| Widely use of herbicides not only bring enormous benefits to environment but also cause potential biological hazard. Sysbiotic nitrogen fixation system in soybean which composed of rhizobium and root had the role of fixing nitrogen, and surply large a mount of nitrogen nutrients for soybean growth and yield formation. Symbiotic nitrogen fixation was not only affected by rhizobia and host, but also significantly affected by environment. Imazethapyr is target herbicide which was widely used pre-emergence and post emergence to control many kinds of grass, Cyperaceae and broad-leaf weeds, its action target is acetolactate synthase (ALS). However there were seldom system research on nodule nitrogen fixation and nitrogen metabolism affected by Imazethapyr. This paper investigated the effect of imazethapyr on nodule nitrogenase and nitrogen metabolism. The aim of this paper was to give theory base for understanding the effect of imazethapyr on nitrogen fixation and nitrogen metabolism. This will have an important practical aim to solve the disadvantageous effects of nitrogen fixation and nitrogen metabolism after the herbicides application in soybean. Field experiment was conducted to study the impact of imazethapyr on nodule growth, nodule nitrogenase and nitrate reductase, the key enzyme of nitrogen metabolism, glutamine synthetase and nitrogen content in soybean. bellow results were conclued.1. After imazethapyr pre-emergence application at 67 days after treatment(DAT) the soybean nodule number was still significantly inhibited at 62.5ga.i./hm~2 and 250ga.i./hm~2 use rate, and the inhibiton ratio were 27.94% and 9.66%. After imazethapyr single leaf application, the soybean nodule number was continuously inhibited at 125ga.i./hm~2 use rate, and the inhibiton ratio were 8.36%~28.44%. At 30 DAT the inhibition of soybean nodule number was recovered at 62.5ga.i./hm~2 use rate. After imazethapyr sequential leaf application, the soybean nodule number was continuously inhibited at 62.5+62.5ga.i./hm~2 and 125+125ga.i./hm~2 use rate, and the inhibition ratio were 3.83% to 20.32% and 0.38% to 48.08%.The soybean nodule fresh weight was significantly inhibited after imazethapyr pre-emergence application. At 47 DAT and 61 DAT imazethapyr had no significant effect on nodule fresh weight at 62.5ga.i./hm~2 use rate, and the inhibition of nodule fresh weight was peaked at 67 DAT and the inhibition ratio was 17.09%. After imazethapyr single leaf application at 10 days the inhibition of nodule fresh weight reached the highest level at 62.5ga.i./hm~2 and 125ga.i./hm~2 use rate, and the inhibition ratio were 18.59% and 23.09%. After imazethapyr post emergece treatment the inhibition of nodule fresh weight was recovered at 24 to 30 DAT. After imazethapyr sequential leaf application at 9 DAT the inhibition of nodule fresh weight was peaked at 62.5+62.5ga.i./hm~2 use rate, and the inhibition ratio was 25.92%. The inhibition of nodule fresh weight peaked at 125+125 ga.i./hm~2 use rate at 31DAT and the inhibition ratio was 38.84%.2. The soybean nodule nitrogenase was inhibited significantly after applying imazethapyr, and the nitrogenase activity reduced the performance of the law with the increased application of imazethapyr. After imazethapyr pre-emergence applied at 75 DAT the inhibition of the soybean nitrogenase activity peaked at the use rate of 62.5ga.i./hm~2, 125ga.i./hm~2 and 250ga.i./hm~2, and the inhibiton rates were 68.48%, 68.86% and 77.41%. After imazethapyr single leaf application at 30 DAT the inhibition ratio peaked at the 125ga.i./hm~2 use rate, and the inhibiton ratio was 70.83%. At 38 DAT the inhibition ratio at 62.5 ga.i./hm~2 use rate reached highest level, and the inhibiton ratio was 55.70%. After imazethapyr sequential leaf application at 23 DAT the inhibition ratio peaked at 62.5+62.5ga.i./hm~2 and 125+125ga.i./hm~2 use rate, and the inhibitory rates were 80.42% and 75.47%.3. The nitrate reductase activity of soybean roots and leaves were inhibited significantly after applying imazethapyr. After imazethapyr pre-emergence applied at 75 DAT the inhibitory rates of the root nitrate reductase activity were 44.98%, 64.26% and 53.26% 62.5ga.i./hm~2, 125ga.i./hm~2 and 250ga.i./hm~2 use rate. At this time only the imazethapyr at 250ga.i./hm~2, nitrate reductase activity of the leaf was still significantly inhibited, and the inhibitory rate was 8.99%. After imazethapyr postemergence applied the inhibition on root and leaf nitrate reductase activity was not inhibitied until 38DAT. After imazethapyr single leaf application at 38 DAT the inhibitory rates of the root nitrate reductase activity were 57.90% and 64.70%, and for leaf was reduced to 25.29% and 48.79% at 62.5ga.i./hm~2 and 125ga.i./hm~2 use rate. After imazethapyr sequential leaf application at 38DAT the inhibitory rates of the root nitrate reductase activity was 47.81% and 69.56%, and for leaf was reduced 78.44% and 10.15% at 62.5+62.5ga.i./hm~2 and 125+125ga.i./hm~2 use rate.4. The glutamine synthetase activity of soybean was inhibited significantly by imazethapyr. After pre-emergence applied at 61 DAT the inhibition of the soybean root glutamine synthetase activity peaked at 62.5ga.i./hm~2, 125ga.i./hm~2 and 250ga.i./hm~2 use rate, and the inhibiton ratio was 27.41%, 28.01% and 24.33%. At 67 days after treatment(DAT), the inhibition of soybean root glutamine synthetase activity was recoved. Inhibition of leaf glutamine synthetase activity was continuously inhibitied in the determination of 75 DAT.After imazethapyr single leaf application at 18 days, the root glutamine synthetase activity was not significantly inhibited at 62.5ga.i./hm~2 and 125ga.i./hm~2 use rate until 38 DAT. At this time, the inhibition ratio of the soybean root glutamine synthetase activity was 24.22% and 30.92%, and the inhibiton ratio of soybean leaf glutamine synthetase activity was 10.71% and 9.48%. After imazethapyr sequential leaf application at 23 DAT, the soybean root glutamine synthetase activity was continuously inhibitied by the imazethapyr at 62.5+62.5ga.i./hm~2 and 125+125ga.i./hm~2 use rate, and the peaked inhibition was 28.44% and 27.90%. At this time, the inhibition ratio of the leaf nitrate reductase activity was 1.92% and 10.22%.5. The glutamate contents of soybean were significantly cut down by imazethapyr. After pre-emergence applied at 61 DAT, the peaked inhibition of the soybean root glutamate content was found at 62.5ga.i./hm~2, 125ga.i./hm~2 and 250ga.i./hm~2 use rate, and the inhibitory rates were 20.86%, 21.31% and 23.13% respectively. The inhibitory rates of the soybean leaf glutamate content was 15.06%, 10.87% and 19.61% respectively and the inhibitory rates of the soybean nodule glutamate content was 3.54%, 5.58% and 5.94%. After imazethapyr preemergence applied at 47 DAT and 75 DAT, the soybean root and leaf glutamate content had no effect at 62.5ga.i./hm~2 and 125ga.i./hm~2 use rate.After imazethapyr single leaf application at 18 DAT and 24 DAT, the peaked inhibition of soybean root and nodule glutamate content was found, and the inhibitory rates were 13.19%~14.83% and 20.86%~27.52%. At 30 DAT and 38 DAT, the inhibition of the soybean root and nodule glutamine synthetase activity was recovered. After imazethapyr sequential leaf application at 9 DAT, the inhibition of soybean root and nodule glutamate content all reached the peak level, and the inhibition of root glutamine synthetase activity was recovered at 23 DAT. At 38 DAT the inhibition of the nodule glutamine synthetase activity was recovered.6. Imazethapyr had a significant effect on the nitrogen contents of soybean leaf and seed. At 55 DAT the inhibition of soybean leaf nitrogen content reached the peak level at 125ga.i./hm~2 use rate, and the inhibitory rate was 11.41%. At 67 DAT the inhibition was recovered. After imazethapyr pre-emergence applied at 61 DAT the inhibition of the soybean leaf nitrogen content peaked at 62.5ga.i./hm~2 and 250ga.i./hm~2 use rate, and the inhibitory rates was 5.78% and 13.49%. The inhibitory rates of soybean seed were 15.86%, 25.31% and 29.96% respectively.After imazethapyr single leaf application at 18 DAT the inhibition of soybean leaf nitrogen content reached the peak level, and the inhibitory rates was 11.21% and 15.46%. The inhibitory rates of the soybean seed was 29.35% and 23.98% after imazethapyr single leaf application. After imazethapyr sequential leaf application at 9 DAT the inhibition of the leaf nitrogen content reached the peak level at 125+125ga.i./hm~2 use rate and the inhibitory ratio was 29.41%. At imazethapyr sequential leaf application at 15 DAT the peaked inhibition of leaf nitrogen content was found at 62.5+62.5ga.i./hm~2 use rate, and the inhibitory rate was 10.87%. The inhibition ratio of the soybean seed were 24.57% and 36.92%.7. Although at 62.5 ga.i./hm~2 use rate soybean yield was not affected by imazethapyr, but at 62.5ga.i./hm~2, 125ga.i./hm~2 and 250ga.i./hm~2 use rate the yield was significantly decreased and the reduction ratio was 9.44% and 23.85% respectively. Soybean yield was not significantly effected by imazethapyr single leaf application at 62.5ga.i./hm~2 use rate. However soybean yield was significantly cut down at 125ga.i./hm~2 use rate. Soybean yield was not effect after imazethapyr sequential leaf application at 62.5+62.5ga.i./hm~2. soybean yield was significantly decreased 17.78% by imazethapyr sequential leaf application at 125+125ga.i./hm~2 use rate.
|
PDF Full Text Request