砷对烤烟碳氮代谢及其产量和品质的影响

 采用盆栽试验，系统地研究了砷对烤烟全生育期的碳氮代谢及其产量和品质的影响。 结果表明，砷毒害对烤烟全生育期的碳代谢有显著影响，抑制了碳的同化和转化，降低了整个生育期的叶绿素含量、光合速率，造成了全生育期可溶性糖的积累，导致了生育后期淀粉含量的降低，最终使碳积累减少。砷毒害也改变了烤烟的氮代谢，造成生育前期氮同化能力的降低，表现出硝酸还原酶(NR)活性下降、总氮和蛋白质含量低于CK。砷毒害烤烟的氮转化表现活跃，提高了其中的游离氨基酸含量和谷氨酸-丙酮酸转氨酶（GPT）活性，最终导致烤烟生育中后期总氮和蛋白质的积累，但使整个生育期的烟碱含量降低。研究还表明，砷毒害降低了烤烟的产量和经济性状，增加了叶片中砷的积累，可溶性总糖含量的提高和糖氮比的协调虽好，但烟碱含量的降低和总氮、蛋白质含量的增加，以及糖碱比和氮碱比的失调，不利于碳氮代谢有关的化学品质形成。

EFFECTS OF ARSENIC TOXICITY ON CARBON AND NITROGEN METABOLISM AND THE YIELD AND QUALITY OF FLUE-CURED TOBACCO

Background and Aims Arsenic (As) exists ubiquitously in our environment and in various forms that can be harmful to human beings as well as agricultural crops. In order to study mechanisms of carbon and nitrogen metabolism in flue-cured tobacco, Nicotiana tabacum,contaminated by arsenic, systematic experiment was conducted on the farm of Henan Agricultural University, Zhengzhou, China. Methods Five arsenic treatment levels (0, 5, 20, 40, 60 mg?kg-1 (added as sodium arsenate Na₃AsO₄?12H₂O)) were used to determine the effects of rsenic toxicity on carbon and nitrogen metabolism and on the yield and quality of potted ( 400 mm×340 mm) flue-cured tobacco plants(Nicotiana tabacum L. cv. ‘Yunyan 85’). Key Results The results showed that arsenic toxicity inhibited assimilation and transformation of carbon, decreased chlorophyll content and photosynthetic rates, and caused the accumulation of soluble sugar content during the whole growth period, and the decrease of starch content during the last part of the growing period. Arsenic toxicity also altered nitrogen metabolism and resulted in a decrease in nitrogen assimilation capacity during the early growing stage. Nitrate-reductase (NR) activity, and protein and total nitrogen content were decreased compared with the control. Nitrogen transformations resulted in an increase in the content of the free amino acids and activity of glutamate-pyruvate transaminase (GPT), an accumulation of protein and total nitrogen during the middle and late growth stages, but a decrease in nicotine content during the whole growing period. The results also showed that arsenic toxicity lowered tobacco yields and their economic value, Although the sugar_nitrogen ratio and the increase of the total content of soluble sugars related to carbon_nitrogen metabolism was beneficial, the decrease of nicotine content and the increase of the content of protein and total nitrogen, as well as high sugar_nicotine and nitrogen_nicotine ratios were not favorable for the formation of leaves with high chemical quality. Conclusions Arsenic toxicity had significant effects on carbon and nitrogen metabolism during the whole growing period, and lowered yield and economic value of flue-cured tobacco. Besides, it was unfavorable for the formation of leaves with high chemical quality, and led to an accumulation of arsenic in the leaves. Therefore, it w as suggested that flue-cured tobacco not be planted in arsenic contamination regions.