砷对烤烟氮代谢的影响

采用盆栽试验，系统研究了砷对烤烟全生育期氮代谢的影响。结果表明，砷毒害对烤烟的氮代谢有显著影响。砷降低了整个生育期的硝酸还原酶(NR)活性，抑制了烤烟对硝态氮(NO₃^--N)的同化；提高了全生育期的谷氨酰胺合成酶(GS)活性，增强了烤烟对铵态氮(NH₄⁺-N)的同化。砷提高了全生育期的谷氨酸—丙酮酸转氨酶(GPT)活性和天冬酰胺酶(Asparaginase, ASG)活性，以及现蕾以后的游离氨基酸含量，使烤烟的氮转化代谢旺盛。与此同时，砷降低了烤烟生育前期的蛋白质含量，随着生育进程的推进，又引起中、后期的蛋白质含量增加，最终导致烤烟蛋白质的积累，但使整个生育期的烟碱含量降低。

#Effects of Arsenic on Nitrogen Metabolism of Flue-Cured Tobacco (Nicotiana tabacum L.)

Arsenic, a high toxic heavy metal, is one of the most serious contaminants in soil and a potential threat to crop growth and human health. Nitrogen metabolism plays an important role in growth and development as well as in yield and quality of flue-cured tobacco. It is necessary to study arsenic toxicity to nitrogen metabolism of flue-cured tobacco. Therefore, a systematic experiment was conducted on the farm of Henan Agricultural University, Zhengzhou, China. using Yunyan 85 (Nicotiana tabacum L.) planted in 400 mm×340 mm plastic pots, with the treatments of five arsenic levels of 0(CK), 5, 20, 40, and 60 mg·kg^-1 added to sodium arsenate (Na₃AsO₄·12H₂O)] to determine the effects of arsenic toxicity on metabolism of nitrogen. The results showed that arsenic toxicity significantly affected nitrogen metabolism in flue-cured tobacco. On one hand, activity of nitrate-reductase (NR) during the growing period was reduced, and on the other hand, glutamine synthetase activity (GS) during the growing period was increased. These indicated that assimilation of NO₃^--N was inhibited and assimilation of NH₄⁺-N was enhanced by arsenic toxicity. The activities of both glutamate-pyruvate transaminase (GPT) and asparaginase (ASG) during the growing period, and content of the free amino acids after budding stage were increased, indicating that arsenic toxicity enhanced nitrogen transformation metabolism in flue-cured tobacco. In the mean time, compared with those in CK, protein content during the early growing stage and nicotine content during the whole growing period were decreased. However, protein content was increased during the middle and late growing stages.