| Chemical weed control is the important part of the modern agriculture, but inrecent years, the problem of herbicide phytotoxicity are becoming serious.Based onpretilachlor, butachlor, oxadiazon, pyrazosulfuron-ethyl, bispyribac-sodium,quinclorac and so on, study the rice morphology, growth, physiological and yieldindex changes under the condition of different dosage of herbicides treatment, providetechnological reference in right, rapid and early diagnosis of herbicide phytotoxicity.The results are as follows:(1) The rice, when treated on foliage with Butachor at EC200,300,400,500and600ml/667m2at the second day after rice seeding, would be seriously affected, itsplants being dwarfed, with tan plaques, slowly growth, an obvious reduction of rootsystem, biomass both the parts above and under ground.(2) Rice is easily damaged by Oxadiazon when treated on foliage at EC200,300,400,500and600ml/667m2t the2st day after rice seeding, the plants becomingdwarfed, leaf tips being withered, yellow or dark brown. The severe phytotoxicitycaused rice unnormally growth, leaflets distorted or rudimentary and significantlyreduction of the roots.(3) Compared with butachlor and oxadiazon, pretilachlor is relatively safe to beapplied in paddy. The rice plants were just slightly dwarf after being treated withpretilacchlor at200~300ml/667m2. When treated at400~600ml/667m2, however,the rice was seriously inhibited by the herbicide, the plants being serious dwarfed, itschlorophyll decreased and the leaves curly, and the growth of the rice thus wasseverely suppressed.(4) It is safe for rice to be treated with10%pyrazosulfuron-methyl on foliage at 15~20g/667m2at1.5~2leaves stage of rice, the rice grew normally, and plant height,root system, production index were not different from the control. However, whentreated with10%pyrazosulfuron-methyl at30~50g/667m2, the rice plants weredamaged seriously, showing obvious dwarf, root reduction, seeding scorch, thusresulting in the decreasing of the yield.(5) The rice plants, when treated on foliage with50%quinclorac at WP50,60,80,100and120g/667m2at the1.5~2leaf stage would be damaged, showing distortionof its young leaves, plants becoming dwarf, and the decreasing of its yields.(6) There were serious negative effects to the rice plants when treated on foliagewith13%MCPA-Na at300~500ml/667m2on rice in the1.5~2leaf stage. The plantsbecame dwarfed, fragile, easily broken and falling over. The yields in the treatmentsare also obviously lower than that of the control.(7) After being treated on foliage with48%bentazone at300~500ml/667m2onthe1.5~2leaf stage, the rice plants were damaged to some extent. The plants becamedwarfed, tan plaques showed on its leaves, the tissues on the apices and marginalareas of ite leaves died. The yields in the treatments are obviously lower than that ofthe control.(8) The rice plants treated on foliage with10%bispyribac-sodium at20~50ml/667m2on rice in the1.5~2leaf stage would be seriously damaged. ThePlants became severely dwarf, its tip withered with yellowish color. Under seriouscases, its young leaves crisped, lost chrolophyll and died, also its roots could not grownormally. Finally, its yields in the treatments are obviously lower than that of thecontrol.(9) It is safe for us to apply10%metamifop on foliage of rice in its1.5~2leafstage.The plant height, root system, fresh biomass aboveground, and yield indexes inthe treatments have no obvious difference from the control. While treated with10%metamifop at200~300ml/mu, the rices plants were damaged to some extent. Its plantbecame slightly dwarf, leaves lost chrolophyll on its medial parts. Though its rootswere not seriously inhibited, its yields were obviously lower than that of the control.(10) Serious inhibitory influences existed in the rice plants when treated on foliage with10%fenoxaprop-p-ethyl at20~50ml/667m2on the1.5~2leaf stage. Thedamages symptoms include plants being dwarf, its leaves whitening from the base totip, plants turning yellow to death. The yields in the treatments are obviously lowerthan that of the control.(11)50%quinclorac is a good herbicide to control barnyard grass in paddy.When being treated with55%quinclorac before2leaf stage, the rice plants are easilydamaged with the usage amount lower than100grams/667m2. The recommendeddosage of the herbicide for rice plants being applied before two leaf stage is50~80g/667m2.(12) The morphological and physiological indices of the rice plants wouldobviously changed after being treated with10%pyrazosulfuron-methyl at40g/667m2or more. These indices include plant height, the maximal quantum yield ofphotosystem â…¡, the length, total surface area, volume and tip number of roots, aswell as the content of MDA, soluble sugar, and praline. While its chlorophyll content,root average diameter did not vary much.13) Its physiological and botanical indices, except the content of MDA, wouldvary much after rice plants were treated with10%bispyribac-sodium. These indicesinclude plant height, aboveground fresh biomass, maximal quantum yield ofphotosystem â…¡, the content of proline, soluble sugar, and chlorophyll of the leaves.Keywords: herbicide phytotoxicity; diagnosis; the circumvention technology;Pre-emergency herbicides; Post-emergency herbicides... |
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