科技 农药 把它们熏死

　　Tobacco extracts protect plants from pests and pathogens

　　烟草提取物可用于植物病虫害

　　THERE are, as Paracelsus put it, no poisons—only poisonous doses. That is certainly true of nicotine. The amount in a puff from a cigarette acts as a pleasant stimulus. The amount in a packet of 20, injected in one go, would kill you.

　　巴拉赛尔士曾说：世上其实没有毒药，所谓的毒药只是有毒性罢了(更正：所谓的毒性只是剂量变化引起的而已）。对于尼古丁，这当然是确切无疑的。吸一口烟你可能会觉得神清气爽，但如果一次性把一包20支的烟全下去（更正：但是如果一次性注射一包20支烟的尼古丁剂量），可是会要了你的命的。

　　The Victorians understood this and regularly used nicotine as a lethal poison—not for people (except in the minds of a few crime novelists) but for insects. The invention of modern, synthetic insecticides has more or less killed that practice off. But Cedric Briens of the University of Western Ontario is thinking of reviving it, and is also asking whether tobacco has any other pesticidal properties that might be exploited by the hard-pressed horticulturalist.

　　维多利亚时代的人明白这一点，并且逐渐把尼古丁当做一种致命毒药来使用（更正：并且已经把尼古丁作为一种常见的致命毒药来使用）——不是用来杀人（除了在一些犯罪小说家的构思中），而是用来杀虫。而现代合成杀虫剂的发明在一定程度上结束了尼古丁的使命。现在，西安大略大学的塞德里克?布里安则又在考虑重新启用尼古丁，同时在设法验证烟草是否具有一些穷困潦倒的园艺家曾苦苦追寻的杀虫效果（更正：同时在设法验证烟草是否还有其他杀虫功能，期望可为饱受病虫害之苦的园艺家所利用）。

　　To find out, Dr Briens and his colleagues at Canada's agriculture ministry ground up dried tobacco leaves using a blender and a sieve. They then heated the result in a pressurised, oxygen-free environment to distil out what they could in the form of a treacly oil. They tested this oil on 11 species of fungus and four types of bacterium that are common agricultural problems. They also tried it on the larvae of Colorado beetles, a notorious pest of potatoes.

　　为此，布里安博士和他在加拿大农业部的同事们用搅拌机和筛子将烟叶碾碎，然后将碾碎后的烟叶在高压、无氧环境下加热，提取出一种以粘稠油状存在的物质。他们用这种油对农业中常见的11种真菌和4种杆菌，以及一种常见的令人闻之生厌的马铃薯害虫——科罗拉多甲虫进行了试验。

　　As they report in Industrial and Engineering Chemistry Research, the researchers found that several pestilential organisms were affected by the oil. Specifically they discovered that Pythium ultimum, a fungus that attacks aubergines, peppers, lettuces, tomatoes and cucumbers as seedlings, Clavibacter michiganensis, a bacterium that kills young plants and deforms fruits, and Streptomyces scabies, a second bacterium, which causes potatoes to develop revolting scabs and for which no treatment currently exists, all stopped growing in the presence of the oil. The beetle larvae, too, were killed—though that was no surprise, since the oil contained a lot of nicotine.

　　他们的研究结果发表在《工业化学与工程化学研究》上。研究报告显示这种油对好几种有害的有机生物有作用。研究明确地发现，在这种油的作用下，危害幼苗期茄子、青椒、莴苣、番茄、黄瓜的真菌——腐霉病菌，可使幼苗致死、果实畸形的杆菌——马铃薯环腐病菌，以及另一种导致马铃薯烂痂病，且目前没有有效防治方法的杆菌——疥链霉菌，均被抑制生长。此外，甲虫幼虫也可被杀死——这其实是意料之中的，因为这种油里含有大量的尼古丁。

　　What was a surprise was that removing this nicotine did not diminish the oil's effectiveness against bacteria and fungi, and made it only marginally less effective against beetle larvae. The crude oil killed all of the larvae whereas the nicotine-free stuff left a fifth of them alive after two days. Clearly, there are other pesticides at work, and finding what they are is the next task. Meanwhile tobacco has proved itself a more useful substance than even the Victorians realised. Can its rehabilitation be far off?

　　但意料之外的是，将这种油去除后，对细菌和真菌的影响作用却并没有降低，只是对甲虫幼虫的作用在一定程度上减轻了。布满这种油的环境中，所有的甲虫幼虫都被杀死，散乱分布的情况下，两天后也只有五分之一存活。显然，其它具有杀虫作用的物质在起作用，下一步任务就是找出这些物质。这些发现证明了烟草不止可以用来做香烟，它甚至具有比维多利亚时代的发现更大的作用。如此，烟草的这种"复兴"还会远吗？