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41.
The relationship between foliar injury, nitrogen metabolism, and growth parameters in ozonated soybeans 总被引:1,自引:0,他引:1
A single 12 h ozone exposure peaking at 0.20 ppm proved phytotoxic to greenhouse-grown 'Cutler 71' soybeans at each growth stage tested from V5 to R6. Visible injury occurred within 40 h on the unifoliodate leaves and middle-aged and older trifoliolates while the younger leaves were free from toxicity symptoms. In some instances visible injury was accompanied by a decrease in chlorophyll and an increase in leaf diffusive resistance. Although nitrogen fixation was not significantly altered except at early pod formation (R3), and nitrate reductase activity was significantly reduced only if the ozone exposure occurred at the time of maximal enzyme activity (V5), nitrogen content of the leaves was reduced by ozone treatment. Shoot dry weight was not affected 40 h after ozone treatment, but root dry weight was significantly reduced. Plants grown with supplemental NO(3)(-) were more sensitive to ozone than those dependent on fixed nitrogen. At plant maturity, there was no evidence of an ozone effect on shoot, root, or seed dry weight, NO(3)(-) -grown plants showed a significant increase in growth and yield over N(2)(-) plants; but no ozone effect was observed, despite the increased foliar sensitivity. Multiple ozone exposures at growth stages V3, R1 and R3 exacerbated the effects noted with a single episode and also reduced nitrogenase activity (reflected in specific and total nodule activity) and shoot and root dry weight. At plant maturity, there was again no evidence of a significant effect of multiple ozone treatment on shoot dry weight or seed yield although root weight remained low. The results would tend to support the hypothesis that older leaves of soybean do not make a significant contribution to seed yield. Although they may be injured by ozone during the reproductive phases of growth, seed yield may not be affected if the younger O(3)-tolerant leaves remain functional. 相似文献
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John Brennan Gregg M. Kiihne 《Journal of Loss Prevention in the Process Industries》2009,22(6):757-763
The old saying, “what you don't know can't hurt you,” implies that ignorance is bliss. “A little knowledge is a dangerous thing,” may be closer to the truth; however, it is not the little that we know that is dangerous, but that which is not known. By design, the processes used in the chemical industry are reactive, and the intended reaction receives much scrutiny. However, other reactions occur, often unexpectedly, and possibly with severe consequences. The lessons we learn from these reactions must drive the improvement of our process development and technology management processes and the culture that shapes those processes, a culture of Technical Discipline.Technical Discipline, analogous to Operating Discipline in the manufacturing organization, is a culture committed to fully identifying and characterizing chemical and reaction hazards, and properly documenting and communicating those hazards to create a permanent knowledge and understanding within the organization operating that process.A culture of Technical Discipline will reveal reaction hazards that might otherwise remain unknown until being unveiled in a dramatic and unexpected fashion. Until you fully identify and characterize the hazards of the materials you handle in your processes…what you don't know can hurt you. 相似文献