic parameters were lowest at8th day due to the hysteresis effects, but withthe recovery time prolonging, photosynthetic parameters were slowly close to those of thecontrol, showing that the damage can be alleviated, and the recovery ability of rice in bootingstage is stronger. However the photosynthetic parameters in rice treated with1000or3000μg·L-1MCs were lower than those of the control, even worse than those of the exposureperiod, SPII center irreversibly damaged.(3) The results measured by enzyme-linked immunosorbent assay showed that MCs canbe accumulated by the rice, and the MCs accumulation was higher with the concentration ofMCs increasing, positively correlated with MCs concentration. After7-day recovery, theaccumulation of microcystins in tissues was lower than that during the exposure period. In addition, MCs accumulation in various organs of rice seedlings is higher than those atbooting stage, possiblely due to the degradation of MCs and growing of plant. The order ofMCs accumulation in different organs is: root> leave> stem, while in recovery period, theaccumulation order of MCs was changed to leaves> roots> stem.The results imply that irrigation with microcystins-contaminated water must bemonitored and controlled. This also help people objectively evaluate the potential hazard ofMCs in agricultural production and food security. |
