除草剂对水生植物的生理生态效应

首先研究了常用除草剂对水生植物的生理生态效应。结果表明在 12种除草剂中 ,乙草胺、丁草胺、艾割对紫萍 (Spirodelapolyrhiza (L .) Schleid)、金鱼藻 (Ceratophyllum demersum )生长影响显著。其后进行的丁草胺对金鱼藻生物量及生理生化影响研究表明 :金鱼藻生物量 (干重 )随丁草胺浓度的升高显著下降 ,处理后 16 d,两者呈显著的负相关。丁草胺处理后金鱼藻光合放氧速率明显下降 ,至 16 d,2、4、6、8m g/L处理分别比对照减少 36 .0 2 %、4 1.6 4 %、4 2 .74 %和 4 8.4 3% ;呼吸耗氧速率亦显著下降 ,4、6、8m g/L处理分别比对照下降 2 5 .87%、6 6 .6 4 %、6 7.94 %。呼吸耗氧速率的改变与丁草胺浓度呈极显著的负相关 ;丁草胺处理后金鱼藻叶绿素含量显著下降。谷胱甘肽 - S-转移酶 (GSTs)的变化也与丁草胺处理浓度有关 ,低浓度 (1m g/L )呈现先高后低 ,至 16 d显著低于对照 ,高浓度 (8mg/L )为先低后逐渐恢复。除草剂对水生植物的影响有可能影响整个水生生态系的功能。

Impact of herbicides on physiology and ecology of hydrophytes

The use of herbicides in China has increased faster than that of insecticides and fungicides since late 1980's. Herbicide application has covered almost all habitats, including crop fields, orchards, forests, parks and natural water body. Such a large-scale application might have transferred herbicide residues into aquatic ecosystems, resulting in disfunction of hydrophytes as primary producers in energy flow. This study was conducted to investigate the effect of 12 herbicides (i.e. acetochlor, butachlor, metribuzin, fuazifop-P-butyl, isoprotuin, benazolin-ethyl, MCPA, quinclorac, fenoxaprop-P-ethyl, 2,4-D, fluroxypyr, and cinmethylin) on the growth and development of two hydrophytes, Ceratophyllum demersum and Spirodela polyrhiza (L.) Schleid,which were collected from natural water body in suburbs of Yangzhou City, and to determine changes in chlorophyll content, photosynthetic rate, respiratory rate and glutathione-S-transferase (GST) of C. demersum in response to treatment of water body with butachlor at five different concentrations. The results showed that acetochlor, butachlor and cinmethylin significantly suppressed the growth and development of C. demersum and S. polyrhiza (L.) Schleid. The biomass (dried weight) of C. demersum under the laboratory condition of controlled temperature and illumination decreased with increasing butachlor concentrations at 12 days after treatment (DAT), though at 5 DAT and 10 DAT, the biomass did not change significantly, as compared to the control (untreated). At 16 DAT, even significant negative correlation was shown between the dried weight of C. demersum and butachlor concentration, fitting to the regression equation: Y=0.6638-0.03347X(r=-0.9167). The photosynthetic experiment demonstrated that the oxygen emitting rate of C. demersum following butachlor treatment declined significantly while the rate of the untreated control was relatively constant during test periods. At 16 DAT, the oxygen emitting rate of the samples treated with 2, 4, 6, 8 mg/L of butachlor reduced by 36.02, 41.64, 42.74 and 48.43% in comparison to the control, respectively. The oxygen emitting rate of C. demersum was negatively correlated with the concentration of butachlor treatment (r=-0.879). The oxygen consumption rate of C. demersum subjected to treatment at 4, 6 and 8 mg/L of butachlor also decreased by 25.87, 66.64 and 67.94% at 10 DAT, as compared to the control. Furthermore, the treatment of butachlor influenced other two physiological indexes of the hydrophyte as well. The chlorophyll content of C. demersum tended to decrease with increased butachlor concentration at 12, 14 and 16 DAT. The glutathione-S-transferase (GST) activity of C. demersum following the herbicide treatment varied with butachlor concentration. At a high concentration (8 mg/L), the GST activity was minimized at 5 DAT and then gradually recovered to a normal level at 12 DAT; at a low concentration (1 mg/L), the activity was significantly higher than that of the control and those of the samples treated with higher concentrations at 5 and 10 DAT, but significantly lower than that of control at 16 DAT. Since the GST is a detoxification enzyme, a butachlor-caused low activity indicates that the herbicide treatment can reduce the function of detoxification in C. demersum.