Effects of paddy herbicide residues on agronomic traits and physiological metabolism of tobacco

Objective To study the effects of residual herbicides in paddy field on following tobacco agronomic traits and growth in rice and tobacco rotation district.

Method Three common herbicides including quinclorac, bensulfuron methyl and MCPA-Na were applied to paddy field using 1/4 of recommended dosages. The dynamic changes of amylase, nitratereductase, invertaer, polyphenol oxidase and peroxidase in tobacco leaves were determined using DNS, in vivo test, colorimetric method and guaiacol method respectively. The effects of herbicide residues on tobacco symptoms, agronomic traits and physiological metabolism were obtained.

Result All three herbicides were harmful to tobacco from topping stage to mature stage.Quinclorac affected tobacco plant especially in leaf width with the inhibition rate of 58.56%, and it also greatly affected the activity of nitrate reductase and peroxidase. Bensulfuron methyl mainly affected the plant height and leaf width with the inhibition rate of 14.21% and 13.74% respectively and mainly affected the activity of amylase and peroxidase with little effect on the physiological activity of tobacco. MCPA-Na affected the plant height, leaf length and width with the inhibition rate of 36.03%, 32.57% and 36.65% respectively, and only affected the activity of peroxidase.

Conclusion Quinclorac, bensulfuron methyl and MCPA-Na should be avoided in rice and tobacco rotation system.