Metribuzin Phytotoxicity Impact On Growth,Physiological Characteristics And Yield Of Soybean

The pot experiment to study the sensitivity difference and phytotoxicity symptoms among four major soybean varieties (’Hefeng-55’、’Heihe-48’、.’Dongnong-48’、.’Dongnong-52’) in Heilongjiang province to metribuzin in2012、2013;Through the test, resistance variety’Dongnong-52’was screened out as material to study the effect of metribuzin on growth, physiological characteristics and yield of soybean applied metribuzin6、4、1days before soybean emergence. The results were as follows:1. The sensitivity of four soybean varieties to metribuzin were different.’Heihe48’、’HeFeng55’were the most sensitive varieties,50%soybeans were damaged and10%-20%were dead at the recommended dosage;’Dongnong48’took second place and no damage was found at the recommended dosage, but50.1%soybeans were damaged and15.6%were dead when the application rates were1155g a.i./hm2;’Dongnong52’showed the highest resistance, phytotoxicity symptoms first appeared when the application were over1575g a.i./hm2, but no death at this application rate.2. The phytotoxicity symptoms of metribuzin presented with turning yellow of edge of seminal leaf or true leaf at VC stage of soybean, sometimes the whole true leaf turned yellow when the phytotoxicity seriously; The phenomenon of seedlings died majority occurred before the V4stage. The phytotoxicity symptoms presented on lower leaf at first and then on upper leaves of injured soybean plant with soybean growing.3. The influence rules on growth, physiological characteristics and yield were similar after applying metribuzin at three periods before emergence.However, the influence degree was different. Generally speaking, the sequence of influence degree of metribuzin was4d<1d<6d before emergence.4. Metribuzin phytotoxicity leaded to the damage of photoreaction center, the decline of photosynthetic capacity (Fv/Fm was declined), the imbalance of absorbed light distribution (Y (NO) was increased), the reduce of chlorophyll content and effective functional leaves, moreover, the accumulation of MDA content. Metribuzin phytotoxicity also leaded to destruction of the leaf antioxidant system. The activity of SOD increased at first and then decreased with the increase of formulation rates. The rangeability of various index increased with application rates increasing, and reduced with soybean growing. The effect of low concentration metribuzin-treatments on growth and development in soybeans showed promoted at first and then inhibited, and high concentration metribuzin-treatments showed inhibited over time after application. 5. The agronomic characters of soybean showed no significantly difference compared with control at the lower application rates, however, high concentration metribuzin-treatments leaded to reduction of branch number, main stem node and node of lowest pod heighten, and then reduction of effective pod and seed number per plant number per plant, finally caused yield reduced. Metribuzin had no significant effect on100-seed weight of soybean.